How to Use Autofocus Effectively

*This post is going to be aimed at DSLR users, so all apologies to point and shoot owners (although parts of this may apply to you).

Autofocus Modes: Single vs. Continuous

Autofocus settings can be confusing, because they repeatedly used the same words in different combinations.  Let's start with autofocus mode, which controls how often the camera attempts to autofocus.

Single servo means that when you press the shutter button halfway down, the camera will focus once, and hold that focus as long as you hold the shutter button halfway down.  This is good for off-center compositions, since you can focus on your subject, and then reframe your shot without losing your original focus.

Continuous servo (AI servo for you Canon users) means that when you press the shutter button halfway down, the camera will focus, and keep tweaking the focus as long as you hold the shutter button halfway down.  This is useful for maintaining accurate focus on moving subjects.

On more expensive DSLR's the focus mode switch tends to be on the front of the camera next to the base of the lens.  For example, on my Nikon D200 the available choices are "S" (single servo), "C" (continuous servo) and "M" (manual focus).  On entry-level cameras, this may be a menu setting instead.

BTW if the word "servo" is driving you nuts, just think "lens motor" instead.

Autofocus Area Modes: Single vs. Multiple

Very similar name, very different function.  Autofocus area mode controls WHERE the autofocus tries to focus.  Although the names can vary widely from brand to brand, they ultimately boil down to two types: single area and multiple area.

Before we get to that, look through the viewfinder of your DSLR.  You should see a matrix of small brackets or cells, as few as 3 or as many as 50.  These are the available autofocus areas for your camera.

In single area mode, only one of these autofocus areas can be selected at a time.  By default this is the one in the dead center of the frame, but you can cursor over to other brackets using the directional button on the back of the camera.  When you try to autofocus in single area mode, the camera will only attempt to focus on the one focus area that you have selected (if you're not sure which focus area is currently selected, it generally flashes red when you attempt to autofocus as a reminder).  The advantage of single area mode is it's predictability, although it can be slower since you must either move the focus area or "focus and reframe" for off center compositions.

In multiple area mode, the camera looks at all the autofocus areas and tries to decide where you think the subject is.  Obviously this can be hit or miss, but it's fast and can evaluate the entire frame at one time.  This is good for erratically moving subjects, quick-draw shots where you don't have time to focus, or "from the hip" shots where you can't see the viewfinder.

Autofocus area mode may be controlled by a switch or menu, depending on your camera.  Read your manual! :)

Focus vs. Release Priority

Another important autofocus setting.  In focus priority, the camera will not allow the shutter to release until autofocus "successfully" focuses on something (even if it wasn't your intended subject).  In release priority, if you press the shutter button all the way down, the shutter releases, in focus or not.

I spend all my time in focus priority, because it reminds me not to shoot if I can't establish a proper focus.  Release priority is good for "once in a lifetime" shots, where you won't get a second chance and you need to get SOMETHING, even if the focus isn't perfect.  However, release priority shoots no matter what, so you may get surprised by an image that looked in focus through the viewfinder, but wasn't quite so sharp when you got back to your computer.


Other Fancy Autofocus Stuff


Some cameras feature other specialized autofocus modes.  Predictive or tracking focus tries to anticipate the progress of a subject moving towards or away from you (such as a car) and adjusts the focus ahead of the object so that it will be properly focused by the time the shutter releases.  Some cameras also feature face recognition so that the camera knows to focus on the people instead of the background.  Another common one is "closest object" mode, which pretty much describes itself.  There are also a handful of other focus modes that may be particular to a certain camera, but they should all be a variation on or combination of one of the basic types listed above.

Autofocus (AF) Explained

Autofocus is just what it sounds like: the camera focuses the lens for you.

Passive vs. Active

Autofocus systems are broadly categorized as "active" or "passive".  

Active autofocus systems do not use the light coming through the lens to determine correct focus, instead they have a separate mechanism for determining the distance to the subject.  Some active autofocus systems use infrared light from two separate sensors to triangulate the position of the subject, others have sonar to "echo-locate" the subject like a bat.  Pretty slick, huh?  Well, active auto-focus is not commonly used in modern cameras.

Instead, most cameras now use "passive" autofocus.  All this means is that the camera analyzes the image coming through the lens to determine correct focus.  There are two ways this can be done, "phase detection" and "contrast measurement".

Phase Detection vs. Contrast Measurement

In phase detection, the camera uses mirrors and prisms to split the light coming through the lens into two similar images.  Because of the way the prisms are positioned in the camera, the images are focused slightly differently from each other.  The camera then compares the images to calculate the correct distance to the subject and focuses the lens.  Phase detection tends to be faster than contrast measurement and is the most common autofocus method used in DSLR cameras.

In contrast measurement, the camera analyzes the boundaries between light and dark areas of the image to determine correct focus.  While the image is out of focus, the boundary between a light and dark area will appear as a gradient (i.e. gradual change in brightness from one pixel to another, low contrast).  When the image is in focus, the boundary will be sharp (i.e. quick change in brightness from one pixel to another, high contrast).  The camera adjusts the focus until the image has the highest possible contrast, which corresponds to the edges in the image being in focus.

This is the method used in digital point and shoot cameras, most video cameras, and DSLR's when using the "Live View" or "Movie" modes.  Contrast detection is traditionally much slower than phase detection, although this technology is quickly improving.

Some Light Please?

As I mentioned above, almost all digital cameras use some form of passive autofocus.  Since passive autofocus relies on the light coming through the lens, the autofocus system can really struggle in dark environments.  To overcome this, many cameras have an AF-assist lamp, a LED that turns on whenever autofocus is engaged in a low-light situation.  However, autofocus still does best when the subject is brightly lit.  Autofocus can also struggle if your subject is strongly backlit (the sun is directly behind them), as it will struggle with the comparably dim light on your intended subject.

Not So Good Up Close

Autofocus also has trouble with very nearby subjects.  This is more of a concern for "macro" or close-up lenses on DSLRs, and also for point and shoot cameras which are sometimes able to focus from only inches away.  I couldn't tell you exactly what causes this problem, but it is a common and predictable problem for macro photography.  This is a great time to use manual focus!

Better Than You or I

Despite its limitations, autofocus generally focuses more accurately and consistently than people do, especially when it is used properly.  Most modern cameras are not optimized for manual focusing, and unless you have a big, bright viewfinder and excellent eyesight, you're probably better off using autofocus like the rest of us.

Up next, how to use autofocus properly!

Manual Focusing

Staying with our topic of lenses, let's get into focusing.

There are only two ways to go: manual focus and autofocus (often abbreviated "AF").  Let's cover manual focus first because it's simpler to describe, if more challenging to master.

Manual focusing is possible on every interchangeable lens I have ever seen (i.e. for SLR cameras), although most integrated lenses don't do this (i.e. those on point-and-shoot cameras).  On most interchangeable lenses, there is a focusing ring on the lens barrel, which you turn to manually focus the image.

On fixed focal length lenses (primes), the focusing ring is the only one on there.

On zoom lenses, the focusing ring is generally smaller than the zoom ring.  There it is, towards the bottom...

If it looks like there is only one ring on your zoom lens, look for a very small focusing ring at the very front of the lens.  See it?

Hold on, wait a minute before you start jerking the focusing ring around, I don't want to break your camera.  Many lenses don't allow you to manually override the autofocus without disengaging it first.  To do that, you'll need to flip the focusing mode lever to "M".  It's a little lever beside the lens mount, and generally the options are "M, S, C" (or just "M, AF").  If it's not on your camera body, it will be on the lens itself.  When you move it to "M", autofocus will be disabled, but you will be able to manually focus now (just don't forget to move it back when you're done).

On some newer lenses, they allow you to manually override the autofocus and turn the focusing ring whenever you want to.  Be sure to check your lens and camera manual to see if this is an option before you try it (for all the reasons I mentioned above!).  I can't speak for all brands, but the Nikon lenses that allow manual override have a "M - M/A" switch on the lens barrel.  M is manual only, M/A is autofocus with manual override.

So why focus manually?

Well, sometimes autofocus screws up.  Modern auto-focus is very, very clever, but just like automated exposure modes, it can't read your mind.  Also, manual focus can be very helpful if you are using an extremely shallow depth of field where only a tiny slice of the image is in focus.  For that reason it is preferred for close-up work where the DOF can get razor thin.

To me, manual focus is just a fall back when autofocus doesn't do the job.  Some people use manual focus exclusively, but my eyesight is too bad for all that.  If I had a larger viewfinder on my camera, and some laser eye surgery, I might change my mind though. :)

Up next, autofocus mania!

365project.org

Sorry it's been so long since I've posted, loyal readers (all 1.5 of you).  I found a cool new photographic community online and got sucked in!

Go check it out and sign up today!  It's free, unlike most things that will improve your photography...

365project.org

Don't forget the .org, .com is some random guy.

BTW, a "365" is where you take one picture everyday for a year.  It's like committing to jog every morning for a year, you might not make it out every morning, but it sure as hell will make you a better runner.  Same concept, only with photos!  Join up!

"Which Lenses Should I Buy?"

This is one of the most common questions asked by new photographers, and easier to answer than it sounds.

Start with the Kit Lens

What's the kit lens?  It's the one that came with your entry level digital SLR.  99% chance its a 18-55mm f/3.5-5.6 which is the standard these days.  Why start there?

1. It's cheap (between $100 - $200 on its own, probably less as part of an entry level DSLR kit).
2. It's reasonably sharp.  Since this is the lens most people will start with, it's also how they will judge their camera and the brand as a whole.  Manufacturers know better than to start you off with a total piece of crap.
3. It's good for general photography.  This zoom range is going to cover 95% of your typical subjects.  18mm is wide enough to get decent landscapes and 55mm is tight enough to capture a headshot without being right in someone's face.

Buy a Fast Prime Next

Fact is, the kit lens leaves a lot to be desired in terms of maximum aperture.  In low light situations, you're either married to your pop-up flash (yikes!) or you're forced to jack your ISO through the roof and cope with the horrendous noise.

So what's the solution?  Get a fast prime, something with a maximum aperture like f/1.4, f/1.8 or f/2.  Besides giving you low-light performance, large apertures produce a very shallow depth of field which is great for emphasizing your subject and turning the background into a pleasing blur.

Fast primes come in a variety of focal lengths, but I'd recommend staying around 35mm or 50mm which tend to be the most useful for general photography.  So how do you choose, 35 or 50?  Try taping down the zoom ring on your kit lens at 35mm for a while, then 50mm.  Which one do you find more natural?  There's your answer.

The good news is they can be relatively cheap (about $200).  If you're worried about not being able to zoom, relax, you've still got your kit lens.  Also, you'll be surprised how often you choose to keep your fast prime on your camera and leave the kit lens in your bag.

Save Some Money, Evaluate Your Limitations


Your next lens purchase might cost you a couple dollars, so save up some money.  While you're doing that, evaluate your limitations.  Which of the following problems do you run into the most?

1. I can't zoom in far enough on distant subjects.  This probably means you're shooting sports or wildlife a lot.  The solution?  Buy a telephoto lens.  There are a number of inexpensive telephoto zooms out there, mostly in the 55-200mm or 70-300mm zoom range.  Don't expect a large maximum aperture, f/4 - f/5.6 is typical.  It's possible to get fast telephoto zooms (f/2.8 and under) but the price tag is always four digits, so you might wanna hold off on those.
2. I can't zoom in far enough / focus on very small subjects.  Then you need to buy a macro lens.  The key spec to look for is magnification ratio: you want "1:1".  This is the realm of true close-up photography.  They tend to come in 50mm, 100mm and 200mm varieties (roughly).  The longer the focal length, the further away you can be and still get 1:1 magnification.  The longer focal lengths also cost more, so unless you are photographing poisonous snakes you'll probably be fine between 50 - 100mm.  Get ready to pay though, a decent macro lens starts at $400.
3. I can't zoom out far enough to get the whole scene.  Uh oh, you need a super-wide angle lens.  The general rule is, the wider the better.  10mm is better than 12mm is better than 14mm, etc.  You can always crop in later, and the whole reason to buy a super-wide angle lens is to get a SUPER wide view!  Keep an eye out for fisheye lenses when you're shopping, they are a different animal.  If you don't mind a distorted perspective, fisheyes are fun, but they aren't going to give you straight lines like a traditional wide-angle lens.
4. I keep having to change lenses.  Maybe you need a super zoom.  They can encompass a very large zoom range (such as 18-200mm) and give you the flexibility to capture a lot of different shots quickly without stopping to change gear.  Be warned, you get what you pay for.  The cheap super zooms are pretty junky, I suggest you spend a bit more to get real quality.

See, buying a lens isn't that hard!  There are a million choices out there, and it's easy to spend a crap load of money, so do your research before you buy!  Happy lens shopping everyone!

Mrs. Davis Speaks: Let's talk editing!

Hi everyone.  My sweet husband and I have agreed to do a little switcheroo, and while he's posting on my blog today, I am posting on his.  Today I get to discuss my favorite thing about photography and that is editing!

Before my husband flips out let me say this, and you should adhere to this like the DH and I do: you should not not NOT rely on editing to save your photographs from mistakes that could have been fixed in-camera.  In fact, working and correcting mistakes in-camera is what makes you a photographer.  See honey, I do listen to you :-)

So let's get cracking!  While everyone thinks that editing (in the photographic sense) and Photoshop are synonymous these days, that couldn't be further from the truth.  Today there are a wide variety of programs out there from beginner to advanced, and you certainly don't need to start with Photoshop.  In fact, I barely use Photoshop and try not to unless I'm touching up a blemish on someone's skin.

If you have a Mac of any variety, then you've got iPhoto and at least until you get very familiar with photographic editing, you're all set.  This program has slider bars that allow for adjustments in exposure, contrast, saturation, color temperature, and a few extras.  I think the sliders are useful for beginners because they allow a lot of control and you can visibly see the difference you're making in the photo and adjust accordingly.  After experimenting over time, you will be able to know what every control does and what your photo needs.  From my personal experience, I feel that this program is absolutely fantastic for beginners and even allows a great means of importing, exporting, and storing your photos in an organized way.  I love organization, yes I do!  So you've got a Mac?  New to photographic editing?  Start with iPhoto.  Done.

Now while I'm unwilling to admit this (and find it an absolute travesty!!!!) most people are using PC's.  That's a Windows-based operating system, for the record.  I'm not an expert on PC's and don't pretend to be, but there are plenty of photo programs out there to get the job done.  So I will only discuss programs I am familiar with.  That said Picnik.com, Photoscape, and even Adobe Photoshop Elements (the intro version of Photoshop) are great programs that all run on PCs and have rave reviews all over the internet. Two of those are free and Elements is only 99 dollars.

Adobe Lightroom is my favorite program and I use it on my Mac, but it is designed for both Windows and Mac users alike.  This is definitely a "professional" program but I found it easy to use from the beginning.  Like iPhoto, it has slider bars for editing and is fairly self-explanatory.  When I first began using it, I had no clue what I was doing, but it didn't take long to figure out the concepts, how they applied to my image, and grasp the awesomeness that is Adobe Lightroom.  My highest praise is for this program because of one reason:  you can never outgrow it.  The simplest thing it does it edit photographs into beautiful masterpieces but it can also help you with a photographic website layout, printing, watermarking, you name it.  It's my personal Gold Standard.  You can tag photos by keyword,  organize them neatly, flag, rate, you name it.  But, of course, it's not free.  The going rate for the newest version is 299 dollars and while slightly steep, if you've outgrown your free program, I suggest this.  Why?  Because the workflow is easy and I am a self-professed lover of this intuitive and amazing program!

Now I know you want to know the scoop about Adobe Photoshop right?  "Photoshop" is a term used so often it makes me laugh.  I hear it used in all sorts of contexts--always a verb and never a proper noun.  So here's the skinny.  Photoshop is truly a photographic professionals' program.  Most would say it's the industry standard and maybe it is.  But honestly, it's pretty advanced.  Okay, extremely advanced.  And if you're reading this blog, I know you're not in that category just yet and I also suspect you don't want to spend $699 on this program when you've just dropped your first wad of cash on a dSLR.  Am I right?  So is it cool and can it do amazing things?  Absolutely!  But trust me when I say, it is not for you.  Not now, at least.

So now that you've read all that, I bet you're still confused.  Buying the right software is just as confusing as buying the right intro dSLR.  Here are my final choices, but feel free to do some research if you don't believe me.

• Just starting out? GO FREE!

-iPhoto (if you have a Mac, you're set)
-Photoscape
-Picnik.com

• Outgrown both those programs?  

-Adobe Photoshop Elements (99 dollars!)

• Going a little more pro?

-Adobe Lightroom



Editing software is great, because no photos ever have to look like this:

Or this:

Instead, they can look like a better version of how they are:

Isn't editing awesome?  And we've only just begun!

Since I do all the editing in our family, I'm sure I will be doing more guest posts on editing in the future.

Now back to your regularly scheduled programming with my husband....

Focal Length and Angle of View Illustrated

When it comes to angle of view, seeing is believing, so let's look at some example images:


Fisheye.  Probably a bad one to start with, since this is the only situation where focal length does NOT translate directly to angle of view.  A fisheye is as wide as you can go, in this case a 180 degree angle of view (when measured diagonally across the frame).  Still, it makes sense to start here since this is as wide-angle as you can get...

Ok now on to normal "rectilinear" lenses that won't distort the world like a fun house mirror!  I'm going to label these starting with the actual focal length of the lens, followed by the equivalent focal length for 35mm film that would produce the same angle of view.  Remember, 35mm film is still used as the "gold standard" when comparing angle of view (see the last post if you need a refresher).


10mm (equivalent to a 15mm focal length on a 35mm film camera).  This is about the widest you can go without a fisheye and is considered a "super-wide angle" lens.

12mm (equivalent to a 18mm focal length on a 35mm film camera).  Still "super wide-angle", but you can see we lost a lot of real estate in just two millimeters.  Compare the edges of this photo to the one above.

16mm (equivalent to a 24mm focal length on a 35mm film camera).  This is the end of the "super-wide angle" range.  Coincidentally, our cat Ping jumped up on the wall in the exact center of the frame.  You'll see her more later.

18mm (equivalent to a 28mm focal length on a 35mm film camera).  This was the beginning of the traditional wide-angle range before super wide-angle lenses were developed.

24mm (equivalent to a 35mm focal length on a 35mm film camera).  This is the end of the wide-angle range and the beginning of the "standard" or "normal" angles of view.

35mm (equivalent to a 50mm focal length on a 35mm film camera).  This is the middle of the standard / normal angles of view.

50mm (equivalent to a 75mm focal length on a 35mm film camera).  This is basically the end of the standard / normal angles of view and the beginning of the telephoto range.

70mm (equivalent to a 105mm focal length on a 35mm film camera).  This is in the beginning of the telephoto range, sometimes called a "short" telephoto.  Ping is really coming in handy at this point, good cat, please stay put!

105mm (equivalent to a 160mm focal length on a 35mm film camera).  We're starting to get pretty far into the telephoto range.  I am literally on the opposite end of the house from Ping.

135mm (equivalent to a 200mm focal length on a 35mm film camera).  This is the end of the traditional telephoto range and the starting point for "super telephoto".

200mm (equivalent to 300mm focal length on a 35mm film camera).  Ok, now we are in super telephoto land.  I also cannot BELIEVE Ping is still sitting there.

300mm (equivalent to 450mm focal length on a 35mm film camera).  This is the end of the road for me kiddies.  I can't afford a telephoto bigger than this.  They don't make amateur lenses longer than 300mm right now, and I have no intentions of spending $5000+ on a 400mm or longer telephoto lens!

THANKS FOR ALL YOUR HELP PING!!!  GOOD CAT!!!

Learning Lens Basics

You know what the best part is about having a SLR camera?  Interchangeable lenses!!!  This is a HUGE advantage over the fixed lenses that are on almost all consumer cameras.  Why?  Because lenses need to specialize in order to truly be great.  Even today, there is not a perfect "one lens solution" that can shoot every type of shot well.  However, before we can talk about different kind of lenses, we'll need to get familiar with a couple of basic concepts:

Zooms vs. Primes

There are two types of lenses, the kind that zooms in and out (zoom lenses), and the kind that don't (fixed-focal length or "prime" lenses).  If you just thought, "Why in the hell would I buy a lens that doesn't zoom?!?!" then keep reading.

Zoom lenses can be wonderful things, but they are tricky to engineer.  That can result in some compromises on sharpness, weight, cost, and other specifications.  On the other hand, primes are simpler to design and have less moving parts.  This can result in lower cost, lighter weight and often increased sharpness, although you sacrifice the ability to zoom.

Angle of View

Angle of view describes how wide an area the lens can "see" at one time.  A wide-angle lens is what nature photographers use to show sweeping landscapes.  The opposite of this is generally referred to as a "telephoto" lens (not a "narrow-angle lens" as one might expect).  The same nature photographer might use a telephoto lens to capture a tight shot of a bird in a faraway tree.  In the middle of this range are "normal" or "standard" lenses.  They are well suited for general photography and are often said to approximate the natural angle of view of the human eye.

Angle of view is specified in degrees, but you don't often see this written on camera lenses.  Instead, they give you focal length, which is a little more complicated.

Focal Length

A full definition of focal length is complicated and not that helpful (go see Wikipedia if you don't believe me).  What you need to know is, focal length affects angle of view.  The shorter the focal length, the wider the angle of view.  The longer the focal length, the narrower the angle of view.  Focal length is pretty much always given in millimeters, so a 28mm lens is much wider than a 105mm lens.

It's almost that simple.  The only complication is, angle of view is also affected by the sensor size of your camera.  I really have to use an example to explain this.  Nikon's digital SLRs have one of two sensor sizes: FX or DX.  The larger FX size is the same size as a frame of 35mm film.  The smaller DX sensors are 2/3rds that size.  As a result, a 28mm lens on the larger FX sensor gives the same angle of view as an 18mm lens on the smaller DX sensor.

To try to simplify things, 35mm film is used as the standard.  Lenses often say "equivalent to such-and-such focal length on a 35mm camera".  To keep with our Nikon example, a 18-55mm zoom lens designed for a DX camera may also say "equivalent to 28-80mm on a 35mm camera".  Not the best system, but its what we're dealing with.

Maximum Aperture

Back to something easier and more familiar!  Maximum aperture is the largest available aperture setting for a lens.  This is important because a large aperture can let in more light and therefore works better in low-light situations.  A f/1.4 maximum aperture is about the largest you'll see.  f/2.8 is the standard maximum aperture for expensive professional lenses.  f/4 to f/5.6 is typical among more affordable amateur lenses.

Minimum Focus Distance & Magnification

These are the important specs for close-up photography (flowers, etc.).  Minimum focus distance is just what it sounds like: the closest distance you can focus at.  This can be anywhere from a few inches to a few feet.

Magnification is how large the subject appears in the image compared to in real life.  A "1:1" magnification ratio is basically like you laid the object right on the image sensor.  So if your sensor is the size of a postage stamp, you could take a picture of a postage stamp and fill the entire frame with it.

Compatibility

Make sure the lens you buy is compatible with your camera!  Different brands of cameras have different types of lens mounts, so you need to make sure the lens will actually attach to your camera.  Sometimes that is only lenses with the same brand as your camera, but there are also manufacturers who make lenses for multiple different brands.  Even within a brand, some lenses are not compatible with certain cameras, or limit the features you can use (such as auto-focus, metering, etc.).  Do your research before you buy so you don't get a nasty surprise!

Vibration Reduction (VR)


This feature helps minimize vibration and reduce the dreaded "camera shake" at low shutter speeds.  Also called image stabilization (IS).

Recap

Here's an example of a lens you might see for sale online:  Nikon 18-55mm f/3.5-5.6 VR AF-S DX lens.  Confusing right?  Let's break it down:

Focal length: 18-55mm (this is a zoom)
Maximum aperture: f/3.5 - f/5.6 (this means the maximum aperture changes over the zoom range: f/3.5 zoomed all the way out, f/5.6 zoomed all the way in)
VR: Has vibration reduction.
AF-S and DX:   Two examples of compatibility specs, which differ from brand to brand.  Some Nikon cameras have to have AF-S lenses in order to auto-focus.  The DX means this lens is only designed to work on DX-sized sensors.

Up next, real talk about the types of lenses you want to buy.

Exposure in 7 Shots

Got 2 minutes?  ...like literally, 120 seconds?  Sweet.  Grab your camera, we're going to take 7 quick shots and demystify this exposure setting stuff once and for all.

Shot #1:

Pick up your camera and walk outside onto your front steps, breezeway, or whatever.  Just get outside.  Set your camera's Exposure Mode to Aperture Priority (for most cameras, this means turning the dial on top to "A").  Now, set your aperture to f/5.6.  Find something nearby to focus on, about 3 or 4 feet away.  I used the broken flag bracket on my front porch.  Make sure that whatever's in the background is decently far away, like your neighbors house or a tree across the street.

Next, look at your shutter speed.  To avoid screwing with more settings later, we want it to be about 125 right now.  If its lower than that, gradually increase the ISO setting on your camera until you end up somewhere between 100 - 160 on shutter speed.  If your shutter speed is higher than that, gradually step down your ISO until you get in that range.  Just to get you in the ballpark, if its bright and sunny outside your ISO will probably be 100 or 200.  If its cloudy or moving on towards dusk, it might be 400, 800 or maybe even 1600.

Reframe your shot, focus on the nearby object you chose, and pull the trigger.

Shot #2:

Change your aperture to f/16.  Reframe, focus on the same nearby object, shoot again.  That's it!

Now compare Shot #1 vs. Shot #2.  Notice that the nearby object (my flag bracket) is equally in focus in both images.  But look at the difference for the far away objects in the background.  They are blurry in the first shot, taken at f/5.6 (shallow depth-of-field).  They are much sharper in the second shot, taken at f/16 (deep depth-of-field).  Congrats, you now understand aperture's effect on depth of field!

Shot #3:

Turn around, open your door, and take a shot into your house.  Its much darker inside, so you should hear your shutter take its sweet time opening and closing.  Look at the picture and zoom in.  See how blurry everything is?  This is because you are hand-holding the camera at a very slow shutter speed.  What you're seeing is the dreaded "camera shake"!

Shot #4:

Walk back outside.  Set your camera's Exposure Mode to Shutter Priority ("S").  Set your shutter speed to 500 (1/500th of a second).  Hold out your free hand and focus on it.  Now pull your hand back, and swing it slowly through the frame.  Shoot when you see your hand in the middle of the viewfinder.  Check your shot.  See how your hand is frozen in place?  (If it's not, you were pretending to pitch a fastball, so slow down and try again.)

Shot #5

Set your shutter speed to 125 (1/125th of a second) and do that thing with your arm again.  Swing it the same speed, shoot when it hits the middle.  See how your hand is all blurry?  Now you understand how shutter speed effects moving objects.  Fast shutter speed = frozen in place.  Slow shutter speed = movement looks blurry.  Two more to go!

Shot #6

Set your camera's exposure mode to Program Mode ("P").  Change your ISO to 1600.  Shoot something, subject isn't as important this time.

Shot #7

Dial your ISO down to 100.  Reshoot the exact same shot.

Compare shots #6 and #7.  Zoom in allll the way on the same area in both shots.  See the grainy speckles in shot #6 (ISO 1600)?  That's noise.  See how much smoother everything is in shot #7 (ISO 100)?  Now you understand the affect of ISO on image quality!

DONE!

Exposure Compensation

Bad news... I've been holding out on you.  Now that I've made you learn all this stuff about metering and manually exposing your images I'm going to give you a shortcut.  An awesome shortcut you will use all the time like I do.  Nothing wrong with it, because sometimes saving time is the difference between getting the shot and missing it.

So what is it?  It's exposure compensation.  It's the quickest way to make an image brighter or darker and it works in every exposure mode except manual (so that would be aperture priority, shutter priority, program or any "scene" mode).

Here's how it works: exposure compensation starts set at "0.0".  All this means is that the camera will use whatever exposure settings the meter would normally come up with.  If you turn exposure compensation UP, i.e. set it to any positive value, the camera will automatically overexpose the image by that much.  "+1.0" will overexpose by a full stop, "+0.7" will overexpose by two thirds of a stop, etc.  On the other hand, if you turn exposure compensation DOWN, i.e. set it to any negative value, it will underexpose by that much.  "-2.0" would underexpose by two stops.  "-0.3" would underexpose by a third of a stop.  You get the idea.

So here's how you use exposure compensation.  Let's say you are taking a picture of a light-toned scene, say maybe snow or my light yellow dining room.  Since we now know how our camera's meter works, we know it will suggest exposure settings that would make the scene medium-toned (i.e. 50% gray).  To render our light-toned subject the way it actually looks, we will need to overexpose the image.  So, you just crank exposure up a stop or two ("+1.0" or "+2.0") and shoot.  Now hit play and check the results.  Two bright?  Crank it down a little.  Too dark?  Turn it up some more.

That's it.  It works for dark-toned objects too.  If you are taking a picture of your black desk, the meter is going to suggest exposure settings to make it gray.  If you want it to actually look black, turn exposure compensation down.  Check the results on the back of the camera, tweak the exposure comp and reshoot until you like what you're looking at.

THAT'S IT!  Its incredibly convenient, and fast, and easy to understand.  The more familiar you get with your camera's meter, the fewer times you will have to adjust and reshoot.  After a while, you will actually be able to predict how much or how little you need to over/under expose for a given scene.  It's also a great way to experiment with exposure.

Now, just for the hell of it, lets look at an example.  In this case the metered value (i.e. "0.0") was probably the closest to right, but you see how it works.  Exposure is somewhat subjective anyway, so maybe you like the one on the right better.  Click the image to enlarge for a better view.

Now I'll admit, the far right image is a little blurry due to camera shake, but you already know how to fix that, right?

Buying Your First SLR

Lets take a quick break from learning about exposure and talk about buying a camera.  The number one question I get from people is, "What camera should I buy?"


People who know a lot about photography looove to overcomplicate this question. While it's true that people have different needs and no single camera is right for everyone, its pretty easy to point someone in the right direction.

The fact is, if you're interested in taking up photography as a hobby and you ask me (or anyone else) what camera to buy, the unspoken part of that question is: "I don't know that much about photography yet, but I really want to learn.  I need a camera that will let me take pictures like the pros once I learn how to use it, and something I won't grow out of later on.  I also need something affordable since I'm just getting started and not 100% sure whether I'll stick with it or not.  What camera should I buy?"


The answer is: an entry-level DSLR kit.  DSLR stands for "digital single lens reflex" camera, just in case you were wondering.  What that means doesn't really matter, its honestly just trivia so I'm skipping it for now.  Also, when I say "kit" I mean it comes with a lens.  We'll get to that in a second though.

Ok, so there are basically 4 entry-level DSLRs on the market today that I would seriously consider:

1. The Nikon D3000
2. The Canon Rebel XS (or XSi)
3. The Sony Alpha A230
4. The Pentax K-x

In many ways they are very, very similar.  They all cost between $400 - $550.  They all have between 10 -12 megapixels (which is more than enough for anyone).  They all go up to at least ISO 1600.  They all have some form of vibration reduction which helps avoid "camera shake" at slow shutter speeds.  They all have maximum shutter speeds of 1/4000th of a second (which is fast enough for anyone).  They have all the exposure modes, metering modes and about every other type of setting or feature we will talk about.  You can take incredible pictures with any one of these cameras.

So how do you choose?

Well, as general consideration, try to think of this purchase as buying into a camera system, not just buying one particular camera.  The great thing about DSLR's is they have interchangeable accessories such as lenses, flashes, etc.  Once you start investing in a certain brand you're not just going to chuck all your old equipment and start over with another company.  You'll buy new lenses and accessories over time, and eventually when you're ready to upgrade or replace your current camera body, you'll buy a new camera of the same brand so it will be compatible with all your current lenses and accessories.

So what are these brands good at?  Nikon is famous for its lenses and accessories, while Canon is known for intuitive menus and great color rendering.  Pentax is a long-time maker of very popular entry-level SLRs aimed at students.  Sony has a lot of experience making image sensors and quality electronics in general.

Like I said above, these cameras have most of the same features and specifications in common, so here's a few reasons why you might choose one over the others.

Nikon D3000.  On paper it doesn't have anything the other cameras don't have, except a slightly larger LCD screen on the back.  However, it is a Nikon.  I know from experience that Nikon's 18-55mm lens is tack sharp, surprisingly holding its own against many of their more expensive products.  With this camera you're really buying into the Nikon system, and you basically have limitless room to grow with access to the best lenses and accessories in the business (OK, that's more of a personal opinion, but I'm not the only one who thinks so).  On the down side, it is the most expensive of the four cameras, but hey, you get what you pay for sometimes.

Canon Rebel XS.  Same specs as the Nikon on paper, and similar reasons to buy it.  You're buying into the Canon system, and as much as it pains me to admit, they have a huge variety of quality accessories also.  Canon also has very user friendly menus and, in my opinion, excellent color rendering.  I've seen these on sale recently for $500 with the lens included.

Sony Alpha A230.  Higher maximum ISO than the Nikon or Canon (3200 max instead of 1600).  That's a full stop, which honestly matters sometimes, and is a point in Sony's favor.  Also the cheapest of the group at $400.  I don't know if the build quality would be quite as good as the Nikon or Canon, and there aren't quite as many accessories available, but there's definitely everything you would reasonably ever expect to use.  If price is a serious concern, I'd pick this camera.

Pentax K-x.  Highest maximum ISO of all four cameras at a whopping 12,800 (that's 3 full stops above both the Canon and Nikon, 2 stops above the Sony)!  Also has HD video capability, and slightly higher resolution at 12 megapixels (all the others are 10).  It also one of the few cameras that still runs on AA batteries, which can sometimes be an advantage since they are available everywhere.  At $460 its in the middle of the pack on price.  The only disadvantage is doesn't appear to be self-cleaning like the other 3 cameras.

So what's my verdict?  If you don't have a brand preference, I would pick the Pentax K-x.  Its the most bang for your buck and has specs and features you'd expect in a much more expensive camera.  

However, if you really want to have unlimited room to grow, I might go Nikon or Canon.  The fact is they are the gold standards of the camera industry, and you know you are getting a quality product backed by decades of experience.  They have much larger lineups of cameras, lenses and accessories than either Sony or Pentax, and you're simply never going to outgrow their product lines.

If price is a big deal, and your wife or husband is sweating you about how much cash you're trying to blow on camera gear, pick up the Sony.  Its the most value-oriented choice, and you're not going to be missing out on anything, its still a fantastic camera.

Aaaaand DONE!  Is that enough info for you?  So now, go buy your camera, you kinda need one of those to learn photography!

Metering Mode pt. 2 - Center-Weighted and Spot Metering

OK, so yeah, I've been gone for a month.  Not out-of-town gone, more the wife-had-surgery-work-went-bananas-at-the-same-time type of gone.  But regardless, I'm back, and we need to continue our photo education, so lets get to it.

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In the last post we talked about matrix metering, which involves some pretty complex decision making on the part of the camera.  Now let's get into center-weighted and spot metering modes, which are much simpler and more predictable.

Center-weighted metering behaves the most like the classic "average luminance" metering we discussed in the first post on metering.  There is one difference however.  As implied by the name, center-weighted metering cares more about the center of the frame than the edges.  When I say the center, I mean a circle or oval taking up about 50-70% of the frame (the actual area being measured depends on your camera).  Center-weighted metering will suggest exposure settings that render this circle / oval area a medium gray, with some minor consideration given to very dark or very bright areas at the periphery of the frame.

There are two great thing about center-weighted metering:

1. It's predictable.
2. It prioritizes the center of the frame (where your subject tends to be located a lot of the time).

Center-weighted metering is good in situations where the center of the frame needs to be properly exposed and the edges don't matter.  For example, a portrait where the sun is setting right behind your subject, or a still-life shot of a leaf, sitting in a pool of light on the otherwise dark forest floor.  Makes sense right?

Now let's move on to spot metering.  Spot metering only measures a tiny portion of the frame (normally 2-5% of the total image area).  This spot is always in the center of the frame, although in some newer professional cameras it is possible to move the spot around.  Spot metering will suggest exposure settings that will make the object inside the spot appear a perfect 50% medium gray.

The two advantages of spot metering are:

1. It's almost perfectly predictable.
2. You can meter very small areas of the frame separately from each other.

Spot metering is good if you need a very precise meter reading for one tiny portion of the image and want to ignore everything else.  Now remember, when you spot meter an object it's going to give you exposure values that will make that object medium gray.  If you're spot metering a light-toned object you'll have to overexpose compared to the meter reading.  If you're spot metering a dark object, you'll need to underexpose it somewhat.  Spot metering also works great with auto-exposure lock, another feature we will come to shortly.

Metering Mode pt. 1 - Matrix Metering

OK, let's talk some more about metering. In the first post on metering, we oversimplified things a little too much. Don't worry, it's not really going to get more complex, but we need to refine the details a little.

We started with the understanding that your in-camera meter uses "average luminance" (i.e. brightness) to determine what exposure settings to use. That meant the camera's meter measured the total amount of light coming in through the lens, and assumed this light was spread perfectly evenly throughout the frame. The meter then suggested exposure settings that would make this average amount of light come out a medium gray tone in the final image.

This IS how light meters started out, however photography has come a long way and we now have more than one "metering mode" that controls how the meter behaves. There are basically three standard metering modes: matrix, center-weighted and spot.

"Matrix metering" is the smart(-ish) metering mode that is standard for almost all modern cameras. I'm going to use "matrix metering" in this post, but this is technically the Nikon term. I believe Canon calls it "evaluative metering" and the generic may be "zone metering", but I learned on Nikons and therefore I'm rolling with "matrix".

Matrix metering divides the frame into several different "zones" and measures the light in each zone separately. It uses this information to try and "guess" what kind of scene you are shooting and make exposure recommendations that would be best for this type of scene. Before this week that's basically all I knew about it, but thanks to Ken Rockwell's website (google him) I learned a bit more.

Let's use our old example of a snowy pasture to show how matrix metering works. Let's say our composition consists mostly of a snowy field, with a couple clumps of dark trees on the left side and the bright sun in the upper-right corner of the frame. Matrix metering is smart enough to know that there is nothing brighter than the sun that it can reasonably expect to run into. So when it measures something as bright as the sun in the frame (i.e. which is always the sun itself) it pays special attention to that. Matrix metering also knows that direct sunlight is very consistent and always produces the same amount of light. So now, matrix metering will pick exposure values that are suitable for subjects lit directly by the sun, and we will get realistic tones in our image that match what we see with our eye. The sun will be pure white, the snow will be a pretty bright white, and the dark trees will be black. Good job matrix metering!

Matrix metering has a lot of other logic included that helps it make good decisions. It is good at measuring the brightest and darkest areas of an image and trying to distribute these tones within the dynamic range of the camera. This means it tried to keep the brightest areas bright, and the darkest areas dark and strike a compromise somewhere in the middle. Here's a good example of it doing that:

See how it picked exposure settings that kept the dark areas from being pure black and the white areas from being pure white? It did a decent job of retaining detail in both these areas, and this looks reasonably like the scene did in real life (I know, a picture of the leg of my couch, how interesting).

That being said, as smart as matrix metering is, it is definitely not perfect and can be fooled. Let's go back to the snowy pasture example and pretend it is an overcast day instead. The meter is not going to see anything bright or dark enough to give it a good idea of what you are shooting. So it goes back to being a normal light meter. Most of the frame is snow, so it's going to make that medium toned (i.e. gray). If there are enough dark trees in the frame, its going to take them in consideration too and maybe pick slightly brighter exposure settings. In this case the snow may be a slightly lighter gray, but still not the white we are looking for. Sorry matrix metering, we know you tried.

Final thought: matrix metering is a good way to go most of the time for decent pictures. Its fairly smart and makes a lot of reasonable decisions. The problem is it still a machine, not a mind reader, and doesn't know your creative intent. Another problem is that it is not very predictable. If you are trying to over or underexpose something, its hard to know what the meter is already doing. Maybe it knows to overexpose the scene already (like the sunny snow day), or maybe it is hopelessly lost and shooting for a compromise (the cloudy snow day). If you are making your own adjustments, you have to guess how the meter already feels about this scene, which can be a mess.

That's the complex world of matrix metering, now let's move on to center-weighted and spot metering, which are much simpler!

A Quick Word About the Zone System

This is an afterthought to the last post on dynamic range, but let's take a quick look at the Zone System. This is something Ansel Adams and his buddy Fred Archer put together in the 1940's, originally designed for black and white film.

Basically they created their own 10-stop scale of tones from pure white to pure black (11 tones in all). This scale was supposed to represent the full range of black and white film and the paper it was ultimately printed on. Just to make things confusing, they labeled these zone "0" (zero) through "X" (roman numeral 10).

The idea was, the meter will always give you a reading for the middle gray tone "V" (5). Want to render whatever you just metered as zone "VII" (7, a light tone)? Overexpose by 2 stops. Want something to be zone "II" (2, a very dark tone), underexpose by 3 stops. Got it?

So why aren't we using the Zone System to talk about exposure? Well, first of all this scale represents the theoretical dynamic range of black and white sheet film, but all I care about the actual dynamic range of the digital camera I am using.

Second, I hate the numbering system. Roman numerals suck and are irritating to use. Also this doesn't match up to anything you see in modern cameras. Do I ever see a "VIII" or "IX" on my in-camera meter? No, I see "-2, -1, 0, +1, +2". Zero is metered value, not "V". Negative numbers are underexposure (darker), positive numbers are overexposure (brighter). That's pretty intuitive, right?

So that's why I more or less skipped the Zone System. This may make old school photography teachers want to cry, but I'm trying not to waste your life here. If you're shooting black and white sheet film and hand developing and printing it, learn the Zone System in depth, there are tons of books on it. If you're the other 99.99% of the population you can safely ignore it.

Tonality & Dynamic Range

In the last post, we discussed how your in-camera meter uses the average "luminance" (a.k.a. brightness) of a scene to suggest correct exposure settings. The problem we ran into was that the meter wants to treat everything like its medium gray. Its operating on the assumption that the light and dark areas in your scene fall neatly on either side of this "average luminance" and that this will be a good predictor for how you want your image exposed. However, not all scenes are average! The meter struggles with subjects that are supposed to be very light (snow) or very dark (a black cat). This is where we begin our discussion of tone.

Let's start by saying that your digital camera records two different types of information about light: luminance (amount of light) and color (you know what color is!). The camera takes the amount of light it receives (luminance) and renders this into different tones, that is, light or dark areas on the final image. Pure white, light gray, medium gray, dark gray, pure black, these are all examples of tones. We are ignoring color entirely here, for this post it doesn't matter if the medium gray was a medium red, green or blue, we're just talking about how light or dark this area is.

Now let's get down to brass tacks. If you are photographing something dominated by light tones (say a snowy pasture), you now know that the meter will suggest exposure values to make the scene medium toned (i.e. gray, dingy looking snow). Since we want bright white snow, we also know we have to overexpose this image compared to the meter's recommendation, but the question is, how much? 1 stop? 2? How do you know?

This is where dynamic range comes into the picture. Look at the picture below.

I took this series of test shots with my Nikon D200 for this post, to show the range of tones actually recorded by my camera. Slightly to right of center, you see the swatch of gray that says "0.0, 55%, metered value"? This is a piece of white typing paper shot at exactly the exposure settings recommended by the meter. It ended up being 55% gray (one would expect 50% gray, but hey, this is a real world test). This is a medium tone, which is what we should expect now that we know how the meter works.

In all of the swatches to the right, I overexposed according to the meter, first by one stop (+1.0), then two (+2.0), then three (+3.0). One stop overexposed brought me to 75% gray (a light tone), two stops produced 95% gray (almost white), and three stops overexposure gave me a featureless pure white.

Going to the left, one stop underexposure gave me a 35% gray, a fairly dark tone. Two stops underexposure created a 20% gray (even darker), three stops under was a 12% gray (pretty damn dark), four stops under equalled 5% gray (almost black) and five stops under exposed took me to 0% gray (pure black). By the way, I should probably be saying "0% lightness" instead of "0% gray", but you get the idea.

Did you notice something? It took only three stops OVER exposure to get to pure white, but five stops of UNDER exposure to get to pure black. Interesting huh? This range, from pure white to pure black, is called the "full range" of this camera, which happens to be approximately 9 full stops. On the other hand, the range from almost pure white to almost pure black (equivalent to 5% and 95% on the illustration above) is called the "dynamic range", which is approximately 7 full stops.

The important thing I learned from the above experiment was how much brighter or darker my camera makes an image with a one, two, or three stop adjustment from the metered value! We also learned that this is NOT linear, which is very useful. Intuitively you'd expect there to be a certain percent change in brightness for each full stop, say 20% brighter per stop. Go ahead and throw that idea out the window. Exposure isn't linear, its supposed to be logarithmic, but even that doesn't perfectly correspond to how a real camera works in a real situation. The important thing to know is how YOUR camera responds to changes in exposure, so you can create the kind of images YOU want!

To wrap things up, let's go back to our snowy pasture example. More specifically, let's say we are photographing one lonely sapling sticking up out of the snow. Almost the entire frame is filled with white snow, the thin black stick of the sapling is hardly contributing to the meter reading at all. So how much should I overexpose this? It depends. If I want a white, gleaming snow with no detail probably 2 stops, maybe even 1/3 or 2/3 stops higher than that. What if I want to really capture the texture in the snow itself but still render it a light tone? I'd probably go 1 stop over, or 1 and 1/3.

Ultimately I'd make some educated guesses, look at the photos on the back of the camera and at home on my monitor, and try to remember how I would have done it differently the next time I'm out shooting! The point is, it takes practice to learn how your camera renders different tones, and also how your meter evaluates different scenes. This post should give you a good starting point of what to expect so you don't have to feel overwhelmed. In the end your knowledge will always be fine tuned by experience, so go out and start experimenting!

Metering

In the previous post, I talked about how your camera will make change your exposure settings for you in certain exposure modes. So how does it do that? How does it know how much light is present in the scene you are photographing?

The answer is: by using a light meter. A light meter is a device that (like its name implies) measures light. There are two basic types of light meters, "incident" and "reflective".

We'll start with incident meters because we won't spend much time on them. Incident meters are handheld devices with a white globe on top (example picture below). If you've ever watched part of a fashion shoot on TV, you may have seen one of the photographer's assistants sticking this in front of the model's face repeatedly as they adjust the lights. This is because incident meters measure the light that falls on them directly, so they have to be placed where the subject is to get a useful reading. This works well for portraits, product shots, and anything where the subject is close at hand. Incident meters are not practical for landscape shots, sports, or anything where the subject is far away or moving.

To use an incident meter, you set the desired ISO on the meter, place it in front of the subject (white globe facing the camera), and press the button to make it measure the incident light. The meter then gives you a f/stop and shutter speed setting that should result in a correctly exposed photograph. The meter will also have a wheel where you can change either the aperture or shutter speed setting it suggested. When you do this, it will automatically adjust the setting you didn't choose in the opposite direction so the exposure will still be correct. This is useful when you need to use a certain aperture or shutter speed for creative reasons.

Now on to reflective metering. Reflective light meters measure the light that is being reflected off objects in the scene and enters the camera. While there are handheld reflective light meters, almost all modern cameras have built in reflective light meters. This type of built-in meter is often referred to as TTL metering (through-the-lens), since the meter actually measures the light that is entering the lens of the camera. Learning how to use this in-camera meter is absolutely essential to taking well exposed photographs.

So how does your camera's meter work?

Well, in its simplest form, the meter uses "average luminance". This just means it measures the total amount of light coming in the lens, and assumes that this light is evenly distributed over the entire frame. It then determines the exposure settings that would make this average light level come out a medium gray (more or less half-way in between pure black and pure white). The camera designers know that the the world isn't medium gray, but they are shooting for the middle ground to get you a decent exposure.

So how do you use your in-camera meter? If you are in Manual exposure mode, you should see a bar like this:

Ok, this is the entire control panel from the top of my D200, but see the bar in the middle, with the plus on the left, zero in the middle and minus on the right? That's what we're talking about. This should be visible somewhere on one of your camera's control panels, in the manual exposure mode if not others.

What this bar tells you is how over or under-exposed the meter thinks your image will be at your current exposure settings. In the picture above, the bigger hash marks stand for whole stops, the smaller marks for 1/3 stops. The "plus" side of the meter is overexposure (too bright), the "minus" side is underexposure (too dark). So at 125th of a second, f/5.6 and ISO 800 (ISO not shown here), the meter thinks whatever my camera was pointed at (the dining room wall?) would be 1 and 2/3 stops underexposed. Ok here comes the important part so pay attention:

The meter thinks you want everything (on average) to be medium gray. But what if your subject is very dark or very bright and you want to keep it that way? If you take a landscape of a bright snow scene, you want the snow to be white instead of dingy gray, right? If you take a picture of your black cat on your black leather couch, you don't want a gray cat on a gray couch either.

So how do you deal with that? If you know you want your scene to appear light-toned (bright), pick exposure settings that the meter thinks are over-exposed (towards the plus sign). If you want to make your scene dark, select exposure settings that the meter thinks are under-exposed (towards the minus sign).

THAT'S IT! This is something a lot of photographers never really get a handle on, so learn it now! There's some practice involved to get this figured out, so go experiment!

Exposure Mode

So far in this blog we've established that only three camera settings control how bright or dark a photograph is: aperture, shutter speed, and sensitivity. Absolutely every time you take a picture, all three of these exposure settings are set to a certain value. So the question is: if you haven't been setting your exposure settings, who has?

The short answer is your camera. A better answer is, it depends on your "exposure mode".

Exposure mode is the setting that determines how your exposure settings are controlled. Most cameras that have adjustable exposure settings also have several exposure modes to choose between, depending on the situation you are shooting in. We'll cover the big four in this post: Manual, Aperture Priority, Shutter Priority, and Program.

So far in this blog we have been assuming you are using "manual" exposure mode. In manual exposure mode you must set your aperture, shutter speed and ISO yourself using the switches, dials or menus on your camera. If you don't change it, it doesn't change. The big advantage of manual exposure mode is you have total control over your exposure. The bad news is every time the light changes, you'll need to adjust your exposure settings. Sun goes behind a cloud? Change. Sun comes back out? Change. Want to photograph something in the shade instead? Change. And changing settings takes time. Sometimes you may miss the moment fiddling with the camera, or forget to change your settings and get a poorly exposed image. That being said, manual exposure mode is very powerful because you are calling all the shots and have total creative control. A lot of professionals and artists only shoot in manual mode for this reason. Manual exposure mode is available on all professional cameras and on many higher quality "point-and-shoot" (consumer) cameras.  It is normally designated with a capital "M".

Now let's talk about Aperture Priority. With this exposure mode, you are only responsible for one exposure setting: aperture. You get to pick the aperture and the camera sets your other exposure settings (to be more accurate, most cameras will only compensate by changing your shutter speed and won't alter your sensitivity [ISO] setting). Aperture priority is very useful if you're concerned about controlling depth of field for an image and don't have enough time (or energy) to deal with manual mode. If you have Aperture Priority exposure mode available on your camera, it will probably be denoted with an "A" or "Av" symbol.

Shutter Priority is just what it sounds like and also the opposite of aperture priority. You pick the shutter speed, the camera adjusts the aperture. Like with aperture priority, most cameras do not adjust your ISO while in shutter priority mode. Shutter priority is great when motion is a big part of the image and you either want to blur or freeze the moving parts of the image, but aren't particularly worried about depth of field. Shutter priority is normally represented with an "S" or "Tv" (for "time value" if you were wondering).

The last exposure mode I'll talk about, Program Mode, perhaps should have been called Sensitivity Priority. In program mode, you set only the ISO and the camera adjusts the aperture and shutter speed as needed. This is a good choice when you need to concentrate on your timing to capture a moment and neither depth of field or motion blur are incredibly important. Program mode is generally represented with a "P". Also it is worth mentioning that some cameras adjust ALL your exposure settings in Program Mode, including your ISO. This is sometimes billed as "intelligent Program Mode" or something similar.

Ok, so what if you have other modes on your camera, and maybe don't even have any of the ones I mentioned above? Isn't "portrait" (perhaps a silhouette symbol) or "macro" (the flower symbol) or "landscape" (maybe a mountain symbol) an exposure mode? Well kinda. These are really "scene modes", similar to an "intelligent Program Mode" where the camera sets all of your exposure settings for you. But these scene modes also tend to control other camera functions such as focusing, metering and tonal rendering (don't worry, we'll cover those concepts later). Is this a bad thing? Not necessarily, but for the purposes of controlling your exposure settings, all of these function like an intelligent Program Mode where all the exposure settings are adjusted for you. If you aren't sure which exposure modes are available on your camera or exactly how they function, be sure to check your camera manual.

Ok, now we know how to control who is making your exposure setting decisions and why we might want to change that depending on the situation we're shooting in. Next we'll talk about how to choose the right exposure settings depending on the amount of light in the scene using a very important concept: "metering".