Exposure Illustated

We've talked a lot about exposure, now let's look at some pictures.

In the center of this composite is a more-or-less correctly exposed image. Based on the amount of light in our dining room, I ended up with f/2.8 (aperture), 1/30th of a second (shutter speed) and ISO 800 as my exposure settings to give this result.

Now look at the row of dark images on the left side. All three of these images are one full stop darker than the center image. To get the upper left image, all I did is increase the shutter speed to 1/60th of a second. In the middle-left image, I decreased the aperture to f/4 instead. In the bottom-left image I lowered the ISO to 400 instead.

The point is there are 3 equally valid ways to make an image darker:

1. Increase the shutter speed.
2. Decrease the aperture (remember, this means a higher f-number)
3. Decrease the ISO.

Now look at the right row of images above. These are all one full stop brighter than the center image. In the upper right image, I decreased the shutter speed to 1/15th. For the middle-right image I increased the aperture to f/2 instead. For the bottom-right image, I increased the ISO to 1600.

So these are your three options for making an image brighter:

1. Decrease the shutter speed.
2. Increase the aperture (lower f-number)
3. Increase the ISO.

So if there are always three ways to make an image brighter or darker, how do you choose which exposure setting to change? We'll cover that next.