June 28, 2010

Getting the Exposure You Want, Part I


After sharp focus, good exposure is the next characteristic we want for our photographs. Most of the time, the camera's automatic exposure gives us a photo that's not too bright and not too dark. But sometimes the camera is wrong when it comes to exposure. How can we make the camera take a picture with a different brightness?

Exposure Lock
One way you can get a different exposure is very low tech and works on every camera in nearly every shooting mode (except Manual exposure mode). This is called exposure lock. When you press the shutter button half-way down to prepare to take a photo, the camera is making adjustments to a variety of automatic settings. One of these is exposure. The camera determines the exposure (or brightness) of the image based on what you have included in the frame.

For example, the picture at the beginning of this article is made up of half mountains and half sky with cloud. When I made this picture, I pointed the camera so that the scene was evenly divided between foreground hills and sky. The camera based its exposure on this and produced the photo.

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If I point the camera at a slightly different part of the scene, I can create a very different exposure. In the photo below, I tilted the camera up so that only the sky with cloud was visible. Then I pressed the shutter button half-way down to lock the exposure. Still holding the shutter button half-way down, I reframed the scene to include the mountains. Then I actually took the picture.

Darker Exposure of Sky

The effect of pointing the camera at the sky and locking in the exposure gives me a photograph that is a better version of the cloud than I had with the first picture.

What if I'm interested in a better exposure of the foreground instead of the sky? In the first picture below, I pointed the camera up at the overcast sky and pressed the shutter button half-way to lock the exposure. Then, keeping my finger on the shutter button, I  reframed the scene to include trees and river. Then I clicked the picture. The result is a good exposure for the sky, but the foreground is too dark.

Dark Exposure of Sky

In this situation, the sky is not very interesting. So having a darker exposure of it doesn't help my photo. Let's try again. This time I pointed my camera down at the trees and water, and pressed the shutter button half-way to lock the exposure. Then I reframed the picture to include the top of the mountain and pressed the shutter button down to make the image. Now the camera has made a brighter exposure for the more interesting part of the scene, the trees and river.

 Brighter Exposure of Trees
 
 From these examples, you can see that where you point the camera has an effect on the exposure. How do you know where to aim the lens for the best exposure? Ask yourself, what is the most important part of the scene? 

If the most important part is the sky, point the camera at the sky and lock in the exposure by pressing the shutter button half-way. Then adjust the composition if needed and press the button to take the photo. If the most important part of the scene is the foreground, point the camera at that part of the scene and lock in the exposure with the shutter button. Adjust the framing if you want to and then take the photo.

These examples demonstrate tilting the camera up or down to change the exposure. But you can also turn the camera left or right to achieve a similar effect. Just remember to point the camera at the part of the picture where the exposure is most important. And remember to take a picture normally (without exposure lock) for comparison.

You can see that exposure lock is a very easy way to change how light or dark your photo is. But you don't have any control over how much lighter or darker the picture is. The camera is still deciding that for you. If you want to tell the camera how much brighter or darker your picture should be, you need to use a different technique. And that's the subject of the next blog post! Stay tuned!