Saturday, March 14, 2009

Use Exposure Lock

Not all cameras offer exposure lock, but those that do are a godsend. Exposure lock is usually
achieved by applying slight pressure to the shutter release—not enough to activate the shutter
and take the picture, but enough that you feel the button move and the camera itself respond.
Here’s what happens when you take a picture:
1. Apply slight pressure to the shutter release button.
2. As you feel it depress slightly, the camera’s autofocus lens locks the current subject into
sharp focus.
3. At the same time, the camera’s exposure meter measures the light and locks in an
4. Apply more pressure to the shutter release to press it in all the way. The camera then
takes the picture and saves it to memory.
@The spot meter is a great tool for reading the proper exposure in one precise
point of the image.

The magic of exposure lock is that as long as you continue applying pressure to the exposure
lock control, the camera will use that locked-in exposure information regardless of where you
later point the camera. You can lock in exposure information for the sky and then point the
camera at your feet and snap the shutter release all the way. You’ll take a picture of your feet
using the sky’s exposure data. You probably wouldn’t want to do that since the result will be
totally underexposed, but it gives you an idea of the potential.
Some digital cameras have a separate focus lock and exposure lock control; you should
check your camera’s manual for details. In such cameras, there’s a separate button somewhere on the camera (usually where your thumb would fall on the right side of the camera body), possibly labeled AEL (short for auto-exposure lock). To use it, point the camera where you want to lock exposure settings and press firmly down on the AEL button. Continue to hold the button down while you recompose the photo, and then take the picture by pressing the shutter release.
Exposure lock is a great tool for telling the camera that you’d like to take a picture with the exposure data from one specific part of the scene.
Instead of taking a picture that averages all the light values to give you an average picture,
here’s what you should do, step by step:
1. Frame the scene in your viewfinder so you know what you want to photograph.
2. Before actually taking the picture, point the camera up into the sky. Include the brightest
part of the sky that doesn’t also include the sun—that might be overkill. Sounds like
guesswork? It is, a little. This is art, not science. You can take the picture, see if you like
the result, and reshoot as necessary.
3. Press the shutter release partway to lock in the exposure information. You should sense
that the camera has also locked the focus at the same time.
4. Recompose your picture. When you’re happy with the scene in the viewfinder, press the
shutter release all the way to take the picture.
Obviously, you could also choose the spot meter (if your camera has one) and lock the
exposure with that instead of the default center-weighted or matrix meter in that you used
in steps 2 and 3. It’s up to you. This is a real challenge for most cameras, since the subject is a wolf sunning itself in an isolated patch of light. A center-weighted camera would probably average the light in the darker surrounding areas and determine that it needed to select a fairly wide-open aperture to add light to the scene. But that would wash out the poor little wolf. Instead, the best solution is to select the spot meter, frame the wolf carefully, and press the shutter release partially to lock in exposure on the bright subject. Then reframe the
picture and shoot.
As you become more confident with your ability to visualize compositions and exposures,
you can try different things to get the desired effect.

Bracket for Success
A common photographic technique that you might occasionally want to try is called
bracketing. Bracketing your photos is simply the process of taking several pictures, each with
a slightly different exposure, so at least one of them will look the way you want. When you’re
done, review all the bracketed pictures on your PC and discard the ones you don’t like.
Suppose you’re trying to take a silhouette, for instance. You need to make sure the subject is sufficiently underexposed
that it appears totally dark, with no detail. How can you do that? There are two common
methods for bracketing:
■ Use your camera’s auto-bracketing feature Many digital cameras have
something called auto-bracketing—turn it on, and it’ll take three pictures in quick
succession when you press the shutter release. One will be the “proper” exposure,
but it’ll also capture slightly over- and underexposed images for insurance.
■ Use exposure compensation Take one picture normally, and then take additional
photos after changing the EV dial to under- and overexpose. You should start with
exposure variations of a half-stop or full-stop (1/2 or 1 on the display), since more
than a full stop of exposure compensation can be dramatic.

When to Take Control
As I mentioned at the outset, you may often be perfectly satisfied with the results you can get
from the automatic exposure controls in your camera. But there will be times when you can do
better on your own. Keep your eyes peeled for situations like those described next.
Very Bright Sunlight
Very bright sun can overwhelm your camera, especially if the scene is filled with brightly
colored clothing, reflective surfaces, or other tricky subjects. You can reduce the exposure for
better exposure. Underexpose the scene by EV –1 for starters and see if that helps.
Backlit Subjects.If you are taking a picture of someone or something and the sun is behind the subject, you’re usually in trouble—the bright background will cause the camera to underexpose the scene. That means the subject itself will look like it’s in shadow. You’ll get this if you follow the old (and very wrong) rule to put the sun behind the person you’re photographing. The best way to shoot an outdoor portrait is to put the sun over your shoulder. Nonetheless, if you find the sun behind your subject, overexpose the scene, such as with an EV +1. Of course, this may overexpose the background, but that’s probably okay—your priority is properly exposing the subject in the foreground.
Low Light
In low light, such as at night, indoors, or under thick cloud cover, you can often get better results
by overexposing the scene slightly, such as with an EV +1. Vary the EV level depending on how
dark the scene actually is.

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