Saturday, February 07, 2009

Tricky Lighting Situations,Use Exposure Compensation

There are several solutions to these kinds of problems, and you can experiment to see which
works best for you in various situations. Here are some ways you can correct your exposures
when you see a problem in the viewfinder:
■ Use exposure compensation Use the exposure compensation control, sometimes
abbreviated as “EV” or labeled with a +/– symbol, to intentionally under- or overexpose
your pictures beyond what the camera’s exposure sensor recommends.
■ Switch metering modes Use a different kind of exposure meter to account for highcontrast
■ Use exposure lock Lock your exposure on a different part of the image, and then
recompose the picture and shoot.
To see how to use each of these exposure techniques, keep reading.

Use Exposure Compensation
Most digital cameras come equipped with an exposure compensation control, usually referred to
as the Exposure Value (EV) adjustment. The EV control, which typically looks like a +/– symbol.
like in the following illustration, allows you to use the camera’s recommended automatic
exposure setting but then adjust that value up or down based on factors that you’re aware of
but that the camera may not be smart enough to see. Each Exposure Value corresponds to changing the exposure by one stop, such as going from 1/60 to 1/30 (this is a change of +1 EV since it doubles the exposure) or 1/15 to 1/30 (this is –1 EV since it reduces the exposure by half).

Take example below.In the original picture (on the left), the dark stuffed penguin has confused the camera, making it think the scene was properly exposed when, in fact, it is horribly overexposed. The background and the other animal are nearly invisible as a result.

The EV control lets you use your own judgment about exposure values instead
of relying exclusively on the camera’s meter.

When the camera is set to underexpose the scene by one EV (one stop), however, the scene is much better exposed. The image was saved, as you can see on the right side of Figure.

To use the EV control on your camera, do this:
1. Size up the scene you want to shoot. Decide if it calls for over- or underexposure.
2. If you need to add light to a scene to properly expose it, add exposure by setting the EV
control to +1 (some cameras also let you vary the exposure by a fraction of a stop,
such as .3 or .7). If instead you need to underexpose the scene, set the EV control to
–1. Of course, since you can see the results right away in the camera’s digital viewfinder,
feel free to add or remove EVs until the picture looks about right. Here’s a typical
digicam display set to EV +2:
3. Take the picture and review the picture in the LCD display. If you don’t like the result,
adjust the EV and shoot it again.
Most cameras allow you to adjust exposure by up to three EVs, either positive (overexposed)
or negative (underexposed).

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