Overriding Autoexposure Results with Exposure Compensation

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When you set your camera to the P, Tv, Av, or A-DEP exposure modes, you can enjoy the benefits of autoexposure support but still retain control over the final, overall exposure. If you think that the image the camera produced is too dark or too light, you can use a feature known as exposure compensation, which is sometimes also called EV compensation. (The EV stands for exposure value.)

Whatever you call it, this feature enables you to tell the camera to produce a darker or lighter exposure than what its autoexposure mechanism thinks is appropriate. Best of all, this feature is probably one of the easiest on the whole camera to understand. Here's all there is to it:

i Exposure compensation settings are stated in terms of EV values, as in +2.0 EV. Possible values range from +2.0 EV to -2.0 EV.

i A setting of EV 0.0 results in no exposure adjustment.

i For a brighter image, you raise the EV value. The higher you go, the brighter the image becomes.

i For a darker image, you lower the EV value. The picture becomes progressively darker with each step down the EV scale.

Each full number on the EV scale represents an exposure shift of one full stop. In plain English, that means that if you change the exposure compensation setting from EV 0.0 to EV -1.0, the camera adjusts either the aperture or shutter speed to allow half as much light into the camera as you would get at the current setting. If you instead raise the value to EV +1.0, the settings are adjusted to double the light.

By default, the exposure is adjusted in 1/3 stop increments. In other words, you can shift from EV 0.0 to EV +0.3, +0.7, +1.0, and so on. But you can change the adjustment to 1/2-stop increments if you want to shift the exposure in larger jumps — from EV 0.0 to EV +0.5, +1.0, and so on. To do so, display Setup Menu 2, highlight Custom Functions, and press Set. Then select Custom Function 6, press Set, and press the up or down cross key to change the setting. Press Set again to lock in the new setting. If you make this change, the meter will appear slightly different in the Camera Settings display than you see it in this book. (There will be only one intermediate notch between each number on the meter instead of the usual two.) The viewfinder meter does not change, but the exposure indicator bar appears as a double-line if you set the exposure compensation value to a half-step value (+0.5, +1.5, and so on).

Exposure compensation is especially helpful when your subject and background are significantly different in brightness. As an example, take a look at the first image in Figure 5-17. Because of the very bright sky in the background, the camera chose an exposure that left the palm tree too dark. So I just amped the exposure compensation setting to EV +1.0, which produced the brighter exposure on the right.

Figure 5-17: For a brighter exposure than the autoexposure mechanism chooses, dial in a positive exposure compensation value.

Another possible way to cope with this kind of background/subject brightness variation is to adjust the exposure metering mode, as discussed earlier in this chapter. I took the images in Figure 5-17 in Evaluative mode, for example, which meters exposure on the entire frame. Switching to Partial or Center-Weighted Average metering might have done the trick, but frankly, I find it easier to use exposure compensation than to fool with metering mode adjustments in most situations.

Some photographers use a slightly lower exposure compensation value — say, minus 0.3 — for all their shots. The thinking is that while this setting may underexpose some images, resulting in a little necessary retouching work later, it helps protect against blown highlights, which are usually not easy to repair.

Whatever your reason for adjusting the exposure compensation setting, you can get the job done as follows:

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Digital Camera and Digital Photography

Digital Camera and Digital Photography

Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.

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