Friday, June 6, 2014

Pluses and Minuses: Exposure Compensation (Advanced Photography Part 1)

Advanced Photography Part 1: Exposure Compensation

So, you've read all of my Photography Basics series, but want more? Well, I'm here to help. This week's topic will be exposure compensation.

What is exposure compensation?
Exposure compensation is a feature you should find on most "pro-sumer" and advanced digital and film cameras. It allows you to make manual adjustments to the exposure time, separate from the aperture and shutter speed adjustments.

The button usually looks something like this:

Exposure compensation will allow you to either add or subtract time from an exposure. Usually, the increments are -0.3, -0.7, -1, 0, +0.3, +.07, +1, etc. The negative values shorten the exposure time (decrease light, increase shutter speed), while the positive values will lengthen the exposure time (more light, slower shutter). Make sense?

Okay, so when would I want to use exposure compensation?

Advanced digital cameras have complicated computers inside of them that calculate the exposure for us, eliminating the need for manual calculations for each shot. However, sometimes these computers make errors - and exposure compensation can be used to correct them. It also can be used to achieve different artistic effects in images.

White or Black Subjects

Many automatic exposure calculators have difficulty with white or black subjects, such as these egret chicks. All-white subjects, particularly against darker backgrounds, are often overexposed by automatic readings. This means you may end up with a completely white subject - not desirable. In this situation, you will want to decrease the total exposure - reducing the light and allowing detail to be rendered properly in your subject. You can use exposure compensation to do this. You will probably want to take several shots - a few with no compensation, a few with -0.3, some with -0.7, etc, depending on how bright it is. This is called bracketing your exposure, and some cameras can even be set to do it automatically. 

Sloth Bears

For very dark or black subjects, the opposite tends to be true. In-camera exposure calculators will tend to underexpose the image, resulting in an entirely black subject. Increase your exposure (positive exposure compensation) to avoid this problem.


Backlit Subjects

Backlit subjects suffer from being a relatively dark object in a relatively bright field. The exposure meter will be fooled by this, recognizing the overwhelmingly bright scene instead of your intended subject. This can produce a very underexposed subject. To remedy this, try bracketing your exposure upwards - ie, positive exposure compensation. Alternatively, if you want to silhouette your subject against a brilliant background (perhaps a sunset?), bracketing down (negative exposure compensation) will help you.

Strongly Illuminated Subjects

Subjects with very bright lighting may also benefit from bracketing down of your exposure. Taking multiple shots with different exposure settings is the key to achieving the perfect exposure in difficult lighting.

So, have you ever used the exposure compensation setting on your camera? Do you use automatic bracketing? Let me know!

Did you see last week's post on why you should always bring your camera?

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