Tuesday, July 26, 2011

Using Exposure Compensation

Last month we talked about understanding in-camera metering. We mentioned using exposure compensation, but wanted to expand on the topic by covering not only what it is, but explaining what it does and how to use it.


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In a perfect world, anyone could take a picture and get wonderful results every time. Unfortunately, most people will confirm that our world is not perfect. That being said, we photographers will sometimes need to override the automatic settings on our cameras in order to get the desired results - properly exposed images. Let's consider a few examples that most of us have encountered, and what we can do to make things better.

a digital meter scale

For those of you who get to experience the cold winter weather, I'm sure that you've experienced those pictures in the snow where the subject is darker than it should be, and if you're shooting in color, the snow may have a light blue cast to it. Or, for those of you that like to take pictures at the beach on a bright sunny day, how about those pictures taken with the water behind the subject, or a portrait with a beautiful sunset in the background. Most likely, the subject will be under exposed and darker than you'd like. Keep in mind, most cameras with automatic settings will try to average out the exposure between the subject and the background, and in extreme contrast situations like mentioned above, the camera can get fooled. So what can you do?

an exposure compensation button

There is a setting on most SLR cameras called Exposure Compensation. This is a setting that will allow your camera to set its exposure, and then allows you to intentionally override the exposure by up to 3 f-stops in either direction (under or over expose) to get the desired results. With many of the early film cameras, this was usually a dial on the top of the camera that went from -3 to +3. With some of the newer SLR cameras, it was changed to a button.

an exposure compensation dial (on a newer p&s digital)

If your camera doesn't have an "Exposure Compensation" setting, you can still correct for this. If your camera has a manual override, you can read what the camera would be set on (if left on automatic), then change to a manual setting that is 1 or 2 stops different. If the camera only has an automatic setting (no manual override), you can manually change the ISO (ASA) setting to fool the camera into thinking that it has a more sensitive "film" in it. For example, if you're shooting ISO 100 film, change the setting to ISO 200 and you're going to underexpose your image by 1 stop. IF you set it on ISO 400, you'll be underexposing by 2 stops. *REMEMBER TO CHANGE IT BACK WHEN YOU'RE DONE*. So how do you know where to set the override? That, my friends, comes with knowledge and experience. You can acquire the experience by simply going out and trying these ideas on your own. Keep a note pad in your camera bag so that you can make notes of the settings that you used on each picture, so that you can understand and then duplicate what worked on future images. Many digital cameras will allow you to display this data after the picture has been taken by looking at the EXIF data.

A good example of why you would want to underexpose and image would be if you were taking a picture of a full moon on a clear night. If you keep your camera on automatic, you'll see a bright light in the sky, but no detail in the moon. By underexposing by 2 or 3 stops, you'll see the detail and might just capture the best moon photo you've ever taken.

Another setting on your camera that was designed to help correct for these issues is called the Exposure Lock. This is typically a button that you push to lock in the exposure that the cameras light meter had taken. In order to do this correctly, you would have to walk up to the subject, push the exposure lock button, then while holding the button, walk back so that you could get the snow, or sunset back in the photo, and then take your picture. This button allows your camera to choose a setting based on the subject and not on the background, which will in turn let you correctly expose the area of your photo that is most important.


- AZ