By Kristen Prelipp-Oguntoyinbo

Tip Three – How to Compensate for Auto Exposure

By Kristen Prelipp-Oguntoyinbo Posted March 13, 2012 at 8:49 pm

I began my photography career as photojournalist for newspapers. At the time it was a field dominated by men who held certain, hardcore values. One of which was that it was a sign of weakness to use a tripod, auto focus or auto exposure. I was young and easily influenced at the time so I tried hard to live up to that standard.

Eventually I realized that both auto exposure and auto focus are great tools. When used properly, they can free you up to think more about your image composition and the scene unfolding in front of you. Plus, what good is a great photo if it is improperly exposed? And, I must admit, I even use tripods from time to time now as well.

Auto exposure settings vary from camera to camera. I am a Canon user. But it is universal to have these camera settings:
-       Automatic or Program (P): the camera automatically sets the shutter speed and aperture to suit the subject’s brightness.
-       Manual (M): you set both the shutter speed and aperture desired.
-       Aperture Priority (AV): you set the desired aperture and the camera sets the shutter speed automatically to obtain correct exposure suiting the subject’s brightness.
-       Shutter Priority (TV): you set the desired shutter speed and the camera sets the aperture automatically to obtain correct exposure suiting the subject’s brightness.
I don’t ever use the fully automatic setting. I use the manual setting when indoors or at night most of the time. But I use both aperture and shutter priority constantly when outside. For instance, if I am outside photographing children running around I use shutter priority (TV) to make sure the shutter speed is fast enough to capture the fast action (ie. 1/250 or higher). Or another example would be if I am taking a landscape photo of beautiful scenery, I would use aperture priority to make sure I had deep depth of field (ie. f/11 or higher).

Autoexposure isn’t perfect. A camera sees a scene as grey. The camera doesn’t have a smart, flexible, sentient brain like you. Because they are designed to accurately capture a scene that has an average reflectance of middle gray, your camera is puzzled by setups that don’t fit this ideal. Sometimes you have to override the camera’s auto settings just a bit using exposure compensation. Let’s begin by looking at some of the most common situations where your automatic exposure system will have a problem and then explore how you can easily achieve perfect exposure.

 
Photo Geek Footnote: Using aperture priority- ISO 400 f/8 at 125th of a second.
 
VERY LIGHT SCENES
 
We have not had a proper snow this year so these snow photos date back to Christmas 2010 when it snowed on Christmas Day. Fun! I had my children and two of their cousins over for a sleepover. We all woke up early to play in the winter wonderland. My camera saw the snow as grey, rather than white. So using shutter priority resulted in a dark image as seen above. To lighten a picture, you increase the exposure (+). I do this by either turning the exposure compensation to +1 or +2. Or you may also just switch to manual and set it to one or two stops above the correct exposure.
 
Photo Geek Footnote: Using shutter priority (I wanted a fast shutter speed to catch crazy kids running!)- ISO 400, f/4 at 1/1000th. I set the exposure compensation to plus one. I checked my histogram (see Tip One) to make sure all was well.
 
Photo Geek Footnote: Setting my camera manually (I set it so it was two stops below what was shown as a correct exposure.)- ISO 400, f/3.2 at 0.8 seconds.
 
VERY DARK SCENES
 
In a scene with many dark tones, the camera sees them as all grey. If you let the camera choose your exposure, your image will be too light. So trick it by stopping down one or two f/stops. If you are shooting digitally you need only look at your histogram or preview. If it doesn’t look great, go down another stop.
 
Photo Geek Footnote: In this case I am photographing two incredibly cute, dark-haired children in the studio against a dark background. I am using my studio lights to illuminate, but set them 1 stop lower than I would have for a more middle grey scene.
 
If you missed the second part of this series read it HERE.
 
Please be sure to ask any questions you may have! I am also always open to suggestions for photo stories. You may write me at kpophoto@chapelboro.com. If you don’t want to miss any Snapshots from the Hill posts, please subscribe to the RSS Feed.
Thanks for reading!
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