Exposure compensation should be applied when the camera's meter doesn't get the exposure "right" by itself. This can be due to contrast in the scene (e.g. large bright areas may cause the meter to under-expose the shadows or vice versa) or when a special effect is desirable (e.g. if you want to deliberately underexpose for a silhouette).
If you have a digital camera capable of showing a histogram, it should be very easy to decide whether compensation is needed. Just make one exposure at the meter reading, examine the result and correct as necessary.
If you're photographing fast-moving subjects and don't think you can get a second chance, it helps to pre-meter the scene or apply any correction you think you'll need ahead of time.
As far as how to use exposure compensation, if you're shooting in manual mode, you simply under or over expose as needed. If you're using an auto exposure mode such as Aperture Priority, then there's a button and/or wheel to use. You'll need to consult your camera manual, which should also include some basic explanation of exposure compensation as well..
In general, if the overall scene is lighter than medium (a field of snow) then you would us + exposure compensation. If a scene is darker than medium (a forest of evergreen trees) you would use minus compensation
To really understand the whys and whens of exposure compensation, there are many books out there by authors such as John Shaw or Brian Peterson that explain it all very well. You should also be able to find a ton of online articles about exposure.
Scott, you have received advice from two of the best photographers here on NPN. Only thing I would add is that if you are shooting digital look for the "blinkies" on your LCD screen. these areas are over exposed. You have to decide if they are important areas, such as white bird feathers in the main subject, to dial in under exposure correction - usually no more than - 2/3 or so. The histogram and blinkies are your best in the field teachers.
I agree with everything said so far, but feel the need to add a third "scenario" when exposure compensation is needed. In some circumstances such as action moving quickly through different lighting, it's simply impossible to keep pace with manual settings. That's when you have to know (and trust) the program settings on your camera. I've done a whole bunch of photography of kids in science camps for example, and they're moving indoors and out, into sun and back to shade, and in circles faster than most adults can keep up with, much less while making camera adjustments. You have to shoot in program mode and fill with flash or simply miss the shots.
In this case I shoot on program, but with a finger on the plus minus button and a thumb on the adjustment dial. A bright window behind the subject or directly backlit and I'll automatically dial in some plus. Move the subject outdoors against dark spruce trees in the shade, and here comes the minus. It's all happening very fast, and ultimately you quit thinking about it and simply react. Experience and disappointment in results will quickly teach you what you should have done, and you'll remember it the next time you encounter similar circumstances.
And as an afterword, it's worth pointing out that until very recent models and meters emerged I did NOT trust program settings on cameras, based upon pretty careful testing beforehand. Yup, I missed lots of shots but stuck with manual in spite. Results of tests of my current camera (D2X) were so startlingly good, I now have no qualms about program settings, so long as a little exposure compensation is dialed in when circumstances call for it.
Exposure compensation was also used in the good ole' film days to underexpose slide film a tad bit (if the slide was to be used for projection purposes) in order to boost saturation (though, most photographers would achieve the same result by just overideing the ISO setting to 1/3rd or mor stop faster). Conversely, if the final output was supposed to be print, the slide would be overexposed by a third of a stop (or more). Of course, caution would need to be excercised in either case to prevent the blocking up of shadows where detail was called for, and blowing out of highlights.
Exposure compensation has also been used (both in the film world as well as digital) to render the range of tones across a scene other than what the camera would otherwise render them. For example, to give a dusky look to a daylight shot.
To cut a long story short, exposure compensation is used to place a tone where you want it, rather than letting it fall where it may.
A reading of "the zone system" as applied to slide and digital photography would help you a great deal in understanding zones, tones and exposure theory.
Thanks for the great replies. Not applying exposure compensation might the reason I am having trouble getting sharp focus on the black birds (cormorants, coots, and black necked stilts). Have shot many pictures of these folks and been disappointed with the results.
Great information in a timely manner and I have discovered a whole new area of photography to explore.
Actually, exposure compensation has nothing to do with getting sharp focus. That's an entirely different subject!! You'll probably find quite a bit about achieving sharp images with a quick search of this site. If you don't find what you need, start another thread and we'll jump right in
Discussion
7 repliesWhen, why and how would I use Exposure Compensation?
If you have a digital camera capable of showing a histogram, it should be very easy to decide whether compensation is needed. Just make one exposure at the meter reading, examine the result and correct as necessary.
If you're photographing fast-moving subjects and don't think you can get a second chance, it helps to pre-meter the scene or apply any correction you think you'll need ahead of time.
Guy
In general, if the overall scene is lighter than medium (a field of snow) then you would us + exposure compensation. If a scene is darker than medium (a forest of evergreen trees) you would use minus compensation
To really understand the whys and whens of exposure compensation, there are many books out there by authors such as John Shaw or Brian Peterson that explain it all very well. You should also be able to find a ton of online articles about exposure.
In this case I shoot on program, but with a finger on the plus minus button and a thumb on the adjustment dial. A bright window behind the subject or directly backlit and I'll automatically dial in some plus. Move the subject outdoors against dark spruce trees in the shade, and here comes the minus. It's all happening very fast, and ultimately you quit thinking about it and simply react. Experience and disappointment in results will quickly teach you what you should have done, and you'll remember it the next time you encounter similar circumstances.
And as an afterword, it's worth pointing out that until very recent models and meters emerged I did NOT trust program settings on cameras, based upon pretty careful testing beforehand. Yup, I missed lots of shots but stuck with manual in spite. Results of tests of my current camera (D2X) were so startlingly good, I now have no qualms about program settings, so long as a little exposure compensation is dialed in when circumstances call for it.
Exposure compensation was also used in the good ole' film days to underexpose slide film a tad bit (if the slide was to be used for projection purposes) in order to boost saturation (though, most photographers would achieve the same result by just overideing the ISO setting to 1/3rd or mor stop faster). Conversely, if the final output was supposed to be print, the slide would be overexposed by a third of a stop (or more). Of course, caution would need to be excercised in either case to prevent the blocking up of shadows where detail was called for, and blowing out of highlights.
Exposure compensation has also been used (both in the film world as well as digital) to render the range of tones across a scene other than what the camera would otherwise render them. For example, to give a dusky look to a daylight shot.
To cut a long story short, exposure compensation is used to place a tone where you want it, rather than letting it fall where it may.
A reading of "the zone system" as applied to slide and digital photography would help you a great deal in understanding zones, tones and exposure theory.
Hope that helps,
nevilleb
Great information in a timely manner and I have discovered a whole new area of photography to explore.