IT'S ALL ABOUT THE AMOUNT OF LIGHT PASSING THROUGH THE LENS
When a photograph receives too much light, it is over-exposed. An image is under-exposed when it receives too little light.
The very contrasty image above on Fisherman's Wharf of a fisherman cleaning fish with a very interested pelican supervising shows both severly underexposed and overexposed areas. (Fill flash or the judicious use of a reflector could have been used to improve the picture's illumination by bringing more light onto the scene's very dark shadow areas.)
OVEREXPOSURE
Overexposure results in a loss of resolution (very fine detail), more graininess and less detail in highlight areas.
UNDEREXPOSURE
Underexposure results in a general overall darkness, producing loss of detail in the subject’s dark areas, which, in extreme, can become almost completely black and featureless.
The image on the left is overexposed with a complete loss of detail in highlight areas, while the one on the right is underexposed, losing detail in shadow areas.
WHICH IS MORE HARMFUL?
It depends whether you are shooting digitally, or with negative or transparency film. It also depends on whether you are shooting black and white film or color film. Black and white films generally have more "exposure latitude" than color film. (A film's exposure latitude determines how much it can be under-exposed or over-exposed and still produce usable images.)
For negative films (or print films, as they are sometimes called), underexposure can be more harmful than overexposure. Details in an underexposed scene’s dark areas may not be captured by the film at all, whereas over-exposure that is not too severe might capture some detail in highlight areas that may still be printed using special darkroom techniques.
Remember - It is safer to slightly overexpose negative film than it is to underexpose it.
When an image is horribly over-exposed, it lacks sufficient detail to be salvaged, and should simply be discarded.
For transparency films (slide films), the reverse is true, since slide film is a positive material, not a negative material. Slightly underexposing slide film is safer than overexposing it. The same is true for most digital photography, which stands a better chance of obtaining a properly-exposed picture when it is either properly-exposed in the first place (preferable) or slightly underexposed (the better of two evils).
Since underexposing slide film or a digital image by a small amount is safer than overexposing it, many professional photographers will consistently underexpose some slide films on purpose. Why? Because they wish to ensure there will be sufficient detail in highlight areas. (Note: In professional photographer's jargon, they are not "underexposing" the film even though they technically are. Over-exposing and under-exposing are mistakes, and they are not making a mistake. They are increasing or decreasing exposure. It is all semantics, of course, but intentional over- or underexposure is known as increasing or decreasing exposure.)
A grossly-underexposed picture like this one above is too dark overall to be fixed, digitally or in a print lab.
Most scenes you will photograph contain uneven lighting. Some areas will be underexposed while others may be overexposed. If the lighting was even overall, it would likely look flat and boring. Your task is to photograph a scene so that its important areas - those that are essential to telling your picture's story - are exposed the way you want them to look.
This may mean that some areas will have to be severely over or under-exposed so that detail can be seen in the image's important areas. If your center of interest is washed out (overexposed) or too dark (underexposed), then your image will probably not be what you want. But if your center of interest is properly exposed so that all detail can be seen, then you may have to sacrifice proper exposure for other areas. These are what we call the image's highlights and shadow areas. In many cases, you want them to be very bright or very dark so that your picture looks its best. An image of a properly-exposed subject, say a person standing in bright light in front of a darker area, may look terrific even though the background is tremendously underexposed and dark, because that person (or rabbit, as in the image below) is your image's center of interest and the background isn't.
Most pictures you will take will contain overexposed and underexposed areas. But, if your picture's center of interest is properly exposed, the darker and brighter areas can provide your picture with mood and give you a quality photograph.
Some top photographers (the late Yousuf Karsh, for example) are masters at producing images that contain highlights and shadow areas that are neither too dark nor too bright, but that contain sufficient detail overall in the picture's center of interest. In Karsh's case, the center of interest was typically a person, usually a very famous person, since his expertise and renown were in top-quality portraiture.
Both shadow areas and highlights shown in his subjects contained remarkable detail, with just the right amount of overexposure or underexposure where it was needed, as you can see in this fine example below, a portrait made by Karsh of Albert Einstein, provided courtesy of the Estate of Yousuf Karsh. To view more of his superb images and read the stories behind them, we invite you to visit www.karsh.org.
A true master of his craft, Karsh carefully controlled the lighting for his superb portraits. When Mother Nature is in charge of the light falling on your subject, you will often have to decide whether to shoot for highlights or shadow detail, or an average brightness.
Portrait of Albert Einstein, 1948 - © The Estate of Yousuf Karsh. All Rights Reserved.
| Of his portrait session with Albert Einstein, Karsh said: "At Princeton’s Institute for Advanced Study, I found Einstein a simple, kindly, almost childlike man, too great for any of the postures of eminence. One did not have to understand his science to feel the power of his mind or the force of his personality. He spoke sadly, yet serenely, as one who had looked into the universe, far past mankind’s small affairs. When I asked him what the world would be like were another atomic bomb to be dropped, he replied wearily, 'Alas, we will no longer be able to hear the music of Mozart.'" |
PURPOSEFULLY OVER-EXPOSING THE BACKGROUND
You can create an attractive picture - particularly a person's portrait outdoors - by deliberately over-exposing the background under certain conditions. It even works indoors, too.
Click here - Overexpose the background - and we'll show you how.
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