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Brightness of Light

And its effect on contrast.


Understanding how to deal with shadows is as important for photographers as knowing how to treat light. High contrast results from deep shadow and bright light in the same image.
Understanding how to deal with shadows is as important for photographers as knowing how to treat light. High contrast results from deep shadow and bright light in the same image.

Brightness or intensity is the single most important quality of light. You seldom hear experienced photographers complain about "too much light."

An abundance of light makes possible the use of smaller apertures, faster shutter speeds and slower film or a slower ISO sensitivity in your digital camera, all of which generally make for clearer photos. But brightness is a relative term in photography, since any scene must have bright areas and shadow areas to make a photograph. The photographer must decide upon a combination of brightly-lit and shadowy areas in making good pictures. That combination is called contrast, and controlling contrast is essential to producing good photographs.

The lack of strong shadow indicates an overcast day, producing low contrast illumination, often the best lighting for portraiture.
The lack of strong shadow indicates an overcast day, producing low contrast illumination, often the best lighting for portraiture.

Contrast is a function of the angle at which the light strikes a photographic subject.

High contrast

If all the light rays emanate from more or less the same angle because they come from a single source like the sun or a spotlight, high contrast results, which is harsh with bright planes and dark shadows.

Bright sun on a clear day will generally produce a high contrast situation with its brightly-lit highlights and pronounced, intense shadows. Details disappear in the darkness if you expose for the highlights, and details disappear in the brighter areas if you expose for the shadows. This is especially apparent when shooting with a digital camera or with slide film, both of which have little or no exposure latitude. High contrast light is suitable for compositions that are bold and graphic-oriented, with sharp lines defining the difference between light and shadow, and is unsuitable for emotional, moody images.

When all the light rays emanate from the same angle (from a single source like the sun), high contrast results, which is harsh with bright planes and dark shadows.
When all the light rays emanate from the same angle (from a single source like the sun), high contrast results, which is harsh with bright planes and dark shadows.

Low contrast

Low contrast is soft, and occurs when light comes from several directions because it is reflected (off of walls or a white card, for example) or is diffused (through mist, an overcast sky or a large white sheet, etc.). Shadows are not intensely dark. They are filled in with some light, and contours are less sharply defined. Very low contrast light can seem to come from everywhere, but nowhere in particular, and can result in dream-like images. Be aware, though, that extremely low contrast lighting can produce dull images, lacking definition and masking detail. Correct balance between high and low contrast must be reached.

A common situation in which you find low contrast lighting occurs outdoors when the sky is overcast. The sun's light is diffused by cloud cover, spreading it out and making the entire sky the light source. Your photographic subject is illuminated by light coming from all angles, lightening and sometimes completely eliminating shadows. This kind of low contrast lighting can be ideal for portraits, particularly of women and babies, since it tends to soften features.

An overcast sky diffuses and spreads out its light, resutling in low contrast lighting that reveals details without harsh shadows and bright highlights.
An overcast sky diffuses and spreads out its light, resutling in low contrast lighting that reveals details without harsh shadows and bright highlights.

LIGHT SIZE AND ITS EFFECT ON SHADOWS

Small lights create hard shadows that have crisp edges, while large lights make edges appear softer, which makes shadows diffused, often so gradually diffused that it is hard to discern where they actually begin or end.

A hard shadow doesn't necessarily need to be a dark shadow. For example, if a subject is illuminated by a single, small light source off to the side, there will be hard, dark shadows on the opposite side. If you introduce fill light (by using a reflector, fill flash or another light that is less bright) to bring out detail in the shadow side, the shadow will still be there and will still be sharply-defined - that is, a hard shadow - but it won't be a dark shadow. The contrast is reduced, not eliminated. Using a second or additional light sources to fill in shadow areas, with enough illumination to bring out detail, but not enough to overpower the main light, is very effective in reducing contrast, and standard procedure in studio lighting. In order to use this technique and properly control the amount of contrast, you should know about Lighting ratio.

REDUCING CONTRAST

High contrast light can be altered by the photographer in a number of ways so that it produces low contrast illumination. Electronic flash, for example, can be harsh, creating dark, sharply-defined shadows when placed at an angle to the subject. This light can be softened and diffused. (See Softening the harsh light from a flash.) Strong, direct sunlight is contrasty, but can be altered to produce softer, low contrast light by diffusing it. (See Portable light diffuser.) Reflectors can be used to introduce fill light to the subject's shadow side, reducing contrast. An effective material for this purpose is white styrofoam, but it is only one of many materials that will do the job.

This image has contrast, as all images do, but it is controlled so that the contrast between highlight & shadow areas is balanced. Proper exposure was made for the highlight area, Details there are visible, allowing the shadow area to gradually darken.
This image has contrast, as all images do, but it is controlled so that the contrast between highlight & shadow areas is balanced. Proper exposure was made for the highlight area, Details there are visible, allowing the shadow area to gradually darken.

WHAT IF YOU WANT AN IMAGE THAT HAS HIGH CONTRAST?

To achieve a high contrast image, you simply need a single, strong light source, like direct sunlight on a clear, bright day, for example, or a single, undiffused flash unit held off to one side when the ambient light is dark. If you pose your subject so that the light strikes them from the side and there are no objects on the other side to reflect light into the shadow areas, you will get a high contrast image.

Although the subject of this image is unquestionably soft, the contrast is hard, with highlights washed out. Proper exposure was made for shadow areas, but it could not render detail in the highlight areas, which are pure white.
Although the subject of this image is unquestionably soft, the contrast is hard, with highlights washed out. Proper exposure was made for shadow areas, but it could not render detail in the highlight areas, which are pure white.

If you want a deep, dark shadow side, then take an exposure reading of the light striking the bright side only. This will give you properly-exposed detail on the illuminated side and probably only deep shadow on the shadow side, which is what you seem to be trying to achieve. If you want detail in the shadow side and a markedly overexposed bright side, maybe even washed right out (as in the image above), then take your meter reading from the shadow side only.

If you want some detail in the shadow area, and a moderately over-exposed bright side, then select a meter reading between the two.

Once you have determined your meter reading and know the range of settings you can use for proper exposure, it won't matter whether your shutter speed is fast or slow for high contrast. It's the combination of shutter speed and aperture that determines the exposure. So, don't take a meter reading for the kind of exposure you want and then choose the fastest shutter speed within the range of acceptable settings just because you are seeking a high contrast image. The amount of contrast will remain the same for any combinations that give you proper exposure.

You can, however, influence apparent contrast by increasing or decreasing shutter speed while keeping the aperture the same. This occurs because you are over-exposing or under-exposing the image when you veer away from the correct settings for proper exposure. The contrast actually remains the same, though. You can't change the amount and direction of light that is striking your subject by increasing or decreasing shutter speed. You are only changing the way the film or digital sensor records that light, and are either making the bright areas brighter by overexposure (and also brightening the dark areas, too) or making them both darker by underexposure.

If you are shooting film, you can also choose a high contrast film for starker, harsher contrast between light and dark areas. If you are shooting with a digital camera, your image will have high contrast since digital sensors have almost no exposure latitude.

A single, bright light source (the sun) creates harsh contrast. One side is bright, while the other is dark. Correct exposure was made, in this case, for the dominant bright side. There is no detail visible in shadow areas due to the high contrast.
A single, bright light source (the sun) creates harsh contrast. One side is bright, while the other is dark. Correct exposure was made, in this case, for the dominant bright side. There is no detail visible in shadow areas due to the high contrast.

 
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