الأربعاء، 13 أبريل 2011

Color and Saturation

There is another aspect of color that is important to the photographer: saturation. From the photographer's point of view, saturation refers to the intensity of the color. A color that is very vivid is a saturated color. Colors that appear dull or washed out are unsaturated colors. From a technical viewpoint, saturation refers to how much white light is mixed in with the color. Saturated colors contain very little or no white light. That is why they are very vivid. Unsaturated colors have been diluted by the addition of white light.
Figure 4: Saturated Colors
Figure 4 shows an image with saturated colors. The colors are fairly vivid and pleasing to the eye. In particular, the reds, oranges, and yellows of the leaf stand out. The objects in the image are actually rather mundane; it is the saturated colors that define this image.
Figure 5: Desaturated Colors
Figure 5 shows what an image with desaturated colors looks like. In particular, the greens of the grass and bushes are relatively washed out. This is a result of the image being shot in unfavorable light (yes, I know better, but I was hiking through this area at mid day and decided to take an "I was here, too" shot).
Since color affects the mood and impact of an image, saturation becomes important. Often, photographers want rich, intense colors. Sunsets are an example of this. The best sunset images contain very saturated colors. Therefore, photographers need to understand what factors can be used to control saturation.
One of the biggest factors that affects saturation is time of day. Early morning and late afternoon generally provide more saturated colors than mid-day. If you look at the landscapes of some of the most successful photographers, you will find that most of their images were taken early or late in the day, partly, for this reason.
A polarizer filter is another way that can be used, in many situations, to increase the saturation of colors. Part of the light that dilutes saturation is polarized light. Polarized light is light that vibrates only in one direction (this has to do with the electromagnetic waves of which light is composed). A polarizer can reduce the amount of polarized light and improve the saturation of the colors. However, a polarizer is not equally effective under all circumstances. A polarizer has the greatest affect when the camera is pointed at right angles (perpendicular) to the direction of the sunlight.
Figure 6: Optimum Polarizer Angle
Figure 6 shows the optimum positioning of the camera, in relation to the object to be photographed and the sun, for the maximum polarizer effect. As the camera moves away from this perpendicular position, the affect of the polarizer is reduced. If the light is coming directly from behind or in front of the camera lens, the polarizer will have no affect at all.
Polarizers can cause problems with wide angle shots. With wide angle lenses, the angle from the camera to the objects changes, relative to the direction of the sunlight, depending on where the object is located in the wide field of view. Thus, the polarizer will have a different affect on different parts of the wide angle image. A typical example of this is a wide angle shot of a landscape where a polarizer was used. The saturation of the blue in the sky may change across the sky due to this polarizer affect.
Another factor that can affect saturation is exposure. An image may get different amounts of saturation depending on how much exposure is given. For instance, photographers that use slide film often underexpose by about a half stop to increase the saturation of the image. The affect that exposure has on saturation varies depending on what film/sensor is used, the color, and other factors. This makes it difficult to predict the impact that changes in exposure will have on saturation. The best advice is to bracket the exposures. Then, pick the best image from the bracketed exposures.

http://www.ronbigelow.com/articles/light/light.htm

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