Reducing Digital Noise

Digital noise is the polka-dot effect in images with long exposures or images shot at high ISO settings in low-light situations. The effect is most noticeable in images shot in low-light situations. Many consider digital noise to be a synonym for film grain. Although the causes are the same, the effects are quite different. Some film photographers purposely shoot images with enhanced grain for artistic effect.

Using Reciprocity to Compose Your Image

You can adjust the aperture setting and shutter speed to create several different correctly exposed images. The relationship between the aperture and shutter is known as reciprocity. Reciprocity gives the photographer control over the depth of field of the Image, which controls the area of the image that remains in focus. This is the easiest way to control what part of the image you want the viewer to pay attention to.

For example, opening the fens aperture by one stop and decreasing the shutter speed by one stop results in the same exposure. Closing the aperture by one stop and increasing the shutter speed by one stop achieves the same exposure as well. Therefor, f4 at 1/90 of second is equal to f5.6 at 1/45 of a second. The reason is that the camera's aperture setting and shutter speed combine to create the correct exposure of an image.

Depth of Field

Depth of field is the area of the image that appears in focus from foreground to background and is determined by a combination of the opening of the aperture and the focal length of the lens. A small aperture setting results in greater depth of field. Controlling depth of field is one of the easiest ways for a photographer to compose the image.

Understanding F-Stop and Lens Speed

f-stop

The photographer adjusts the opening of the aperture by setting the f-stop. An f-stop is a ratio of the focal length of the lens to the diameter of the opening of the aperture. For example, a 50 mm lens with an aperture opened up to a diameter of 12.5 mm results in an f-stop of f4 (50 ÷ 12.5 = 4).

Aperture

The aperture is the opening in the lens (created by an adjustable iris or diaphragm) that allows light to pass through. The exposure of the image is determined by the combination of shutter speed and the opening of the aperture. The larger the aperture, the more light is allowed to pass through the lens. The aperture is measured in f-stops, and each stop represents a factor of two in the amount of light admitted. The aperture setting (f-stop), combined with the focal length of the lens, determines the depth of field of an image. For more information on depth of field.