EXPOSURE MEASUREMENT — continued
For subjects of uniform brightness, a reading may be taken from any part of the subject. However, if the lighting is harsh or contrasty, move up close and measure the light falling on the most important part of the subject. If the picture includes an unusually bright source of light such as a light bulb or expanse of sky, move the camera so that the light source does not dominate the viewfinder while you make your reading. For backlighted subjects, move up close and include dark areas of the subject.
Keep out stray light! The finder is designed to minimize the effect of light entering through the finder eyepiece under normal conditions. However, in the following situations, the use of a finder eyecup is recommended.
- When the camera is in sunlight and the subject is in shade.
- When the stop-down method is used at small apertures.
- When a shaft of sunlight falls between the eye and the eyepiece.
When the needle on top of the finder is used to determine exposure, the eyepiece should be covered with the hand to prevent extraneous light from entering the finder.
1) Measuring the bright area in the center of the screen will cause underexposure of the main subject.
2) For correct exposure, first measure the light striking the main subject, then compose and shoot.
DEPTH OF FIELD
Depth of field refers to a zone extending in front of and behind the plane of sharpest focus. Within this zone, blur (or unsharpness of the image) will be negligible and everything can be accepted as in sharp focus. Depth of field extends a greater distance behind the subject in focus than in front. Depth of field depends on three factors: focal length of the lens, lens-to-subject distance and aperture. The smaller the aperture and the shorter the focal length of the lens, the greater the depth of field. Also, the closer the subject, the smaller the depth of field. These three factors can be adjusted independently or in combination to give the photographer creative control over the final picture.
Depth-of-Field Preview Button
The depth-of-field preview button lets you check depth of field before shooting and make desired adjustments. Press the button and the lens stops down to the preselected aperture to allow you to see how much background or foreground Is in or out of focus.
DEPTH OF FIELD — continued
Depth of field can also be read from the color-coded scale engraved on the lens. The pairs of colored lines correspond to f/numbers of the same color. To find the depth of field at a particular aperture, first focus the lens on the subject. Then check the numbers on the distance scale opposite the colored lines which match the taking aperture of the corresponding color to find the depth of field at that aperture. For example, f/16 on the aperture ring of the 50mm f/1.4 lens is blue. With the lens pre-focused at 17 feet (Sm), the numbers on the distance scale opposite the blue lines show that depth of field extends from 9 feet (2.7m) to infinity (09).
By stopping down the lens only, the depth of field can be increased, as illustrated by the following three photographs: