b. There are two ways to check the uniformity of illumination on the original. You can use an
exposure meter, or a pencil, or other long thin object.
(1) When checking with a meter, you are not interested in exposure at this time, only even
lighting. Take a reading of the center of the copy, then read the four corners of the copy. All readings
should be the same. If not, adjust the lights until all areas receive the same amount of light. Do not read
the shadows of your hand or the meter.
(2) When using a pencil or similar object, place the pencil perpendicular and centered on the
copy. Make sure you place the blunt end and not the sharp end against the copy. The shadows cast by
the pencil should be of equal darkness, if not, move the lights until all shadows are equal. Remember
that this method is only used to check for uniformity. An exposure must still be taken.
c. To obtain uniform lighting, use at least two lights. Locate one on either side of the camera.
Place the lights so there is a 45-degree angle between the light and the original, and between the light
and the camera (fig 3-3).
Figure 3-3. Uniform lighting
d. As shown in Figure 3-4, the angle between the light and the camera should be reduced for
original with textured surfaces. Textured surfaces diffuse the light so you need a more direct light to
prevent shadows and to reflect more light to the lens.