h. Placing the lights farther from the original than the camera also prevents the light from
shining directly into the lens and causing hot or bright spots. There are also other ways bright spots
occur. Light on any smooth surface causes a shiny reflection. Do NOT allow this reflection to be picked
up by the lens. You can keep the shiny reflection out of the lens by moving the light, moving the
reflecting surface, polarizing the light or by using shields (barn doors).
Learning Event 3:
EXPOSING AND PROCESSING THE FILM
1.
Focus the camera.
a. Now that all the equipment and materials are in place, focus the camera by observing the
image on the ground glass back. Besides focusing for a sharp image, also look for possible defects in the
setup such as:
(1) perspective distortion caused by the original not being parallel to the film plane
(2) distortion caused by an original that is not flat
(3) hot spots caused by shiny reflections
(4) improper framing caused by poor alignment of original
(5) reflection of camera from glass-covered easel
b. After focusing, determine the exposure.
2.
How to determine the exposure.
a. First determine the basic exposure. Multiply the exposure meter by reading five for line
copy, or use the gray card reading, or you can use the middle tones directly for continuous-tone copy.
b. Then multiply the basic exposure by the filter factor.
c. When the original-to-lens is less than ten times the focal length of the lens, as it will be most
of the time, you must multiply the exposure by the bellows extension factor (BEF). There are two
methods of calculating the BEF.
(1) The first method is to measure the bellows extension (BE), (distance from lens to focal
plane), divide by the focal length of the lens (FL), and square the result. To square a number, you
multiply it by itself. Stated as a formula this is:
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