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NOTE: In order to compensate focusing when normal positioning may be altered due to extreme
temperature change, the focusing ring has been designed to allow rotation beyond the xed
marks of the distance scale. To avoid mistakes, always focus while looking through the view nder.
NOTE: No adjustments in focusing are necessary when taking infrared photography as required
with normal lenses.
4. Light and Contrast Control
Since the re ex lens is not equipped with a diaphragm system, the use of lters plays an important factor in
the control of light and contrast.
5. Filters
Normal (IA Skylight): This lter should be used when no other lters are necessary.
ND 2X & ND 4X (Neutral Density): These lters control the passage of light since no diaphragm
is provided in the lens. Exposure factor is 4X with a ND4X, so that the light intake through the
lens is decreased as if a similar lens were stopped-down by 2 stops. Note that ND lters reduce
light passage only, while the depth of eld is not changed.
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