NPFC - MIL-F-21241
FILTERS, COLOR, FINISHED (FOR OPTICAL INSTRUMENTS)
| Organization: | NPFC |
| Publication Date: | 4 December 1958 |
| Status: | active |
| Page Count: | 22 |
scope:
This specification covers finished color filters for use in optical instruments. It is not intended to cover polarizing filters.
Filters shall be of the following types, colors, and grades, as specified (see 6.2):
Types:
Type I - Solid glass.
Type II - Laminated.
Colors:
Red.
Yellow.
Aircraft neutral.
Light neutral.
Dark neutral.
Searchlight neutral.
Grades:
Grade A - Adequate for use near the focal plane of an eyepiece.
Grade BT - Adequate for use near a telescope objective lens.
Grade BR - Adequate for use near a rangefinder objective lens.
Grade C - Adequate for use at unit magnification, or with the unaided eye.
intended Use:
Filters covered by this specification are intended for use on optical instruments as follows:
Grade A - Near the focal plane of an eyepiece
Grade B - Near a telescope objective... View More
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