The aperture stop is the rim of the focusing paraboloid, thus the feed flat has to be slightly larger than the on-axis diameter required to maximize illumination over the desired field.
22.
In some contexts, especially in photography and astronomy, " aperture " refers to the " diameter " of the aperture stop rather than the physical stop or the opening itself.
23.
This hole is termed the " stop " or " diaphragm "; Abbe used the term " aperture stop " for both the hole and the limiting margin of the lens.
24.
The 8mm f3.5 fisheye, 14mm, 16mm, 24mm, 35mm and 85mm lenses are also sold as " cine " variants with clickless aperture stops, T stops and follow focus gears.
25.
This is usually a maximum power ( in W ) or energy ( in J ) that can be emitted in a specified wavelength range and exposure time that passes through a specified aperture stop at a specified distance.
26.
In 1812 Wollaston adapted it as a lens for the camera obscura by mounting it with the concave side facing outward with an aperture stop in front of it, making the lens reasonably sharp over a wide field.
27.
T-stops were " true " or effective aperture stops and were common for motion picture lenses, so that a cinematographer could ensure that consistent exposures were made by all the different lenses used to make a movie.
28.
If the system be entirely behind the aperture stop, then this is itself the entrance pupil ( " front stop " ); if entirely in front, it is the exit pupil ( " back stop " ).
29.
The ExpSim LV of its EOS lens DSLRs could achieve the same'exposure simulation'effect in both aperture stop-down mode and aperture wide open of its EOS lenses, even if the aperture selection was narrower than widest diameter ( wide open ).
30.
Although he did not yet have access to Ernst Abbe's theory of stops and pupils, which was made widely available by Siegfried Czapski in 1893, Dallmeyer knew that his " working aperture " was not the same as the physical diameter of the aperture stop:
