The entrance pupil diameter is not necessarily equal to the aperture stop diameter, because of the magnifying effect of lens elements in front of the aperture.
12.
For a simple lens, which is what's shown, the aperture stop would have to be located at the lens, not behind it.
13.
In astronomy, the diameter of the aperture stop ( called the " aperture " ) is a critical parameter in the design of a telescope.
14.
It is still defined as the focal length f of an objective divided by its diameter D or by the diameter of an aperture stop in the system:
15.
When it is mounted on a compatible Nikon camera, the user can use all exposure modes to take photographs without operating the aperture stop-down button.
16.
All rays which issue from O and pass through the aperture stop also pass through the entrance and exit pupils, since these are images of the aperture stop.
17.
All rays which issue from O and pass through the aperture stop also pass through the entrance and exit pupils, since these are images of the aperture stop.
18.
For example, in a telescope, the aperture stop is typically the edges of the objective lens or mirror ( or of the mount that holds it ).
19.
Placing an aperture stop, or making the lens smaller, just means that fewer rays get through & mdash; not that part of the scene gets cut off.
20.
In addition to an aperture stop, a photographic lens may have one or more " field stops ", which limit the system's field of view.
