RE: Optics question (not alt)

From: joachim oppenheimer ^lt;>
Date: 03/09/05-07:01:25 PM Z
Message-id: <>

I don't know if this helps: I have a copy of Richard W. St.Clair, A.R.P.S.,
"Photographic Lenses and shutters" (1940) page 55, and I quote: QUOTE:
Determining effective aperture: In the case of a single lens, with the iris
placed in front of the lens, the effective aperture is the diameter of this
stop opening. All of the light that enters must enter through this aperture.
But, in the case of multi-element lenses the light beam entering the front
lens is slightly converged or condensed by the front lens element before it
reaches the iris which, in this type of objective, is placed between the
front and the rear elements. The diameter of the beam is now less at the
iris than at the point of entry and the whole matter is rather uncertain.
END QUOTE. If I understand your question correctly, and since virtually all
modern lenses are compound lenses, I would conclude that the image size (on
film or sensor) will be smaller but in a unpredictable way depending on the
specifics of the lenses and related factors (focal distances, etc.) Joe

-----Original Message-----
From: []
Sent: Wednesday, March 09, 2005 6:59 PM
Subject: Optics question (not alt)

Am I remembering something incorrectly or does image size on the
film/chip plane change with aperture? I could swear it does but I don't
know from where I pulled that info. Or, perhaps I'm just losing my mind.

I'm helping a friend edit a chapter in his book and sure don't want to
suggest something wacky.

Thanks in advance for input.

Received on Wed Mar 9 19:01:49 2005

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