Wayne,
From my memory of school physics, probably not really applicable in this
instance, but if a lens is positioned from a subject at its focal length, the
rays coming from the rear are parallel, thus simulating infinity.
In your case, using this basic principle, it does not matter how far from the
image or viewfinder lens it is, the Rolleinar will emit parallel rays to the
camera's lenses which can be set at infinity. The calculations for the angle of
rays for subjects not at the Rolleinar's focal length is beyond my knowledge
but within certain parameters, it should not make any material difference. I
stand to be corrected on this point.
The principle of this can be used to check the accurate focus of a camera lens
at its infinity setting...
A camera with known accurate infinity setting is set up with a ground glass (or
similar) screen marked with a fine pattern/crossing lines, its back and shutter
open with a light behind it. The camera to be checked is set up looking
directly at the first camera. Depending on whether it is a viewfinder or SLR,
with its shutter open or not as the case may be. If the infinity setting on the
camera to be checked is accurate, the image of the fine marking should be
sharp. If not, the lens to focal plane distance should be adjusted.
The distance between the cameras is not important because the rays coming from
the projecting camera are parallel, hence perceived as coming from an infinite
distance.
John
________________________________
From: rollei_list-bounce@xxxxxxxxxxxxx <rollei_list-bounce@xxxxxxxxxxxxx> on
behalf of wayne pinney <tennjed@xxxxxxxxxxx>
Sent: 07 December 2021 22:36
To: rollei_list@xxxxxxxxxxxxx <rollei_list@xxxxxxxxxxxxx>
Subject: [rollei_list] Rolleiflex Old Standard/Rolleinar
I have noticed, on just about every Old Standard I have had a chance to look
at, and even on my own two cameras, that the ring surrounding the taking lens
and/or the viewing lens does not protrude from the front plate far enough to
allow pushing the Rolleinar lenses fully onto the ring surrounding the lens. I
assume that if the Rolleinar lenses do not bottom out on the edge of the lens
ring, focus will be incorrect. Am I correct in this assumption?
Both of my cameras do focus correctly, without the Rolleinars. So I assume the
taking and viewing lenses are properly adjusted.
Best,
Wayne---
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