[rollei_list] Re: "Kaligar" Telephoto Accessory lens for Rollei Automat
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sun, 26 Feb 2006 18:08:32 -0800
----- Original Message -----
From: "SandyF" <sbf70@xxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Cc: <cvug@xxxxxxxxxxxxxxx>; <camera-fix@xxxxxxxxxxxxxxx>;
<idcc@xxxxxxxxxxxxxx>
Sent: Saturday, February 25, 2006 1:09 PM
Subject: [rollei_list] "Kaligar" Telephoto Accessory lens
for Rollei Automat
A while back, I bought a "Kaligar" Telephoto Accessory lens
for my Rollei Automat. I haven't used it for months, and
now can't remember if this Accessory lens changes the
effective speed of the f/3.5 75mm Tessar, thereby requiring
changes in the exposure settings.
If anyone can help, it would be greatly appreciated.
TIA
Sandy F. Ö¿Ö¬
An afocal attachment has no effect on the stop scale. The
entrance pupil is magnified (or reduced) in the same ratio
as the focal length, so the ratio of its size to the FL
remains the same.
The entrance pupil is the image of the stop as seen from
the front of the lens. Its size is the _effective_ size of
the stop.
This is true for both afocal attachments and for simple
diopter mensicus lenses. The difference is that the menicus
type has no correction and will introduce aberrations into
the optical system where the afocal attachment is at least
partially corrected so the optical properties of the system
are likely to be better.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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