[rollei_list] Re: Identifying a strange Rollei TLR accessory : B-II Rf x 3,5 disc
- From: Bigler Emmanuel <Emmanuel.Bigler@xxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Tue, 26 Jun 2012 12:16:14 +0200
----- Original Message ----- From: "Harry Fleenor"
<harry@xxxxxxxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, June 25, 2012 4:11 PM
Subject: [rollei_list] Re: Identifying a strange Rollei TLR accessory :
B-II Rf x 3,5 disc
This is a tool used in adjusting the focus of the viewing lens on
Rolleiflexes with a 3.5 lens that take that bayonetted size.
Thank You Harry Fleenor
From Richard Knoppow :
That is extremely interesting. If I understand right it is used on the
viewing lens when setting focus. If so it would shift the focus slightly
from that at wide open perhaps giving a better average match to the
taking lens. While these lenses are very well corrected they still have
a little spherical aberration and thus a little focus shift. I wonder if
the infinity stop is set for the taking lens wide open.
Richard Knoppow
Thank you Harry & Richard.
Hence this object is a very specialized Rollei tool, like the thickness
gauge used to properly adjust the film roller-feeler system. Something
that ordinary Rolleiphiles should never see ;-) Restricted use for
serious Rollei professionals only ;-)
I was thinking about a device to actually help the user to see the depth
of field as it will be when the taking lens is stopped down to the
working aperture.
But as Richard suggests, it does make sense that the proper focus
adjustement of the viewing lens should be made at a "f-number" closer to
the best f-stop of the taking lens, 5.6 or 8 according to various tests
that have been made since post-war Rolleiflex exist ;-)
I hope that Richard will forgive me if I attempt to "split hair" in the
discussion : actually this auxiliary aperture not being located inside
the triplet lens, is certainly not located where the diaphragm is
usually located in a real triplet taking lens. Hence residual
aberrations will be sligthly different ???
A Rollei mystery solved : Thanks to the Rollei Users List !
--
Emmanuel
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