[rollei_list] Re: Bellows on 2.8D?...an answer from Mr Prochnow
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 20 Aug 2005 17:42:57 -0700
----- Original Message -----
From: "Carlos Manuel Freaza" <cmfreaza@xxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Saturday, August 20, 2005 4:56 PM
Subject: [rollei_list] Re: Bellows on 2.8D?...an answer from
Mr Prochnow
I think he understood the question Patric, he answered
that the ring in the back of the lens is like a
diaphragm to save quality in difficult situations;
difficult situations are a strong backlight photo, a
photo where the sun appears directly, some other
strong light source, the diaphragm could help to save
image quality, that is its function, a light trap.
The second part could need more explanation. I
commented him in the last part of my question that I
had not seen the diaphragm in the Rolleicord IV (I'll
look again tonight), and then he answers that the
diaphragm can look different for every calculation, I
think he meant that the diaphragm is calculated
different for different models and then they look
different. In fact my Rolleiflex 2.8C 2.8/80 Xenotar
and my Rolleicord IV 3.5/75 Xenar look very different
in the taking lens back and both are like new in this
part.-
All the best
Carlos
Aha!!! I just looked at three Rolleiflex's and my
Rolleicord IV. There is a short tube at the back of the
taking lens in the two older Rolleis (an "Old Standard" and
a late MX), this tube appears to act as a sort of internal
lens shade. The Rolleiflex 2.8E does NOT have this tube,
rather it has the short bellows (or diaphragm or membrane or
whatever). This also appears to act to prevent scattering of
extra-image light, at least when the focus is racked out.
Rollei seems to have payed a lot of attention to
preventing internal reflections. The inner tube or bellows
and the light baffles in the later cameras for instance.
Rollei also has an effective lens shade.
BTW, none of this stuff is effective for bright light IN
the image, such as shooting into the sun. A lens shade works
primarily to eliminate flare or ghost images from
extra-image light getting into the lens. It can also limit
the amount of extra-image light where the lens coverage is
significantly larger than the film. The internal tube acts
as a crude field stop limiting the projected light from the
lens from striking anything but the film. The baffles tend
to stop reflection of light that does strike the internal
surfaces of the camera which otherwise would strike the film
causing flare. I have discovered by shining a flashlight
into a Rollei that the edges of these baffles can reflect a
surprizing amount of light despite being painted with a good
anti-reflection paint.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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