[rollei_list] Re: Zeiss Ikoflex Lens Issue
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Fri, 29 Dec 2006 10:43:18 -0800
----- Original Message -----
From: <eroustom@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Friday, December 29, 2006 10:19 AM
Subject: [rollei_list] Re: Zeiss Ikoflex Lens Issue
Richard, that's the generous spirit that defines the best
of email user groups!
To check focus on a camera I was playing with, I took a
clean thin sheet of tracing paper and afixed in the place
the film would be, with the back open - with a towel over
the back of the camera and my head, and the shutter locked
open (B and cable), I could see pretty much what the film
would "see". Is there a better, less silly way to do it?
Elias
I use a scrap of ground glass. You can also use clear
glass with some sort of diffusing surface, even Scotch Magic
Tape will do but the spray on diffusing lacquer is probably
better. The glass should sit against the film rails. The
actual position of the film in the camera during use may be
slightly different due to film bowing but there is no way to
predict that reliably. Another useful focusing tool is the
Rollei plate or sheet film adaptor, it has a ground glass
back.
The ground glass is used to determine the focus of the
taking lens. It is also used for setting the infinity stop.
On most Rolleis the infinity stop is just a boss on the
focus knob. The viewing lens can be set at any distance but
it may be easier to see when both lenses are sharply focused
for distant subjects. I am not sure how the infinity setting
is changed for the Ikoflex.
Its probably good practice to check the taking lens for
"focus shift" this is a change in the point of best focus
when the lens is stopped down. Most lenses have a little.
For an f/3.5 Tessar it will be noticable between wide open
and about f/8. Its probably a good idea to compromise the
focus adjustment to compensate for it.
I find I need at least a 10X lens to see critical focus,
more would be better if you have a really good magnifier.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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