[rollei_list] Re: Zeiss Ikoflex Lens Issue
----- 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. 

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Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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