[LargeFormat] Focus Shift on Stopping Down

[Ken Hough]

Hi Clive
I was offered the coating from a coater as a " try my work and see if you 
like it." I did and used him for 4 years till he quadrupled his prices!
The Velostigmat was in a Betax 5. I have a wrap around focusing hood so 
45 was entirely possible and 64 was doable after keeping my eyes closed
a few min. The quality difference in B&W was completely nil.
Color was a bit better. You still have to hold the darkslide over that huge 
glass and shade the sky.
Ken

To:             	largeformat@f32.net
From:           	Clive Warren <cocam@cableinet.co.uk>
Subject:        	Re: [LargeFormat] Focus Shift on Stopping Down
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Date sent:      	Sun, 2 Dec 2001 01:23:44 +0000

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>The old timers knew all about this. It was normal on lots of lenses.
>I simply refocus. No big deal.
>Mt 12 in 4.5 Velostigmat I have was a NEW OLD STOCK lens when I un
>earthed it. I disassembled it and had it multi coated.
>Imagine my surprise when I had to change the focus 1/4 in at f 64!
>The good thing is that the shift seems to stabilize at 22 - 64
>Ken

You were just so lucky to find that lens new - probably some premium 
glass at the time it was produced and an expensive item that sold 
fairly slowly to professional chaps. Wasn't the ground glass a bit 
dim at f64 Ken? Guess you were using 8x10 or some pretty serious 
movements on a 5x7......

What shutter is your Velo in?

Did you take any photos for a before and after multicoating to get an 
idea of the change in the image quality?  Maybe you have friends in 
the local multicoating shop to keep the cost down or can opticians 
carry out coating on spectacle lenses? Have read a discussion on this 
subject somewhere, maybe even on this list. Coating a single element 
is no problem but the temperatures involved would probably destroy 
the cement between element groups.....  There again you are a 
recementing fanatic from what I recall ;-)

All these questions and on a Saturday night - well early Sunday 
morning actually.

Cheers,
        Clive

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        ******Ken Hough Photographic Repair******
         Specializing in Deardorff Refinishing
          Lens Recementing and Shutter repair
          Contribitor to McKeowns Price Guide
                   Deardorff Section
           Custom machined Photographic items
           Text Contents Copyright 1999 KHPR
          http://deardorffcameras.0catch.com/
                   Est. 1980