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03-02-2012, 02:32 PM   #1
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Backfocus with 645 (solved)

Hello

I allwayx had the feeling, that my 645 has some Backfocus - today I finally made doem test shots with a 165/2,8 and found a signigicant backfokus akn all shots - does anybody habe experience how this can be corrected?

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Last edited by klaus123; 03-25-2012 at 07:41 AM. Reason: solved
03-03-2012, 12:40 AM   #2
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Some further input:
- The faulty results have been there already with the original focussing screen and seem to be identical wit the new Microprism-spot screen
- Eye correction is set according to sharp reading of the led-display
- The magazin is a modified 220-type used with 120-type film ....This may be one of the keys (?)
03-03-2012, 01:54 AM   #3
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There is no such thing as back focus with manual focus cameras. Could be a faulty eye or a misaligned screen

It could also be that the third possibility you're listing above is the source of the problem. If the focal plane is even slightly misaligned, you can't expect the focus reading on the screen to be the same as on the film. Why not try things with a stock magazine?

Just for reference, here's what normally causes FF/BF and why it only applies to AF DSLRs: Fixing Front and Back Focus - Causes of Front- and Back-Focus - PentaxForums.com

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03-03-2012, 07:52 AM   #4
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QuoteOriginally posted by Adam Quote
There is no such thing as back focus with manual focus cameras. ....

I strongly disagree this interpretation - but if you like you may call it faulty focus with sharpness behind the intended point.....

I do not assume an eye-issue as manual focus on the 67 and the Microprismen-srreen in the K7 works fine.
I looked to the magazin meanwhile and found, that the Film ist pressed to the body of the camera in a way that the thickness of the film should not have any influence.

On The K7 I was able to dajust the screen using Pentac shims - but these seemnot to be available for the 645.

03-25-2012, 07:39 AM   #5
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Hello

Meanwhile I adjusted the screen by puting some transparent adhesive tape (TESAFilm) on the top side of the screen (left & right side ~ 3mm wide).
It has some negative impact on the viewfinder picture - but focus is right now :-)

Last edited by klaus123; 03-25-2012 at 07:43 AM. Reason: add. Info
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