david_waugh3 Posted January 19, 2009 Share Posted January 19, 2009 <p>My 500cm is about to have a CLA to replace the foam underneath the mirror (amongst other things). Camera has been great but everything has been back-focusing. It was interesting to hear from the Blad tech that the foam really only has a 7 year lifespan regardless of use. I guess this is one little advantage of the 503 and the gliding mirror. Anyway, no big deal, and seven years is a long time without a service anyway.</p> <p>The tech simply 'felt' to see how the foam was and could tell immediately I was having focus issues (even before I said something). I was wondering how to best test for focus accuracy when looking at other bodies. I just put my 500cm on a tripod and focused on something that should have been 0.9m away (80mm Planar) and then measured the real distance which was in fact about 10cm behind. In order to be as accurate as possible, I am assuming one would measure from the back of the lens (ie. front of the body)? Or is is in fact the mirror? I know it might be a little crude, but I assume the front of the body would be close enough... if someone could confirm this I'd be most grateful. I am a little stuck without a body and need to use one over the weekend. I have just enough time to borrow one from a local photographer and put a test roll through it, but thought I could at least do a focus test to ensure I don't have the same issue.</p> <p>BTW - if anyone in Australia needs Hasselblad servicing, I can certainly recommend Eric Owen in Brisbane - he's been a wonderful help.</p> <p>Many thanks,</p> <p>David</p> <p> </p> Link to comment Share on other sites More sharing options...
chauncey_walden Posted January 19, 2009 Share Posted January 19, 2009 <p>David, the focus distance is measured from the film plane.</p> Link to comment Share on other sites More sharing options...
q.g._de_bakker Posted January 19, 2009 Share Posted January 19, 2009 <p>You measure from the film plane mark on the magazine.<br />Which is about 7 cm behind the front of the camera.</p> <p>But instead of measuring, a film test would be better. Set a ruler, with scale, at an angle to the camera/film plane, focus carefully on one scale mark, and take a picture. After processing you will see if the mark you focussed on is in focus or not.<br />You must note what mark you focussed on (easy to forget ;-) ).<br />And obviously the precision is greater the closer the thing is to the camera. So your use of the lens at its close focus limit is good. Using extension (tubes, bellows) between lens and camera is even better.</p> <p> </p> Link to comment Share on other sites More sharing options...
david_waugh3 Posted January 19, 2009 Author Share Posted January 19, 2009 <p>Film plane of course! Silly me. Thanks for the help. </p> Link to comment Share on other sites More sharing options...
zeca_moraes Posted January 19, 2009 Share Posted January 19, 2009 <p>Do the same setup but open the film back and gently put a piece of groundglass on the film plane and confer both focus, from the film plane and from the viewer.</p> Link to comment Share on other sites More sharing options...
ilkka Posted January 19, 2009 Share Posted January 19, 2009 <p>Replacing film back with a groundglass is easy if you have the groundglass back built for the camera. Otherwise it is a bit more tricky since you have to find a way to position the groundglass exactly at the plane where the film would be. That is not flush against the back of the camera, but a little bit behind it. I would guess that 1/10 mm error will show up since you are trying to determine the exact plane of focus, not make a rough composition. Much easier to do as GQ suggested and make a test exposure. Put a pencil mark on the angled paper you are focusing on to mark the exact spot without relying on your memory. This is a good test to carry out once in a while with all cameras.</p> Link to comment Share on other sites More sharing options...
david_waugh3 Posted January 19, 2009 Author Share Posted January 19, 2009 <p>Thanks very much. Will try it tonight. Looks as though my focusing is out about 3cm wide open at closest focus.</p> Link to comment Share on other sites More sharing options...
zeca_moraes Posted January 21, 2009 Share Posted January 21, 2009 <p>From other answers on this forum I would guess maybe the foam where the mirror sits is worn out and needs to be replaced.</p> Link to comment Share on other sites More sharing options...
q.g._de_bakker Posted January 22, 2009 Share Posted January 22, 2009 <p>Zeca,</p> <p>How about "from the original post", instead of "from other answers in this forum"?<br> Takes the guessing out of the game.<br> ;-)</p> Link to comment Share on other sites More sharing options...
zeca_moraes Posted January 22, 2009 Share Posted January 22, 2009 <p>Because it's not from the original post of this thread, but from answers to other posts in this same forum, which I unhappily don't remember. I'm not an english speaker, I write from Brazil, so, sorry for an occasional misunderstanding.</p> Link to comment Share on other sites More sharing options...
q.g._de_bakker Posted January 22, 2009 Share Posted January 22, 2009 <p>No need to apologize. Note the ;-)</p> <p>Still with a wink: if you had read the first post as well as that other thread...<br> ;-)</p> Link to comment Share on other sites More sharing options...
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