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03-06-2008, 03:03 PM   #1
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repair advice inquiry - front focus on *ist DS

Hi-

The following is a request for home repair advice due to some kind of mis-calibration in the manual focus system of my *ist DS. The details of the case are providd below.

I own an *ist DS, which on the whole I'm very happy with, but, at least with my Katz Eye focusing screen, it has a slight problem with manual focus - the distance of optimal focus is consistently right in front of the point I focus on with the split prism. The effect isn't noticeable so long except in situations with fairly limited depth of field, but, since I do a fair amount of available-light and macro shooting, a shallow focal field is a common fact of life for me (and of course, selective focus is sometimes aesthetically desirable). This is only a problem with the manual focus system - AF looks great (in fact, my sense of the problem is confirmed in that, when I auto-focus on a particular point, the thing at that point tends to look somewhat out-of-focus in the viewfinder. I've noticed front focus effecsts with a few different lenses (including the 40mm DA limited and the 50mm f/1.4 M), so it seems like it must be a problem with the camera. This is sometimes not a big deal, but on other occasions it's quite annoying (especially with my beloved old MF lenses).

Paying to get this repaired makes little sense, since the value of an *ist DS on the used market is not much more than the least I could reasonably hope to pay for repairs, and since there's a decent chance that I'm upgrading to another body in the not-too-distant future. On the other hand, for the same reasons, if anybody can tell me what tools I'd need and what I'd have to do, I'd be willing to try repairing the thing myself, since if I'm toying with the idea of upgrading anyway, and since replacement would be fairly afordable, the risk of inadvertently doing serious damage doesn't deter me as much as it might under other circumstances. So, can anybody offer advice on what to try?

Sorry to be so long-winded. I would welcome any guesses or suggestions that seem relevant.

Thanks,
q10

03-06-2008, 03:14 PM   #2
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Did you perhaps put the shim on the focusing screen on the wrong side of the screen when you replaced it? Easy to do. I had to install my new screen twice. Once wrong, once correct.
03-06-2008, 03:22 PM   #3
q10
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QuoteOriginally posted by Canada_Rockies Quote
Did you perhaps put the shim on the focusing screen on the wrong side of the screen when you replaced it? Easy to do. I had to install my new screen twice. Once wrong, once correct.
Oh - sorry, I knew I forgot to mention something. This would be the most likely explanation, however, I've tried reinstalling the screen a couple of times without any difference in results (awkwardly, I got the screen almost as soon as I got the camera, so I don't know if it had this problem before). It only really seems to fit in one way - but it's certainly possible that I'm consistently making the same error, so if you have particular advice about what signs of this problem I should be looking for, I can poke around and see if that's it. In any case, thanks for the suggestion.
03-06-2008, 03:27 PM   #4
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QuoteOriginally posted by q10 Quote
Oh - sorry, I knew I forgot to mention something. This would be the most likely explanation, however, I've tried reinstalling the screen a couple of times without any difference in results (awkwardly, I got the screen almost as soon as I got the camera, so I don't know if it had this problem before). It only really seems to fit in one way - but it's certainly possible that I'm consistently making the same error, so if you have particular advice about what signs of this problem I should be looking for, I can poke around and see if that's it. In any case, thanks for the suggestion.
There should be an instruction set available on the Pentax site. Without the pictures to guide, I would just confuse the issue for you. I put grid screens in any camera body that will accept them, so I make the change as soon as I have bought the camera, and never look again.

03-06-2008, 04:11 PM   #5
q10
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QuoteOriginally posted by Canada_Rockies Quote
There should be an instruction set available on the Pentax site. Without the pictures to guide, I would just confuse the issue for you. I put grid screens in any camera body that will accept them, so I make the change as soon as I have bought the camera, and never look again.
I couldn't find the Pentax instructions, but as best I can tell everything looks like it should in the isntructions from the screen maker here:

www.katzeyeoptics.com/files/PENTAX.PDF

Oh well, trying again can't have hurt. Thanks again.
03-08-2008, 04:43 PM   #6
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If you're handy with small tools and not afraid to mess with your camera's innards, read through this post I started - https://www.pentaxforums.com/forums/pentax-dslr-discussion/18498-two-ways-adjust-focus.html - there's links to two different ways to adjust front/back focus on the DS. Good luck.
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