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02-22-2010, 09:01 PM   #1
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31Ltd on its way to Japan

I have never been happy with my 31ltd, I just can't get consistant results from it.. I may dial in +6 AF compensation and be pretty happy with it and then a month later the best results seem to be with -5 AF compensation..

Now CRK have told me that is impossible, AF can't move back and forward like that! has anyone seen something like that before? can the AF compensation depend on the distance to the subject? or can it shift at all?

They did admit the lens has BF/FF issues in their test system, though most lenses did since the film days you just couldn't prove it (notice it without digital and 100%).. They said they can adjust my camera and lens combo (means adjust my camera) so they work together, but then of course if I get a new body I am back to square one.

But it does bother me to borrow Roentarre's copy of this lens and notice a real difference in consistancy of in focus shots when I spend a day shooting with it.. Same with my 50/1.4 and 35/2 they are/were always reliable, but the 31 just drives me nuts as it costs so much more I don't expect for it to have problems they do not.

Hopefully they find the cause in Japan, and/or can cailbrate it correctly without having to adjust the body to suit it..

/rant... as you can guess I just got off the phone with them, and needed to get that out of my system.. LOL

02-22-2010, 10:59 PM   #2
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Good luck, I hope they get it sorted.

I do not believe that focus can shift that much (under identical environmental circumstances) so I agree with CRK on that; I however doubt that this is something that can be fixed by calibrating the camera/lens combo.

I love to have the opportunity to compare my FA31LTD with someone else's on both my K10D and on another body. Problem is that "they" say that my FA31LTD is the only one in the country
02-22-2010, 11:03 PM   #3
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That is quite bizarre, Joel.

As you know, I have the FA31 and it was always a consistant small amount of BF on my previous bodies, *ist D, K10D and K20D. It was great when the AF adjustment feature arrived on the K20D as I could adjust it by +1 and it was fine and same now with the K-7.
02-22-2010, 11:20 PM   #4
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Perhaps something is not quite meshing up properly in the AF mechanism in the lens?

02-22-2010, 11:21 PM   #5
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Of all the Pentax primes I have, the FA31 is the only one with inconsistent AF. Even with the best possible situations, my own tests revealed the focus being achieved would shifted quite a bit in random pattern. But this has nothing to do with the regular FF/BF, it is simply inconsistent. I too was surprised because this lens is optically sharp.
02-22-2010, 11:42 PM   #6
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QuoteOriginally posted by wlachan Quote
Of all the Pentax primes I have, the FA31 is the only one with inconsistent AF. Even with the best possible situations, my own tests revealed the focus being achieved would shifted quite a bit in random pattern. But this has nothing to do with the regular FF/BF, it is simply inconsistent. I too was surprised because this lens is optically sharp.
Hmmm, I have this same inconsistency with the FA 50 f/1.4 on my K20D. I've relied on manual focus pretty much since the day I got it when I want my shots to be perfect; I simply can't trust the AF in most situations.
02-23-2010, 12:40 AM   #7
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QuoteOriginally posted by joele Quote
I have never been happy with my 31ltd, I just can't get consistant results from it.. I may dial in +6 AF compensation and be pretty happy with it and then a month later the best results seem to be with -5 AF compensation..

Now CRK have told me that is impossible, AF can't move back and forward like that! has anyone seen something like that before? can the AF compensation depend on the distance to the subject? or can it shift at all?

They did admit the lens has BF/FF issues in their test system, though most lenses did since the film days you just couldn't prove it (notice it without digital and 100%).. They said they can adjust my camera and lens combo (means adjust my camera) so they work together, but then of course if I get a new body I am back to square one.

But it does bother me to borrow Roentarre's copy of this lens and notice a real difference in consistancy of in focus shots when I spend a day shooting with it.. Same with my 50/1.4 and 35/2 they are/were always reliable, but the 31 just drives me nuts as it costs so much more I don't expect for it to have problems they do not.

Hopefully they find the cause in Japan, and/or can cailbrate it correctly without having to adjust the body to suit it..

/rant... as you can guess I just got off the phone with them, and needed to get that out of my system.. LOL
Good luck Joele and let us know the results mate

cheers

Neil
02-23-2010, 01:18 AM   #8
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Original Poster
Thanks guys, it is frustrating as the results I get with it are so inconsistant, and I know you can get fantastic copies of this lens as I have borrowed roentarre's before and his is very consistant..

They said 4-6 week turnaround for Japan, thats fine by me, I just hope they techs in Japan have more luck finding what is actually wrong with it..

02-23-2010, 06:50 AM   #9
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I have similar problem, but not that much.

good luck.
02-23-2010, 11:21 AM   #10
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I have similar experiences with some of my lenses. DA40 was so so, 43 was +200um (K10D) and now it needs +150 while 31 used to be OK on 90, then 130 and now 150 oh well, I'm so glad I got MF 24&55, don't need to focus 10mm and I'm getting close to good/very good with MFing my FA ltds.....

Good luck to getting it sorted
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