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11-21-2009, 10:24 PM - 1 Like   #1
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FA31 problem maybe.. what do you think?

OK I decided to resort to test charts to compare my new Vietnam FA31 and James's older Japan FA31.. Well there is a difference for sure at f1.8, though I first notices a problem in realword outdoor shots at around f8 at distances of around 4 meters, but I haven't been able to reliably reproduce that.. still trying..

BUT at f1.8 I can show a difference. Now to get optimal focus his needs no AF adjustment, mine needs -6... These shots were taken on a tripod with cable release..

Would you return over this difference or am I being too picky? It is a very expensive lens and I expect equal quality to his one..

http://www.eisner.id.au/images/Vietnam.JPG

http://www.eisner.id.au/images/Japan.JPG

11-21-2009, 11:04 PM   #2
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I would return Joele

mate where did you purchase from?

Regards

Neil
11-22-2009, 09:11 AM   #3
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You may as well return it, you've already decided it is defective.
I do wonder about the sanity of trying to create problems, but that's your business not mine.
Are you quite certain that you are focusing accurately? I've found the best way to test for sharpness on a test target (something I rarely bother with) is to manually focus and then do a focus ring around. These little viewfinders are a PITA to manually focus with and Pentax AF is not especially accurate with fast lenses.
11-22-2009, 10:12 AM   #4
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If you are autofocusing, be sure you have the camera set to center focus. Other focusing modes may try to get the basket in focus also. The exposure looks like it is about an fstop brighter on your lens and this can affect contrast. Try matching exposures if you are going to do an A-B comparison.

11-22-2009, 01:08 PM   #5
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QuoteOriginally posted by Wheatfield Quote
You may as well return it, you've already decided it is defective.
I do wonder about the sanity of trying to create problems, but that's your business not mine.
fair enough, the reason I was trying to 'create' (find) the problem is when I use it for real world shots I get a strangely high number of shots that are just soft. Was mainly pics of people at f5.6 - f8 with pretty high shutter speeds as it was a bright day and these were outdoor shots.. I wanted to reproduce that so it was easier to return, but can't seem to do it with the test charts..

QuoteOriginally posted by pentaxman Quote
If you are autofocusing, be sure you have the camera set to center focus.
Yeah it was, I will try again matching the exposure.. ;-0


I just wish I could reproduce the real world problem.. I don't think it is the camera (which is also new) as the DA70 is 100% spot on.. At infinity or near to it the FA31 is stunning, it was just closer shots 2-5m that it was very inconsistant regardless of being stopped down.

Last edited by joele; 11-22-2009 at 01:17 PM.
11-22-2009, 01:16 PM   #6
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Agreed Joel.
Test chart results aren't everything - neither is normal everyday real world results totally reassuring.
If you find an obvious problem at any aperture, under any conditions, not in keeping with what's expected from a good copy, it's worth returning.

Did you buy from B&H? Their returns policy is excellent with regards to subpar lenses.
11-22-2009, 02:25 PM   #7
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no I bought locally, so can return to CRK for repair/checking, I'm just concened that in a 'lab' they won't confirm the problem, hence I was trying to find/reproduce it under controlled condiditons..
11-22-2009, 03:42 PM   #8
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Hopefully they don't try to prove you wrong to avoid having to replace the lens - with such subjective criteria, they may well say there's no problem with it and make you keep it even if you say you can tell the difference.

11-22-2009, 04:19 PM   #9
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yeah thats why I wanted a reproducable thing (test charts) not just a feeling that it seems too soft using it in normal use..

Anyway they emailed me back today and said they will test it for me, so best to give them the benefit of the doubt and see what they find..
11-22-2009, 04:27 PM   #10
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Keep us posted mate.
Hope it works out good for you.
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