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04-22-2010, 05:28 AM   #1
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FA 31mm what's wromg with my lens??? please please help

just brought this AIS (Australia - CRK) a couple of weeks ago had major problems adjusting the AF focus for close ups ie flowers (+70 on my KX) but now my landscape photos are just crap!!!!!!!!!!! I can get better images with my FA 50mm wide open. Below is a crop on where the focus should be plus a link to the full size photo. Is this an out of focus photo or just a bad lens?

Please help I bought this lens for my holidays in a few weeks and have no idea about why these photos are poor quality. (with all my lens I do a focus test on a focus chart then brick wall tests all with great results... except of course the only lens I really don't need but just had to get! (perhaps this a cure for LBA...)



full size image link...
http://phreddy.zenfolio.com/img/v7/p1023242447.jpg

another full size image link
http://phreddy.zenfolio.com/img/v9/p804412874.jpg

To be honest I am at my wits end about this lens so any comments suggestions would be most welcome.

04-22-2010, 05:37 AM   #2
axl
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I would say it's front focused.
To my eye the focus is actually just below the road below the boat.

BR
Peter
04-22-2010, 05:44 AM   #3
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Are you using a filter?
Sometimes filters can degrade the image quality.

I see these are at f/2.4 and f/1.8, so focus is pretty critical too, but I really can't tell where the focus is in the first one. The second shot appears pretty close, but at 1.8 the depth of field is pretty thin so you could be a touch in front and it'll screw up the whole image.

Good luck with it!
04-22-2010, 06:08 AM   #4
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QuoteOriginally posted by farfisa Quote
Are you using a filter?
Sometimes filters can degrade the image quality.

I see these are at f/2.4 and f/1.8, so focus is pretty critical too, but I really can't tell where the focus is in the first one. The second shot appears pretty close, but at 1.8 the depth of field is pretty thin so you could be a touch in front and it'll screw up the whole image.

Good luck with it!
I don't think it's a filter.
In the second shot the focus appears to be just in front of the twigs on the mall.

Basing on those two shots, I believe his lens does front focus....

04-22-2010, 06:53 AM   #5
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It is difficult to determine the problem (if any) based on those shots. For focal length 31mm at f4 aperture the hyperfocal length is about 40 feet. Focus on any objects beyond the hyperfocal length - you should be able to determine if the focussed object is sharp or not (ff or bf).
04-22-2010, 07:53 AM   #6
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I'm not seeing anything in focus in either shot.. Have you tried turning off the AF and going manual focus just to determine it is Not the lens? You say you adjusted the AF +70 for doing Closeups of flowers. What happened with the Rest of your lenses? Does the Kx support AF adjustment or did you use a hack?

04-22-2010, 08:34 AM   #7
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QuoteOriginally posted by JeffJS Quote
I'm not seeing anything in focus in either shot.. Have you tried turning off the AF and going manual focus just to determine it is Not the lens? You say you adjusted the AF +70 for doing Closeups of flowers. What happened with the Rest of your lenses? Does the Kx support AF adjustment or did you use a hack?

Sounds to me like he used a hack to get the lens to focus closer than it's natural minimum and now it won't focus to infinity in AF.
Just a guess.
04-22-2010, 09:09 AM   #8
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Something is wrong in both shots.

I'd test it again by shooting along a brick wall or something with an identifiable focus spot to see where it is actually focusing.

04-22-2010, 09:40 AM   #9
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QuoteOriginally posted by Parallax Quote
Sounds to me like he used a hack to get the lens to focus closer than it's natural minimum and now it won't focus to infinity in AF.
Just a guess.
You're probably right and that's why I asked if the lens can be focused without the AF getting in the way.. FWIW, I think AF is really a poor way to Test a Lens for sharpness. Turn off the AF and see if the lens can be focused and give a sharp photo At All. THEN give the best calibration possible (which should be done at a moderate distance).

04-22-2010, 09:51 AM   #10
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Arh, I didn't read the OP carefully, if anything at all, try to undo what have been done before, reverse the +70 focus adjustment and see if that help. It almost sounds like something similar to putting on extension tube and not adjusting to the focusing distance.

Just curious about the focus adjustment, is the adjustment on a per lens base or for every lenses?
04-22-2010, 12:34 PM   #11
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Also what settings have you for AF?

Seems to be front focusing
04-22-2010, 03:41 PM   #12
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QuoteOriginally posted by pHREDD D Quote
I can get better images with my FA 50mm wide open. Below is a crop on where the focus should be plus a link to the full size photo. Is this an out of focus photo or just a bad lens?

To be honest I am at my wits end about this lens so any comments suggestions would be most welcome.
You pretty much experience what I went through with my first 31mm Limited when I got it in August 2009. Lens was one of the first "Assembled in Vietnam" series.

When I posted my findings most of the people here said that I'm wrong or it's a matter of back or front focusing.

Nevertheless I returned it to B&H Photovideo and requested an exchange for one "Made in Japan". When it arrived I could finally see why people say this lens is sharp even wideopen.

With time many people on the forum started experiencing the same issue with 31mm Limited lenses "Assembled in Vietnam". I personally know two forum members in Melbourne who had the same problem.

If you can contact CRK and ask them to send it back to Japan for adjustment as it appears that the lens has a decentered optics.

The lens is great and is a keeper. If nothing works, sell it and buy a mint second hand made in Japan.

Good luck.

Last edited by Voe; 04-22-2010 at 03:48 PM.
04-23-2010, 12:46 AM   #13
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thanks Voe.

I've reset the AF adjustment - taken more landscape and portrait photos and wide open they are the worse quality I have ever seen. Looks like this lens won't be going on holidays next month...
04-23-2010, 01:42 AM   #14
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QuoteOriginally posted by pHREDD D Quote
you can look up at flickr how your photos should look like Kx + 31mm
31mm - Flickr: Search

in the first one the focus is on the grass in the front
but the second one doesn't look like front focus

both photos are way too soft
and it produces massiv green edges - this should not be like this

i personally found the 31 is not the "magic best off all super lens" as a lot of people
think of it - maybe it is, because even the standard-lenses are allready quite good

but it is a very good lens - resolution is very high, bokeh is outstanding and the colours are great

test it with different settings on one shot - starting with "auto" and than move on with manual settings
if the results all look that bad send it back
04-23-2010, 02:19 AM   #15
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Totally unexpected from a lens of this class.
My own copy is absolutely stellar in performance and has an HMC in front of it without any noticeable effect.

Mate, get it looked into with another camera and see if it's an intrinsic lens problem or some focusing issue between the lens and camera.
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