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12-13-2012, 05:10 PM   #1
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Bought a used FA 31... some issues..user or lens?

Hi. I just bought a used FA 31 limited from ebay in the UK. I noticed some strange focusing issues when i took it out today on my K5, in that it would focus on another area other than that which i had selected and was pointing to. The light was fading when i got a chance to get out so i didn't get to test it properly in good light unfortunately. I have added some shots below which should show what i was experiencing. When i tried it at home under tungsten light, accuracy was way off but i know the K5 classic isn't meant to be great in this respect, however i have never seen such far out results even in this type of environment. What really boggled my mind was when i took out my FA 43 and Da 35mm macro and found i was experiencing the same sort of problems. I have never had back focus or front focus problems before and i don't know i am sending myself insane. Doing this in daylight would make life a lot easier to test this properly. I have done some very low light shots with both my FA 43 and DA 35mm macro recently and they were perfectly fine. I completely understand that user error is possible here and none of my test are scientific, it's just that i haven't had these type of issues before. I shot these all wide open.

I printed out a focus chart from the web although i am not sure if i was using it correctly. When i aimed at the center at a 45 degree angle on a tripod and using a two second delay it was spot on where i aimed it at every time.



With this first shot, i tried numerous times to get the post in focus with no success. Some other part of the image would be in focus each time.



Another example of where i was aiming at the text in the sign and the trees above were in focus instead.



This was a shot of my dog and i was repeatedly getting areas around her in focus and not herself. This was obviously in poor lighting so this may not count as much.

Any help is much appreciated!

12-13-2012, 05:14 PM   #2
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Here are instructions for using the chart:
Fixing Front and Back Focus - Introduction - PentaxForums.com

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12-13-2012, 05:29 PM   #3
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You seem to have chosen really difficult conditions for any lens.

Vertical lines will usually cause trouble, add low light and its double trouble.

Since you have the same problem with 3 lenses, see what happens in better light and without all those lines in the background...
12-13-2012, 05:33 PM   #4
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Thanks for that Adam and i definitely want to get it and do this calibration properly. The thing i am wondering is if the lens i bought used is best sent back soon as getting the calibration unit shipped might take a while. I am probably worrying too much and no doubt this would fix it but i noticed mention of cases where it cane be so far out that using this calibration mightn't be sufficient in some cases.

12-13-2012, 05:35 PM   #5
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Yeah Psyhdoc i will definitely try again in good light tomorrow and with less challenging focus situations. Thanks.
12-13-2012, 05:38 PM   #6
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Check your AF settings - you may have set the camera to do spot focus somewhere away from the centre of the scene. Set the camera to centre-spot AF and try again.

Also note the following from Nikon about AF:

12-13-2012, 05:44 PM   #7
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Thank you Rawr. I pretty much used center focus for most of the shots. I did check my AF settings and noticed that the shutter was set to release even if the shot was not in focus so maybe that would help. Cheers for that page too!
12-13-2012, 05:47 PM   #8
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QuoteOriginally posted by captainbert Quote
Thanks for that Adam and i definitely want to get it and do this calibration properly. The thing i am wondering is if the lens i bought used is best sent back soon as getting the calibration unit shipped might take a while. I am probably worrying too much and no doubt this would fix it but i noticed mention of cases where it cane be so far out that using this calibration mightn't be sufficient in some cases.
Try using this to test your lens using the same methods as described in the article:
http://www.k10dbook.com/newchart.pdf

If AF adjustments end up being insufficient, send the lens back.


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12-13-2012, 05:51 PM   #9
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Thanks for that Adam!
12-13-2012, 06:00 PM   #10
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QuoteOriginally posted by captainbert Quote
the shutter was set to release even if the shot was not in focus so maybe that would help.
Aha. That quite probably may be part of the issue.
Keep an eye on that green hexagon in the viewfinder at all times!
12-13-2012, 06:30 PM   #11
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QuoteOriginally posted by rawr Quote
Aha. That quite probably may be part of the issue.
Keep an eye on that green hexagon in the viewfinder at all times!
Yeah hopefully so. Thanks Rawr!
12-13-2012, 07:21 PM   #12
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You could also try to focus using liveview to see if it behaves the same or not (CDAF is usually more precise).
12-13-2012, 10:15 PM   #13
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This can definitely be a problem that shows up when you put an FA31 on a K-5 - I'm speaking from experience here. It may have been a problem with your other lenses, but for some reason it's so much more noticeable with the FA31. I think the defining characteristic of the FA31 is that it's difficult to tell exactly where in a scene (that is, at what depth) a subject goes from being in-focus to out-of-focus. It's a wonderful characteristic that few lenses can achieve, but somehow when the focus is off it seems to exacerbate the problem, and your photos come out worse than they would with any other lens.

Imagine what happens with this lens when it is front-focusing. Since your subject is commonly in the foreground, everything in the shot is out of focus! It will make you think the lens isn't sharp, when in reality it's transitioning from a vague fuzziness into the normal background blur. The point is this lens is more demanding than usual of both the camera and you, so you don't want the focus off in either direction. Try to get it right on this copy, but if you can't, send it back.

I'd say it's just as likely it's your camera as your lens, but obviously make sure the lens is OK or return it. Do your best with the adjustment charts, and then make your final decision based on real-world shooting.


I recently learned of an inexpensive adjustment solution you can try right away, without waiting for a product to be shipped to you: FocusTune

I already have the LensAlign from Michael Tapes Design, so I haven't tried this software solution, but it looks good!
12-14-2012, 11:19 AM   #14
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QuoteOriginally posted by NickLarsson Quote
You could also try to focus using liveview to see if it behaves the same or not (CDAF is usually more precise).
Yeah i did that last night and it yielded sharper results for sure but today i found the results were generally better all round apart from with a few cases which could well be me and what i was trying to do rather than the lens or camera. Thanks Nick!
12-14-2012, 11:23 AM   #15
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QuoteOriginally posted by DSims Quote
This can definitely be a problem that shows up when you put an FA31 on a K-5 - I'm speaking from experience here. It may have been a problem with your other lenses, but for some reason it's so much more noticeable with the FA31. I think the defining characteristic of the FA31 is that it's difficult to tell exactly where in a scene (that is, at what depth) a subject goes from being in-focus to out-of-focus. It's a wonderful characteristic that few lenses can achieve, but somehow when the focus is off it seems to exacerbate the problem, and your photos come out worse than they would with any other lens.

Imagine what happens with this lens when it is front-focusing. Since your subject is commonly in the foreground, everything in the shot is out of focus! It will make you think the lens isn't sharp, when in reality it's transitioning from a vague fuzziness into the normal background blur. The point is this lens is more demanding than usual of both the camera and you, so you don't want the focus off in either direction. Try to get it right on this copy, but if you can't, send it back.

I'd say it's just as likely it's your camera as your lens, but obviously make sure the lens is OK or return it. Do your best with the adjustment charts, and then make your final decision based on real-world shooting.


I recently learned of an inexpensive adjustment solution you can try right away, without waiting for a product to be shipped to you: FocusTune

I already have the LensAlign from Michael Tapes Design, so I haven't tried this software solution, but it looks good!
Thank you for that! That is very interesting what you said there in regards to the FA 31. I am going to try the focus chart you suggested this weekend. I actually had much more success today and for sure the lens is very sharp and the rendering is stunning. Maybe i am just being paranoid and my inexperience is more to blame than anything. I definitely dont want to send the lens back as i got it for a good price with warranty still remaining which would be very hard to get again! Cheers DSims!
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