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04-17-2016, 03:15 AM   #1
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Pentax 100mm 2.8 lost it's sharpness

Hello,
I have recently noticed that my lens Pentax 100mm 2.8 lost its sharpness. I use this lens with Pentax K-3.
I have been using this lens for about 6-7 years, it has never been dropped or damaged. Mostly I work with f 2.8.
Perhaps someone faced this problem and I wonder, if this could be fixed?
Thank you for your answers.
I am adding some photos. I think the problem is not with front or back focus, it's just very unsharp pictures, I tried to focus with auto and manual settings - problem still remains.

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04-17-2016, 03:28 AM   #2
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Have you tried to take a look inside?
100/4 were affected by cement separation AFAICR, don't know about 100/2.8...
Might be anything though, from a loose/displaced element to fungus etc.
04-17-2016, 03:29 AM   #3
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hmmm curious. Shine a bright light through the lens and look for haze. But, perhaps, it is simply an AF issue. Try adjusting AF through fine adjustment to test for front/back focus issue.
04-17-2016, 03:53 AM   #4
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Looks like affected by smeared with finger grease rear element of the lens. Have you tried to clean the outer lenses?

04-17-2016, 04:04 AM   #5
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Looking from outside - no fungus, no haze. Yes, I tried cleaning both sides of the lens.
I guess I will try to test for front/back focus and to bring it to repair.. :/
Thank you for your answers.
04-17-2016, 05:22 AM   #6
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Try using live view and see if the focus is better.
04-17-2016, 05:56 AM   #7
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How long have you been using it with a K3? If a while, was it once ok with the K3?
04-17-2016, 06:00 AM   #8
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QuoteOriginally posted by JohnX Quote
How long have you been using it with a K3? If a while, was it once ok with the K3?
With K-3 I have been using for about 1,5 year. Only few months ago I noticed sharpness issues.

04-17-2016, 07:14 AM   #9
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Which 100 2.8 is it?
04-17-2016, 08:01 AM   #10
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QuoteOriginally posted by UncleVanya Quote
Which 100 2.8 is it?
EXIF shows PENTAX-D FA Macro 100mm F2.8 WR.
04-17-2016, 08:36 AM   #11
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F 2.8 and focus distance close. Depending upon how close that focal range could be pretty small.....7/10 of a millimeter at 1:1
The slightest breeze will move your subject in and out of focus......
How do photos shot a bit more closed look?
04-17-2016, 09:44 AM - 1 Like   #12
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QuoteOriginally posted by Mistlefoot Quote
F 2.8 and focus distance close. Depending upon how close that focal range could be pretty small.....7/10 of a millimeter at 1:1
The slightest breeze will move your subject in and out of focus......
How do photos shot a bit more closed look?
Another way to check for sharpness vs bad focus is to take a picture of a textured surface or a page of text at an angle, with focus somewhere near the middle. That way some part of the subject will always be at critical focus, and you can see how sharply that renders. If it looks sharp, the issue is focus; if not, there's something wrong with the lens.
04-17-2016, 12:41 PM   #13
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I had a major problem with a few different lens cleaning solutions. Grease impregnated Wipes and pads (Brand new ones at that) that utterly coated my lenses. Actually ended up with a (Very small) scratch on my 85mm 1.9 from them, and took about six days to figure out that that was my issue. They looked clean until you looked from the side, then you saw the grease streaks across the glass.

Looked about the same as your problem. I'd say go get some fresh cleaning stuff and try again?
04-18-2016, 12:40 PM   #14
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QuoteOriginally posted by Precious Quote
I have been using this lens for about 6-7 years,
If OP has been using this lens for so long, mostly at f2.8, as stated, then OP probably already knows about how shallow DoF is in macro range, especially at apertures wider than f5. And OP probably knows that no lens is optimally sharp wide open. So, sure, it is possible that OP is having problems with shallow DoF (which could be further connected to misfocusing), or that OP has expectations too high, but after 6 years of use? They probably have a good idea of what that lens delivers.
I see OP already checked for smudges on the front or back element.
Make sure there is no filter mounted. Check the mount and barrel for any signs of damage. The 100mm macro is an amazing lens, it is odd that it would develop a problem. But lenses can get damaged over time, especially if they are used very intensely.
Another thing to look at is PP - have you maybe changed jpeg options or lens profiles? Started using another PP software?
You might want to take it to a specialized repair shop and have them look at it. They usually charge a certain flat rate to just look at your lens and give you a quote on what actual repairs would cost. Hope you get it sorted out.
04-21-2016, 12:19 AM   #15
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Thank you for your comments. I will try to clean it once more and probably bring to the specialized repair shop. I love this lens because of it's sharpness, mostly used in macro photography, and it is very pity to loose one of it's best features.
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