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02-27-2009, 05:08 AM   #1
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something puzzles me with new K20D

Hi folks,

one of my first posts here and I hope that you can help me understand if I need
to see an optician, or if maybe what I am seeing is really there...

Last three years I have been using K100D, am very happy with it and
quite recently I bought a K20D looking for more resolution and a camera
with better ergonomics.

Today I tried some test pics with FA* 200mm and I think I am seeing a
strange "sharpness pattern" that I am not able to understand.
Please have my apologies for yet another boring brick wall picture.

If you click on this link you will see a full size out-of-camera JPEG

The picture is taken from a tripod (a sturdy one I would say) with SR disabled
and 2s timer with mirror lookup @ F8

Can you see some sort of "wavy" pattern when it comes to sharpness?

It should be noted that it is not taken through a window glass, and building
is far enough to exclude variations because of DOF.

If you do see it, do you have an explanation what could cause it?
In my view it can only be the sensor.

Have to say that I have not noticed any problems with same lens on K100D
but K20D is different animal alltogether...

Many thanks in advance for all advice,
Samir

02-28-2009, 12:27 PM   #2
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Hello,

just wanted to add that I think that I can see same thing with DA 55-200:


full size JPEG

what am referring to are unsharp areas that are spread across the picture with
sharper areas in between

lens defects are usually shown on one side, at corners or all across the whole frame so that
makes me believe it is not lenses, but on the other hand I am not able to detect the same
thing with 77mm limited...?

All comments and advice are appreciated,
samir
02-28-2009, 12:48 PM   #3
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I see a little about what you are talking about. It might be helpful to shoot something like a newspaper to see if it is consistent.
02-28-2009, 01:02 PM   #4
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QuoteOriginally posted by samir_m Quote
Hello,

just wanted to add that I think that I can see same thing with DA 55-200:


full size JPEG

what am referring to are unsharp areas that are spread across the picture with
sharper areas in between

lens defects are usually shown on one side, at corners or all across the whole frame so that
makes me believe it is not lenses, but on the other hand I am not able to detect the same
thing with 77mm limited...?

All comments and advice are appreciated,
samir

I believe I see what you are referring to (esp. on right side of photo in the bricks). However, this is definitely not the camera. If I am forced to guess, I am certain this is a lens smudge or perhaps even (nearly invisible) fungus inside one or more of the lens elements.

BTW, your example is, at least, 1 stop underexposed.

02-28-2009, 01:23 PM   #5
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you can see it as well, ok it is not just me, am still not sure how much effect this will have
in real life and real pictures, but if camera or lens(es) is somehow faulty I would like to fix it
...pixel peeper's curse ;-)

Presto: have tried with different patterns on LCD monitor from much shorter distance, but
can not see the same thing, will try with a newspaper tomorrow in daylight

pentaxmz:
that were my thoughts at first , but if it is lens smudge or fungus, how likely is to have it with
two different lenses?!? on the other hand have not seen it with FA 77mm and sigma 17-70
but honestly have not peeped that much with those two... btw cannot see any fungus,
and there are maybe two dust particles in FA*, but that should not have such effect methinks
regarding the exposure, it was camera metering, have not done any compensation and
JPEGs are straight from camera, no processing

thank you for you comments
02-28-2009, 01:31 PM   #6
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Yes, I see something like smudge or fuzzy sharpness on the right side of your picture.
Since it doesn't appear on other lens, have you checked inside your FA* 200?
maybe you can take it off and look from behind the glass with different distance against a light.
That's how I found something wrong with my other lens before.
But be very patient since it might be something thin that is not easily noticed.
02-28-2009, 01:34 PM   #7
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thanks Herman, ok will check it again, not sure if it is clear from my previous posts, but

this is picture taken with FA* 200mm and

this one is taken with DA55-200 @ 200mm

both pictures straight out of camera no pp-ing
02-28-2009, 02:16 PM   #8
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I'm inclined to say that it's the camera. If you've used these lenses on the K100D with no problem, and both lenses now show this pattern on your K20D, it must be the camera.

02-28-2009, 03:15 PM   #9
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I see not only the right side but also on the left side; I also think it is the camera not the lens (chance of smudges or fungus on both lenses is small). If it is under warranty - I would take it in for repair right away.
02-28-2009, 03:30 PM   #10
Dan
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After looking at the full-size image, I would say the following:

(1) The FA*200 is a very sharp lens.

(2) There seems to be smudges of some sort on the AA filter covering the sensor.

It may be possible to clean it. I would take a look to see if there is any obvious contamination. If you do decide to clean it yourself, be very careful or else you may make it worse. Unless you have some experience with this sort of thing, a visit to a service center may be in order.

Dan
02-28-2009, 03:46 PM   #11
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wavy

If you have any filters mounted on the lens, remove them. Try to duplicate the same conditions again and repeat your examples. Filters and digital lenses do not always play nice.
Jim
02-28-2009, 03:51 PM   #12
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thanks folks, appreaciate your advice

have not inspected the sensor, but will do it

do you think it would be safe to use "copper hill" method with clean ethyl alcohol on
K20D sensor? maybe it safest to send it back, had it only about a month...

regarding filters, have Sigma EX UV filter 'permanently' on FA*, tried without it and it still looks the same...
02-28-2009, 05:55 PM   #13
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I'd say it's almost certainly either a dirty or defective AA filter. Defective is unlikely given how expensive those dang little pieces of glass are, they're so pricey because they have to be perfect each time. Dirty is more likely. idk, I wouldn't clean it myself. If it came like that, and if it's under warranty in particular, then Pentax should repair/clean it.
03-01-2009, 02:05 AM   #14
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inspected the sensor and can not see anything strange, but then if there is some
contamination or defect it is probably not visible to a naked eye

was thinking that it might be 'atmospheric' or caused by warm air going out through
my balcony (a long shot probably)

tried some pictures indors but the problem is that at closer ranges it is hard to get camera
plane parallel to the subject and at 200mm DOF becomes an issue
maybe I'll just take a risk to be seen as a weirdo in the neighborhood and go out with tripod
to take some brick wall pics...
03-01-2009, 02:45 AM   #15
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Check if the fuzzy areas are on the exact same spot on all pictures. Then you know if it is on the sensor or not.
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