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05-13-2013, 05:21 PM   #1
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Lens or sensor?

I have a fairly new K-30 with a relatively old 18-55 kit lens I got with a *ist-dl a while ago. I don't have any other lenses to test with at the moment, waiting for delivery of another. I have a funny round blur about 1/4 of the way down from the top and just left of center. It looks like something out of focus, but I think if it were on the lens it would just affect the IQ not actually show up. But if it's out of focus, it can't be the sensor... Hmmm.

Would someone give their opinion on the aberration visible on the attached images of a grey sky? If you flip through them you can see it more easily.

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PENTAX K-30  Photo 
05-13-2013, 05:25 PM   #2
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I should also add that my lens looks spotless as far as I can tell, and I've done the dust removal option on the sensor. I haven't yet tried blowing air on the sensor as I don't want to risk introducing *more* dust unnecessarily.
05-13-2013, 05:30 PM   #3
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Given the fact that it seems to get worse at smaller apertures, it's probably something on your sensor. One of these should be able to get rid of it

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05-13-2013, 05:36 PM   #4
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What about a fingerprint on the rear element?

05-14-2013, 11:15 AM   #5
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I had a big greasy smear on a 28mm prime I somehow missed when I was trying to fathom why I was having issues with it once. I'd check the rear element as well before diving into the guts of your sensor to try cleaning it.
05-15-2013, 02:08 PM   #6
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The real problem is that you are confusing things by shooting against a cloudy sky, so there are a lot of changes in shades over the frame. A more uniform surface would definitely help showing the issue , BUT it almost looks like a reflection off something shiny now the lens / lens mount.
05-17-2013, 05:42 PM   #7
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Well, I think Adam wins the prize. I still don't have my new lens, so I decided to try the blower route. I don't see any evidence of the blob now. Lowell, I realize a cloudy sky isn't the best test subject, but I just moved in to a new house and couldn't find anything uniform, the sky was the easiest thing I could find in short order.

Thanks everyone for their advice!
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05-17-2013, 06:18 PM   #8
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QuoteOriginally posted by mvsjes2 Quote
Well, I think Adam wins the prize. I still don't have my new lens, so I decided to try the blower route. I don't see any evidence of the blob now. Lowell, I realize a cloudy sky isn't the best test subject, but I just moved in to a new house and couldn't find anything uniform, the sky was the easiest thing I could find in short order.
I'll usually just use my wall or the ceiling or a closeup of the refrigerator, or the stove or...

05-17-2013, 06:29 PM   #9
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Yeah, checked all that, fridge is that fake leatherette, walls are stucco, ceilings have large beams with ornate wood in between. It's an interesting challenge around here...

Attached is the pic that made me notice.
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