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12-09-2010, 06:48 AM   #1
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Interesting "bug" found?

I recently bought the K-5 and love it, but seem to have stumbled on a "bug" and wonder if anyone else has seen this. I shoot almost exclusively with the 35mm/f2.8 Limited Macro and while on a recent trip to see family in Colorado I noticed that I am getting severe chromatic aberration with the lens-something I've never experienced before with my K20D.
The shooting conditions were as follows: overcast skies (perfect lightbox conditions, if you will!) shooting into a stand of quaking aspens in a open area OR shooting distant mountain peaks against the sky, at roughly right angles to the sun. In almost 500 shots there is clear and very strong CA showing. I was shooting wide open at f/2.8 or stopped down to f/8 in all cases. I also shoot an old Kiron 80-200/f4.5 Macro lens manually and it exhibits the same issues when shooting at all focal lengths as well.
Any suggestions, or should I call Pentax? By the way, I stopped by the "mother ship" in Golden while there and played with the 645D awhile! I am in LUST! I gotta get me one a dese! 8o)
Rob

12-09-2010, 07:01 AM   #2
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rob, can you post some of the offending shots with complete exif attached? If we can see what is wrong it is a LOT easier to find the cause and suggest solutions. Since the problem is across several different lenses it is a camera problem, but it may be something simple. But we need to see the shots first.

NaCl(my initial thought is a wrong WB setting but we need to see the shots)H2O
12-09-2010, 07:32 AM   #3
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Here's an example

Don't know if this is correctly attached, since this is the first time I've tried it, but here goes!
Rob
Attached Images
 
12-09-2010, 07:45 AM   #4
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Haven't seen your images, but it is well known that the DA35 Macro is quite prone to out of focus color fringing.

12-09-2010, 03:28 PM   #5
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Really? I've taken over 3,000 shots of mainly flowers with it on my K20D and wide open to get that sweet bokeh and can't remember more than MAYBE 20-30 with CA issues. I personally have to believe it is my unfamiliarity with a new camera (my number one suspicion), an issue with settings or a broken camera or a true bug!
But thanks for the suggestion. I continue to investigate and have asked a couple of Pentax pros to weigh in as well. I'll keep the forum advised on what I find out as soon as I get a solution. I suspect it MAY wind up being "pilot error" though! *o)
Rob
12-09-2010, 04:25 PM   #6
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Others have mentioned the K-5 has more PF than usual. I had thought it was because of a weaker AA filter (same thing they tried w/ the K10D), but sharpness isn't better than the D7000 that uses the same chip...
So you're not imagining things...someone should try a Tamron 70-300 on the K-5...it PF'd a lot more on the K10D than my current K20D :-)
12-09-2010, 05:15 PM   #7
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QuoteOriginally posted by robw Quote
Really? I've taken over 3,000 shots of mainly flowers with it on my K20D and wide open to get that sweet bokeh and can't remember more than MAYBE 20-30 with CA issues. I personally have to believe it is my unfamiliarity with a new camera (my number one suspicion), an issue with settings or a broken camera or a true bug!
But thanks for the suggestion. I continue to investigate and have asked a couple of Pentax pros to weigh in as well. I'll keep the forum advised on what I find out as soon as I get a solution. I suspect it MAY wind up being "pilot error" though! *o)
Rob
How many of those flowers were against a white sky? I don't think this is a bug but a function of the photo. There are ways to avoid it as well as fix it. I can make every lens on my list do this. The main key is you have to have the WB properly set and get the exposure right. In your sample photo type, that can be difficult of course but those two items will help reduce it.

That said, it is entirely possible that the K5 is a little more susceptible to it. I have not tried my DA35 on that camera yet. It's dark now so for me to offer any sort of compare, It's going to have to wait.

This is a photo taken of a lens I have in the marketplace. It was taken with the FA31 and is over exposed. That's what I mean by you need to get the exposure right. In this case, I did it on purpose to show the inside of the rear of the lens.

http://www.rolleiman.com/Photos/ForSale/PayforStuff/k5js1433_mK135f35__sell_takenwFA31.jpg


12-09-2010, 05:34 PM   #8
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Nice colors Jeff!

NaCl( "this is your lens on drugs!" )H2O

12-09-2010, 05:39 PM   #9
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robw,

Yes I see "some" CA but I'd hardly call it severe. Much less severe. I didn't see much when I was at work, but that's a non calibrated monitor. At home now with my calibrated monitor, and I don't see much more CA than I would expect with this type of photo.

NaCl(but maybe that is just me)H2O
12-12-2010, 08:11 AM   #10
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I have several more photos where the CA is significantly worse, but am continuing to investigate the issue and will report back to the group. As I said, I now suspect it is a combination of "pilot error" and unfamiliarity with a new camera. Regardless, I WILL let everyone know what I find out as I experiment to both replicate and overcome this CA issue.
And for Jeff, I fly against the grain there because almost 100% of my flowers are shot on location in greenhouses, using natural light and against a white background. I HATE using flash and black backgrounds for flowers is so overdone! Must work, because I have a thriving business from it! *o)
Rob
12-12-2010, 08:30 AM   #11
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QuoteOriginally posted by robw Quote
And for Jeff, I fly against the grain there because almost 100% of my flowers are shot on location in greenhouses, using natural light and against a white background. I HATE using flash and black backgrounds for flowers is so overdone! Must work, because I have a thriving business from it! *o)
Rob
Who is talking about using a flash and a black background? My point was, that Any lens can be made to exhibit CA, and I can make Any lens do it in the right conditions.

DA35 f2.8 at f2.8. No Flash, No Black Background. (K7)



Same day..




Oh, and if you want to talk about something being overdone. Negative space beach sunsets.


12-12-2010, 06:26 PM   #12
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"Oh, and if you want to talk about something being overdone. Negative space beach sunsets." Heavens YES! Thanks for THAT one!
Rob
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