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01-08-2011, 04:45 AM   #1
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K10D, Cosina M42 135mm f2.8 and purple fringing

Hi,

I have noticed a lot of purple fringing on this lens. I am shooting with a 1 1/2" lens hood and no filter.

Is this because it's an old lens, something about the K10D, or a fact of life when shooting under these conditions?

OK, I am a noob, but I would like to know what I am working with in this regard...

jpeg straight from the camera, taken wide open. Picture taken as an example, it ain't art! I got much more fringing yesterday against cloud.


Thanks.

Jez

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01-08-2011, 12:20 PM - 1 Like   #2
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You will find the purple fringe to be quite common with older lenses particularly. The PF is actually a sensor artifact rather than chromatic aberration. I use Lightroom and find the PF can be reduced to almost none by simply turning the purple down in post processing. Whatever processing program you are using should be able to do something similar. This fringing shows up mostly when there is a high contrast break.
01-08-2011, 02:19 PM   #3
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It's funny but I don't see any PF in the shot but only a little
Lateral CA
01-08-2011, 10:12 PM   #4
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QuoteOriginally posted by Lowell Goudge Quote
It's funny but I don't see any PF in the shot but only a little
Lateral CA
I did not see any either, but assumed it disappeared in the size reduction. Good catch Lowell.

01-09-2011, 03:10 AM   #5
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Thanks all for the replies. I can see what I assume is PF above and to the right of the pigeon, around the branches. I was actually trying to replicate a shot that I took the day before, which had loads of purple fringing. It was a bit over exposed, and this one it a bit under. Maybe that has made a difference.

Will google Lateral CA, and try the PP trick.
01-09-2011, 05:42 AM   #6
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I have a simple way to test lenses for PF. In a corner of my office, atop a white indented cabinet, is a brass tin-can lamp with a CF bulb sticking slightly out its top, adjacent to some figurines (articulated wooden art models). From my desk, I focus on the figurines and shoot. The resultant image also contains the lamp and the cabinet edges. After shooting, I chimp and enlarge the image. Some fringing where the CF bulb emerges from the can is tolerable, to me. Fringing on the cabinet edges is not. Some lenses show no fringing at all; with others, the fringing is thick and bright. I don't keep such lenses unless they have redeeming features.
01-09-2011, 05:58 AM   #7
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I think what you see is lateral CA. It is easy to take out in PP

Note most legacy lenses exhibit this. It was only in the 1980's that makers started with aprochromatic designs
01-09-2011, 10:08 AM   #8
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Found a great explanation of Lateral and Longitudinal CA. I include it here in case others find it useful.

Chromatic aberrations

I took some nice pictures with the Cosina today, I'll post one later. May also add to the reviews page at some point.

01-09-2011, 05:27 PM   #9
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Yep, I see the PF, but it is pretty mild and not like the great blue bloom present with some camera/lens combinations.


Steve
01-11-2011, 05:12 AM   #10
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Better photos with this lens on flickr...

Toddler's Cove - a set on Flickr


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