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10-04-2009, 08:32 PM   #1
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purple haze? what could be the cause

Took this pic this afternoon (cropped) and found a purple haze outlining the bird. Sun was to the left side. Any ideas as to what caused the purple outline?



10-04-2009, 08:44 PM   #2
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It's called chromatic aberration, and it's caused by your lens. It's usually a symptom of a crappy lens, but it happens with a lot of lenses, even good ones, if you have your aperture all the way open or all the way closed.
10-04-2009, 08:44 PM   #3
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A case of strong CA of a purple shift (PF) exacerbated by haze/softness (being slightly out of focus).
It is more pronounced with some lenses on digital cameras.
Beyond that, I'd be referring to the optical specialists on the forum...

edit - beaten to it...
sorry for repeating the answer...
10-04-2009, 08:45 PM   #4
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it's called CA (chromatic aberration) and it can be caused by lens's and digital sensors. It's inherent to some degree in almost every digital sensor I have ever seen.

Lower optical quality lenses suffer from it more than higher quality lenses.

Here is a link with more info:

Chromatic Aberration - Wikipedia


EDIT: WOW, me too

10-04-2009, 09:13 PM   #5
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Did a quick check of the lens reviews for this lens and I see CA is a common "con" in the reviews:



PentaxForums.com Third-Party Pentax Lens Review Database - AF 70-300mm F/4-5.6 Di LD MACRO 1:2

shot was taken at 300mm, f/8.

Thanks to all for the help.

Last edited by JimD_K10D; 10-04-2009 at 09:31 PM.
10-04-2009, 09:51 PM   #6
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That lens is known for the "pruple fringe". But, for the price it is a great lens. Very sharp.

To reduce the fringe, stop the lens down to f11 or so. Try to shoot lower contrast scenes, and learn to remove the fringe with software.

I thought I had read that the Tamrom 70-300 DI LD fringes less on the K20D then it does on teh K10D. If anyone knows, I'd be interested.
10-05-2009, 08:20 AM   #7
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Yep, I recognized the lens instantly from the extreme purple fringing. Doesn't show up in all pictures, but when it does, it's as bad as I've ever seen from any lens, and that's the case here.
10-05-2009, 08:27 AM   #8
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When I saw the thread title, I thought this was something completely different. "Purple Haze" is something I only worry about if the cops are anywhere nearby

Anyway the answers above have it covered. The common term is PF or Purple Fringing.

10-05-2009, 11:38 AM   #9
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I suggest that we call it purple haze instead of purple fringing from now on (and I'm being kind of serious).
10-05-2009, 12:20 PM   #10
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QuoteOriginally posted by JimD_K10D Quote
Took this pic this afternoon (cropped) and found a purple haze outlining the bird. Sun was to the left side. Any ideas as to what caused the purple outline?
Don't worry about it. That bird is the "Purple Fringed Gourlet"..... they all have that purple fringing.
10-05-2009, 12:44 PM   #11
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Sad thing about PF/CA, is that once you see it... you will always see it.

The story above about it being a problem with inexpensive lenses is sadly not true... Many of our famous, very expensive Prime Pentax lenses suffer from PF...

None as bad as the Tammy 70-300 though. It is a fine lens in non contrasty situations and I have some good shots taken with it. But many with bad PF also.
10-05-2009, 01:43 PM   #12
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What people haven't mentioned yet is that you are able to remove it slightly in you photo editor. Camera RAW in Photoshop for example has one of these functions and if you took a jpg then the function is hidden in Filter - Distort - Lens correction
I use this function alot and I've only seen pictures get better if you use it moderately.
10-05-2009, 01:46 PM   #13
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Good point... I think you should send Stardust the original size file and let them do their magic on it... There are a few PF fix programs around.
10-05-2009, 02:17 PM   #14
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Funny thing. As soon as I saw the picture, word "Tamron 70-300" popped up in my head

edit: Oh..I see I'm not the only one
10-05-2009, 04:14 PM   #15
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QuoteOriginally posted by Igilligan Quote
Many of our famous, very expensive Prime Pentax lenses suffer from PF...
PF = Pentax Fringing.
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