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02-17-2011, 04:21 AM   #1
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Purple fringes with K5 + DA 18-135

Hi!

Quite often I have purple fringes in my photos, meanwhiles I was told that this is no problem of the K5 but a problem of the DA 18-135. I add two photos, one where you can see windows with purple, even green fringes. The second one has purple fringes at the corner of an hut and in the branches of an tree - but I must not explain, it is quite obvious.

I am taking my photos in RAW (unfortunately except the photo of the hut), until now I used DxO to develop the RAW-files .Since quite often the photos get worse with this software I take now the Pentax Utility, maybe I will buy Lightroom later.

Is there anybody who has similar problems with the DA 18-135?

Best wishes, thanks for your help ... Josef

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02-17-2011, 05:56 AM   #2
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Hi,

what you observe is in fact chromatic aberrations (CA) and it is indeed a property of the lens, not the sensor. It's one of the types of aberrations that cannot be fully avoided with any optical setup.

Honestly, by looking at your pictures (where you created some strong contrast areas) I am impressed by the performance of the 18-135, I was expecting much worse results.

Modern softwares can help remove CA when they see it, by realigning the various colours channels (CA is caused by different colours being focused at different spots). But I wouldn't worry based on your two samples.
02-17-2011, 10:08 AM   #3
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Agree with bdery.

Purple fringing can occur in high contrast areas with any lens. You can reduce purple fringing by stopping down your lens. No need for such high shutter speeds on those images.
02-17-2011, 10:23 AM   #4
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QuoteOriginally posted by travy45 Quote
Hi!

Quite often I have purple fringes in my photos, meanwhiles I was told that this is no problem of the K5 but a problem of the DA 18-135. I add two photos, one where you can see windows with purple, even green fringes. The second one has purple fringes at the corner of an hut and in the branches of an tree - but I must not explain, it is quite obvious.

I am taking my photos in RAW (unfortunately except the photo of the hut), until now I used DxO to develop the RAW-files .Since quite often the photos get worse with this software I take now the Pentax Utility, maybe I will buy Lightroom later.

Is there anybody who has similar problems with the DA 18-135?

Best wishes, thanks for your help ... Josef
Welcome to the forums.

I don't know who told you that (the highlighted part) but they were less than truthful or knowledgeable about it. I won't outright say they lied but came close to it.

Some lenses are better at handling it than others but to a degree, they will all do it given the conditions you show. The easiest way to deal with it is use a software that can pick an individual color and desaturate it. The Gimp is a freebie that will do so. If you want to pay money for something to handle it, Photoshop Elements will do it as well I believe.

Re the K5 specifically.. The recent crop of cameras have lens correction functions in their JPG producing software that is supposed to take care of aberrations for some Pentax lenses (it will not work with non Pentax lenses) but it only does so for the JPG output of the camera. The software supplied with the camera is Supposed to mimic the functions of the camera in this respect. The 18-135 was introduced near or slightly later than the K5 IIRC and it is entirely possible that the functions are not there for that lens yet (I don't know that for a fact though).




Last edited by JeffJS; 02-17-2011 at 10:29 AM.
02-17-2011, 01:15 PM   #5
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QuoteOriginally posted by JeffJS Quote
Welcome to the forums.

I don't know who told you that (the highlighted part) but they were less than truthful or knowledgeable about it. I won't outright say they lied but came close to it.

Some lenses are better at handling it than others but to a degree, they will all do it given the conditions you show. The easiest way to deal with it is use a software that can pick an individual color and desaturate it. The Gimp is a freebie that will do so. If you want to pay money for something to handle it, Photoshop Elements will do it as well I believe.

Re the K5 specifically.. The recent crop of cameras have lens correction functions in their JPG producing software that is supposed to take care of aberrations for some Pentax lenses (it will not work with non Pentax lenses) but it only does so for the JPG output of the camera. The software supplied with the camera is Supposed to mimic the functions of the camera in this respect. The 18-135 was introduced near or slightly later than the K5 IIRC and it is entirely possible that the functions are not there for that lens yet (I don't know that for a fact though).

Hi JeffJS!

Maybe there was a problem of translation: the man to whom I showed the same photo in a Germanan DSLR-Forum told me - to my relief - that these purple fringes are not caused by the K5 Camera. That means I can buy e.g. the DA15mm lt. and will not have this problem with purple or green fringes as I have with the DA 18-135 - that would be good news!

I use Gimp very often,I think it is excellent for minor corrections but I doubt that it could remove these fringes in both photos. Because of the high price of Photoshop I hesitate until now to buy this program, do you think Photoshop Elements could remove the purple fringes as well?

Thanks for your help .... Josef
02-17-2011, 01:42 PM   #6
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QuoteOriginally posted by travy45 Quote
Hi JeffJS!

Maybe there was a problem of translation: the man to whom I showed the same photo in a Germanan DSLR-Forum told me - to my relief - that these purple fringes are not caused by the K5 Camera. That means I can buy e.g. the DA15mm lt. and will not have this problem with purple or green fringes as I have with the DA 18-135 - that would be good news!

I use Gimp very often,I think it is excellent for minor corrections but I doubt that it could remove these fringes in both photos. Because of the high price of Photoshop I hesitate until now to buy this program, do you think Photoshop Elements could remove the purple fringes as well?

Thanks for your help .... Josef
I misread your statement so apologies to anyone offended. Fact is though, pick any lens on my list and I can make it display some degree of fringing, even the most expensive one, the FA*85. There are ways of controlling it or minimizing it but it's always possible (you'll have to wait until I get my K5 back from service though).

You can get a free 30 day trial of any adobe product (you can in the USA anyway) and give it a try. I use full blown photoshop and the procedure is quite simple. A simple matter of choosing the color and turning down the saturation for that specific shade. I tried it with Gimp and stand corrected there. For this method to work you have to actually be able to select the color in the photo. That may be possible but I don't know how to do it.

02-18-2011, 06:04 AM   #7
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One thing might need to be added. I believe the K5 will allow for CA correction in the camera, if you activate this option. Might work looking into.
02-18-2011, 07:50 AM   #8
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QuoteOriginally posted by bdery Quote
One thing might need to be added. I believe the K5 will allow for CA correction in the camera, if you activate this option. Might work looking into.
Yes, the camera can. However, it will be taking a few seconds per photo after it is taken and also slow do the contineous shooting speed.
Another Adobe product, which I believe is better for this kind of purpose, is Lightroom.
http://www.adobe.com/cfusion/tdrc/index.cfm?product=photoshop_lightroom&promoid&promoid=DTEML

Lightroom & Photoshop come with standard lens correction profiles, unfortunatly the 18-135mm is not in there yet.

Cheers, Bert

02-18-2011, 09:11 AM   #9
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Hello!

I found by chance that "Pentax Digital Camera Utility 4" offers a CA-correction which is quite effective. I tried to improve a photo with the automatic correction and was surprised, that the purple and green fringes had nearby completly gone. That was with a RAW, I don't know if this program works as good with JPGs.

Best wishes ..... Josef
02-18-2011, 07:02 PM   #10
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I use PSP X3 which is also very good at removing CA and it does not matter whether it is JPEG or RAW it does a good job

Note if you look for it you will find a little CA in any lens some obviously worse than others

If uou use in camera correction it is applied to pentax lenses only (obviously) and slows down image processing and burst rate
02-19-2011, 11:54 AM   #11
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I think I have to purchase either PSP X3, Lightroom or a similar program not only for lens correction but to improve and organize my photos. My niece who is photographer recommends Lightroom.

Thanks to Toronto ... Josef
03-31-2011, 09:53 AM   #12
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Purple Fringing Vs. Chromatic Aberration

I think there is some confusion as to purple fringing vs CA. CA is typically easily removed if it is fairly uniform... however, purple fringing is not so easily corrected. I have a 70-300mm tamron that has nice sharpness, but I absolutely hate the purple fringing it produces as it is hard and time consuming to correct it.
From what I can tell in the picture there is the magenta and cyan aberrations, which look similar to what the kit lense produces. typically not a huge deal. I dont see much evidence of purple fringing but not viewing it at a magnified ratio, it can be hard to tell.
I was considering this lens, but if there is an issue with P.F.... forget it.
03-31-2011, 10:08 AM   #13
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Also remember that superzooms exhibit more aberrations than other lenses, especially wide-open or close to wide-open!

Adam
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