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01-09-2015, 06:07 AM   #1
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Any problems with Chromatic Aberration?

I am very interested in buying a K-3 but one thing that scares me a little is some reviewers pointing out a fair amount of Chromatic Aberration. Anybody fine issues with this and is it as pronounced as some reviewers are saying. A big thank you to anyone who can help me with this.

01-09-2015, 07:11 AM   #2
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It seems to be lens dependent more than anything. Which lenses do you plan to use? Have you seen the review section - you can find member written lens and camera reviews there.
01-09-2015, 07:44 AM   #3
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QuoteOriginally posted by spbouvier Quote
Anybody fine issues with this and is it as pronounced as some reviewers are saying.
"By definition" a camera(sensor) cannot show CA, because that is a lens property, (the lens does not focus light of different wavelengths in the same plane). Do you have any links to those reviewers?
01-09-2015, 07:50 AM   #4
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CA is a function of the lens.
QuoteQuote:
In optics, chromatic aberration (CA, also called achromatism, chromatic distortion, and spherochromatism) is a type of distortion in which there is a failure of a lens to focus all colors to the same convergence point.
It is just being recorded by the body (sensor) [K3] with more resolution. For the most part, it can be corrected in post processing.



01-09-2015, 08:14 AM   #5
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Yep, like people said above. CA is a lens property, some lenses show more CA, others less. Typically, more high end, expensive lenses will have less CA. But it also depends on the lens design, coatings, etc. CA is also not noticeable in all photos equally - if the photo is a landscape full of trees with leaves and no sky, you will see almost no CA. If you take a photo of three cones against a background, you will be more likely to notice CA. Modern lenses are pretty good with CA, though. Pentax is really good with lowering lateral CA, but is known to have a little axial/bokeh CA wide open (again, not all lenses. Some say the reason for this is that axial CA correction can make the bokeh look worse and Pentax likes nice bokeh, even at the cost of lab measured CA scores)

There are a number of things you can do against CA btw. Pentax DSLRs contain lens profiles for all modern Pentax lenses (the ones with lens ID), so if you shoot jpeg, the camera can automatically correct CA, as well as other lens properties like distortion, vignetting. This takes a little processing power, though. If you shoot raw, the raw software (Lightroom, FastStone, Aperture,..) usually has some way to manually remove CA. Many software also support lens profiles, so you don't have to do any work.

CA is one of those things that can really drive a photographer mad, but most viewers will not even notice it. On digital cameras, there are a number of ways to minimize CA. If you worry about CA, check lab tests of the lenses you are buying, don't worry about the camera. Fact is, a good camera, with high resolution, will "capture" the CA in more detail than a low end camera with less resolution. Just like it captures more detail overall. The K-3 is no worse at CA than any other camera. Those reviewers did a poor job if they blamed the CA on the camera. I would not trust their opinions

Digital sensors can cause some optical problems, like sensor being shiny and reflecting off the back of the lens, but Pentax has not had any problems with this (and the lens is a big part in this problem, as well. Modern lenses do not have this problem)

tl;dr: K-3 does not have problems with CA. Some specific lenses (from all manufacturers) may have problems with CA. There are many methods of minimizing and removing CA.
01-09-2015, 08:24 AM   #6
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While of course it is a lens property, there are little micro lenses on the sensor pixels, the angle at which light hits the pixels matters (unlike film), and of course the size of those pixels is different from sensor-to-sensor so the light isn't always broken up the same way. And the surface of the sensor could be more or less reflective which the light has to pass through (which even if it doesn't cause any CA, which it might, it can cause weird flare/internal reflections with some lenses). So it seems to me that the sensor system could also contribute some level of CA, or at least render the given CA from the lens differently. Certainly I got the sense when moving to the K-5 that I was seeing more purple fringing than I had been previously with either the K10D or the K-7 with the same lenses, but it could be all in my head.
01-09-2015, 08:38 AM   #7
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Welcome to the Pentax Forums!

As noted above, chromatic aberration is related to lens design. There is another problem, loosely referred to as "purple fringing" (abbreviated PF), that is sensor related, but may be exacerbated by longitudinal CA. I suspect that is the CA you are inquiring about. To answer your question in that context, the K-3 is no more susceptible to PF than other cameras having similar sensors (e.g. Nikon D7100). With most modern lenses, it is not a problem.


Steve

Last edited by stevebrot; 01-09-2015 at 08:48 AM.
01-09-2015, 08:46 AM   #8
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QuoteOriginally posted by Na Horuk Quote
Digital sensors can cause some optical problems, like sensor being shiny and reflecting off the back of the lens, but Pentax has not had any problems with this
At risk of derailing the thread, I have to chuckle a little on this one. The reflective hot spot phenomenon* does affect Pentax cameras including my K-3 and the K10D that preceded it. In fact, I first read of it and saw demonstration of it on this site.


Steve

* Caused by lenses having a large, flat rear element. Under some circumstances reflection off the rear glass will overlay as a hot spot at center of frame.

01-09-2015, 09:03 AM   #9
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QuoteOriginally posted by stevebrot Quote
At risk of derailing the thread, I have to chuckle a little on this one. The reflective hot spot phenomenon* does affect Pentax cameras including my K-3 and the K10D that preceded it. In fact, I first read of it and saw demonstration of it on this site.


Steve

* Caused by lenses having a large, flat rear element. Under some circumstances reflection off the rear glass will overlay as a hot spot at center of frame.
To be fair, I don't think there are any Pentax lenses that have this problem, at least not any modern ones. The only modern lens I've ever gotten a hotspot with is the Sigma 8-16 where I get a purple spot right in the center sometimes, but I think it is because at the extreme you can actually get the front element of the lens itself in-focus. (Looks different than other reflections I've seen, but of course the 8-16 is quite different in design that most anything else.)
01-09-2015, 11:41 AM   #10
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While I am aware of at least two K-3 reviews mentioning fringing issues, I haven't found it significant enough to affect my real-world shooting. In fact, I don't have the feeling that I have to do deal with any more purple fringing in Lightroom than I used to have to with my old K-7, and the correction options in Lightroom 4 and 5 have made PF pretty much a non-issue for me.

Such reports have certainly not deterred me from buying a K-3, and I'm glad they didn't, because I'm still blown away by its gorgeous output.

For those inclined to dig deeper, here are links to the two reviews I have in mind. One is the really conscientious review from trusted imaging-resource.com, the other a rather silly and not-seeing-the-wood-for-the-trees review from Digital Camera World (UK) seen on youTube:

Pentax K-3 Review - Shooter's Report Part II

01-09-2015, 01:04 PM   #11
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QuoteOriginally posted by spbouvier Quote
I am very interested in buying a K-3 but one thing that scares me a little is some reviewers pointing out a fair amount of Chromatic Aberration. Anybody fine issues with this and is it as pronounced as some reviewers are saying. A big thank you to anyone who can help me with this.
I think PF is a function of the lens not the camera body. All my lenses have some degree of purple fringing (PF). I am not sure if it can be totally eliminated. Perhaps minimized as much as possible.

Oddly enough the worst offenders for me are my (expensive) FA Limited lenses (The Three Amigos). They all have terrible purple fringing wide open. The PF goes away by f4 or so. I am not too worried as PF is an easy fix in Photoshop or Lightroom. I am not sure how expensive a lens needs to get for it to be corrected for PF in the glass. The Zeiss 50mm Otus which is not available for Pentax is one such lens. It is priced at $4,000 or so.

My 16-45 Pentax zoom has all sorts of color fringing. For example, with a tree branch shot against a bright sky, one side of the branch's edge is green and the other side has orange edges. Weird. I don't think I have seen this kind of fringing in any other lens. Credit to Photoshop and Lightroom, even this kind of complex lens aberration is correctable!

I have seen terrible PF on a bunch of my older manual lenses. For me it is important that the lens is sharp. You cannot correct a soft lens but PF and other aberrations can be corrected.
01-09-2015, 01:13 PM   #12
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QuoteOriginally posted by btnapa Quote
My 16-45 Pentax zoom has all sorts of color fringing. For example, with a tree branch shot against a bright sky, one side of the branch's edge is green and the other side has orange edges. Weird. I don't think I have seen this kind of fringing in any other lens. Credit to Photoshop and Lightroom, even this kind of complex lens aberration is correctable!

With the 16-45 do you use the in camera distortion corrections or do you shoot without that enabled?
01-09-2015, 01:32 PM   #13
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QuoteOriginally posted by UncleVanya Quote
With the 16-45 do you use the in camera distortion corrections or do you shoot without that enabled?
I have not tried the in-camera correction with my K3. I tried it with my K5IIs and it was taking time to process each image after the click of the shutter. So I decided to do all my corrections in the computer where it is a lot faster. If you shoot JPEGs perhaps the in-camera correction is the way to go. But if you shoot in RAW, my suggestion is to do any correction in post. Aside from the fact that the in-camera correction did not seem to be all that good anyway.
01-09-2015, 02:46 PM   #14
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Follow up question - did your software have lens profiles for the 16-45 to automatically adjust for distortion or were you manually adjusting?
01-09-2015, 02:54 PM   #15
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QuoteOriginally posted by Madaboutpix Quote
One is the really conscientious review from trusted imaging-resource.com, the other a rather silly and not-seeing-the-wood-for-the-trees review from Digital Camera World (UK) seen on youTube:
I had seen the IR review and felt at the time that the faux color was not particularly critical, but that it was good of them to mention it. For those not wanting to click through, below is the IR image. The faux color in question is on the bottom of the glare in the glass lamp of this full resolution crop:



The Digital Camera World review is, as you said, silly.

My experience with the K-3 has been that PF is not pronounced with any modern lens and not particularly severe even with lenses having the reputation of triggering a purple fringe (e.g. FA 77/1.8, FA 35/2).


Steve
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