Red CA, a problem?

GalacticPhoto · 08-29-2016, 05:01 PM

Studying the Studio Comparison Image on Dpreview I am noticing a lot of red CA.

Studio shot comparison: Digital Photography Review

**caliscouser** · 08-29-2016, 05:14 PM

It would be a function of the lens used and the particular copy of that lens.

The K70/K3II are on the 55 1.4 and the KS2/K50 are on the 50 2.8.

GalacticPhoto · 08-29-2016, 05:19 PM

Originally posted by caliscouser

It would be a function of the lens used and the particular copy of that lens.

The K70/K3II are on the 55 1.4 and the KS2/K50 are on the 50 2.8.

Yeah, but the K70 is far worse than the K3ii.

**caliscouser** · 08-29-2016, 05:36 PM

Different copy of the same lens??
The K3II image is softer on the left side than the K70.

GalacticPhoto · 08-29-2016, 05:53 PM

Originally posted by caliscouser

Different copy of the same lens??
The K3II image is softer on the left side than the K70.

That might be the case. Though I don't know why they wouldn't just stock the same glass for comparison sake. I also wasn't aware there was that much difference in CA between copies.

DeadJohn · 08-29-2016, 09:03 PM

I'm not seeing a "lot" of CA anywhere. There are hints of it at 1:1 pixel peeping but that's not a problem IMO.

GalacticPhoto · 08-30-2016, 06:08 AM

Originally posted by DeadJohn

I'm not seeing a "lot" of CA anywhere. There are hints of it at 1:1 pixel peeping but that's not a problem IMO.

Did you click the link I provided? It's very obvious.

DeadJohn · 08-30-2016, 06:44 AM

Originally posted by GalacticPhoto

Did you click the link I provided? It's very obvious.

I used the link. It zoomed to a closeup of a brush. The K70 image wasn't objectionable to me, and at 1:1 was arguably better than the K1.

Dan · 08-30-2016, 07:04 AM

Originally posted by GalacticPhoto

Did you click the link I provided? It's very obvious.

I agree that it's very obvious. But it only affects the brushes in the upper left corner of the image. If you examine the same style brushes in the lower right part of the image the nasty fringing is gone, even though the lighting and reflections are very similar. This suggests that it is not a sensor problem, but rather a problem with lens. The lens elements are not perfectly centered. This can affect not just sharpness, but fringing as well.

Why does this not show up with the K3-II? Two possibilities come to mind. First, as others have mentioned, it could be that they used different copies of the lens. Another possibility is that the same lens was focused slightly differently in the two tests. Even very small differences in focusing can affect fringing.

As someone who has done a lot of my own lens testing, I can tell you that it is an extremely difficult thing to do. Small changes in the setup can have noticeable effects on the results. Moreover, modern sensors have such high resolution that they can reveal small flaws in lens assembly and small differences in focus.

Dan

GalacticPhoto · 08-30-2016, 07:49 AM

Originally posted by Dan

I agree that it's very obvious. But it only affects the brushes in the upper left corner of the image. If you examine the same style brushes in the lower right part of the image the nasty fringing is gone, even though the lighting and reflections are very similar. This suggests that it is not a sensor problem, but rather a problem with lens. The lens elements are not perfectly centered. This can affect not just sharpness, but fringing as well.

Why does this not show up with the K3-II? Two possibilities come to mind. First, as others have mentioned, it could be that they used different copies of the lens. Another possibility is that the same lens was focused slightly differently in the two tests. Even very small differences in focusing can affect fringing.

As someone who has done a lot of my own lens testing, I can tell you that it is an extremely difficult thing to do. Small changes in the setup can have noticeable effects on the results. Moreover, modern sensors have such high resolution that they can reveal small flaws in lens assembly and small differences in focus.

Dan

I can see it bottom right, just a hair more than the K3 II though. It's noticeable also bottom left over the K3 II, but only slightly, top right seems about completely gone.

This is why I don't like the Dpreview tests, I don't think they are using the same glass and replicating their tests well enough. I honestly also really hate the scene they are using.

08-29-2016, 05:01 PM	#1
GalacticPhoto Senior Member Join Date: Jan 2016 Photos: Gallery Posts: 106	Red CA, a problem? Studying the Studio Comparison Image on Dpreview I am noticing a lot of red CA. Studio shot comparison: Digital Photography Review

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08-29-2016, 05:14 PM	#2
caliscouser Site Supporter Join Date: Sep 2014 Location: SF Bay Area, CA Photos: Albums Posts: 1,037	It would be a function of the lens used and the particular copy of that lens. The K70/K3II are on the 55 1.4 and the KS2/K50 are on the 50 2.8.

08-29-2016, 05:19 PM	#3
GalacticPhoto Senior Member Join Date: Jan 2016 Photos: Gallery Posts: 106 Original Poster	Originally posted by caliscouser It would be a function of the lens used and the particular copy of that lens. The K70/K3II are on the 55 1.4 and the KS2/K50 are on the 50 2.8. Yeah, but the K70 is far worse than the K3ii.

08-29-2016, 05:36 PM	#4
caliscouser Site Supporter Join Date: Sep 2014 Location: SF Bay Area, CA Photos: Albums Posts: 1,037	Different copy of the same lens?? The K3II image is softer on the left side than the K70.

08-29-2016, 05:53 PM	#5
GalacticPhoto Senior Member Join Date: Jan 2016 Photos: Gallery Posts: 106 Original Poster	Originally posted by caliscouser Different copy of the same lens?? The K3II image is softer on the left side than the K70. That might be the case. Though I don't know why they wouldn't just stock the same glass for comparison sake. I also wasn't aware there was that much difference in CA between copies.

08-29-2016, 09:03 PM	#6
DeadJohn Pentaxian Join Date: Jan 2011 Location: New York Posts: 4,833	I'm not seeing a "lot" of CA anywhere. There are hints of it at 1:1 pixel peeping but that's not a problem IMO.

08-30-2016, 06:08 AM	#7
GalacticPhoto Senior Member Join Date: Jan 2016 Photos: Gallery Posts: 106 Original Poster	Originally posted by DeadJohn I'm not seeing a "lot" of CA anywhere. There are hints of it at 1:1 pixel peeping but that's not a problem IMO. Did you click the link I provided? It's very obvious.

08-30-2016, 06:44 AM	#8
DeadJohn Pentaxian Join Date: Jan 2011 Location: New York Posts: 4,833	Originally posted by GalacticPhoto Did you click the link I provided? It's very obvious. I used the link. It zoomed to a closeup of a brush. The K70 image wasn't objectionable to me, and at 1:1 was arguably better than the K1.

08-30-2016, 07:04 AM	#9
Dan Pentaxian Join Date: Dec 2007 Location: Pacific Northwest Posts: 325	Originally posted by GalacticPhoto Did you click the link I provided? It's very obvious. I agree that it's very obvious. But it only affects the brushes in the upper left corner of the image. If you examine the same style brushes in the lower right part of the image the nasty fringing is gone, even though the lighting and reflections are very similar. This suggests that it is not a sensor problem, but rather a problem with lens. The lens elements are not perfectly centered. This can affect not just sharpness, but fringing as well. Why does this not show up with the K3-II? Two possibilities come to mind. First, as others have mentioned, it could be that they used different copies of the lens. Another possibility is that the same lens was focused slightly differently in the two tests. Even very small differences in focusing can affect fringing. As someone who has done a lot of my own lens testing, I can tell you that it is an extremely difficult thing to do. Small changes in the setup can have noticeable effects on the results. Moreover, modern sensors have such high resolution that they can reveal small flaws in lens assembly and small differences in focus. Dan

08-30-2016, 07:49 AM	#10
GalacticPhoto Senior Member Join Date: Jan 2016 Photos: Gallery Posts: 106 Original Poster	Originally posted by Dan I agree that it's very obvious. But it only affects the brushes in the upper left corner of the image. If you examine the same style brushes in the lower right part of the image the nasty fringing is gone, even though the lighting and reflections are very similar. This suggests that it is not a sensor problem, but rather a problem with lens. The lens elements are not perfectly centered. This can affect not just sharpness, but fringing as well. Why does this not show up with the K3-II? Two possibilities come to mind. First, as others have mentioned, it could be that they used different copies of the lens. Another possibility is that the same lens was focused slightly differently in the two tests. Even very small differences in focusing can affect fringing. As someone who has done a lot of my own lens testing, I can tell you that it is an extremely difficult thing to do. Small changes in the setup can have noticeable effects on the results. Moreover, modern sensors have such high resolution that they can reveal small flaws in lens assembly and small differences in focus. Dan I can see it bottom right, just a hair more than the K3 II though. It's noticeable also bottom left over the K3 II, but only slightly, top right seems about completely gone. This is why I don't like the Dpreview tests, I don't think they are using the same glass and replicating their tests well enough. I honestly also really hate the scene they are using.