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02-17-2014, 02:09 PM   #1
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35mm Macro green fringing

I recently purchased a Pentax 35mm DA Limited Macro lens, and have been getting a lot of green fringing, particularly in areas like rocks and stucco. Does anyone know if this is normal, or if maybe
there is a defect in my lens?

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02-17-2014, 02:17 PM   #2
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Is it axial CA? (also known as bokeh CA)
This mostly occurs when you are shooting near wide open, and it causes bokeh in front and behind the area in-focus to be coloured purple and green/yellow
This kind of CA isn't as easy to remove, but I think the latest version of Lightroom has a function for it
02-17-2014, 02:35 PM   #3
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Hi! Welcome to the Pentax Forums! What you are describing sounds like chromatic aberration. Green is generally lateral CA and is not related to plane of focus and is relatively easy to remove in PP using tools such as Lightroom. Klaus at photozone.de found what he considered to be unacceptable lateral CA with the DA 35/2.8 Limited at narrower apertures so it is not completely unexpected.


The strange thing is that I don't see any CA on the photo you posted above.

http://www.photozone.de/pentax/393-pentax_35_28


Steve

Last edited by stevebrot; 02-17-2014 at 02:43 PM.
02-17-2014, 02:36 PM   #4
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Umm... Where do you see fringing here? Anyway, Na Horuk is correct, although longitudinal ("normal") CA can also be green.

02-17-2014, 02:56 PM   #5
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If you shoot jpeg you can enable the lens correction (CA correction?) and that ought to help out. But keep in mind that lens correction can take a little longer to process, so the camera might appear slower. Distortion correction is even worse, I think.
If you shoot raw, the regular CA is also relatively easy to fix. Some software have a switch for it, others have manual sliders, and some have a lens profile that you select.

The only other thing that could be problematic is fringing, but that is usually purple. This happens at high contrast areas (like dark tree branches and bright sky).
To help with overall image quality, I suggest you use the lens hood. Also, if you have a filter mounted it can introduce odd things like ghosting or flare. You probably won't ever need an UV filter.
02-17-2014, 03:00 PM   #6
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QuoteOriginally posted by Giklab Quote
Umm... Where do you see fringing here? Anyway, Na Horuk is correct, although longitudinal ("normal") CA can also be green.
Longitudinal (a.k.a axial, LoCA): plane of focus varies by color

Lateral (a.k.a transverse, LaCA): various colors are displaced laterally at the plane of focus

LoCA shows as a single color on all sides of an object (full fringe). A common example would be yellowish on the near side and bluish on the far. The near side color is usually not visible. Lateral CA shows as one color on one side of an object and (not always visible) the complementary color on the other side. An example would be greenish on the left side and magenta on the right. In both type of CA, there is a degradation of image sharpness. This is the most important factor and is true for monochrome as well as color photography.

In my experience with the lenses I own, greenish CA is generally of the lateral type and is usually easily corrected with a general improvement in image sharpness across the frame.


Steve

Last edited by stevebrot; 02-17-2014 at 03:07 PM.
02-17-2014, 04:05 PM   #7
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I know that the green fringing is hard to see on this picture, but it is usually only visible at least a 2:1 zoom. The green areas seem to show up more often when I shoot wide open at f2.8 and when my pictures are underexposed. They are usually in the shadow areas, like in the shadows in this stucco or in between crevices in rocks. I always shoot in raw and edit in Lightroom 5. Using the checkbox for remove ca, I can remove most of it. If I use the color sliders I can remove more of it, but sometimes at the expense of legitimate color in other areas. What should I be doing to minimize this type of CA, or is it just a normal occurrence? With my other two lenses, (kit zoom lenses), I get a lot of purple fringing, but this green fringing is kind of new. When I read the review of this lens on this website, it said that the CA was minimal, so I also wanted to make sure that it wasn't an issue with my lens.
02-17-2014, 04:13 PM   #8
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QuoteOriginally posted by twostewcrew Quote
What should I be doing to minimize this type of CA, or is it just a normal occurrence?
Well you are looking at 2:1 at the weakest spots lol
I suggest you use the lens profile that Lightroom has for that lens.
Axial fringing (longitudinal, bokeh) is unfortunately quite common in most Pentax lenses, wide open. Only things you can do is stop down the lens or choose subjects where this is not a problem or shoot over/underexposed, which ever works best for that lens. The other thing is fixing it in post. But keep in mind, even look at the photo 1:1 is being overly critical. At 2:1 you are literally magnifying the flaws. Only photographers look at photos in such a hyper-critical way, if you show it to people at regular viewing distance they will never notice this.

02-17-2014, 04:25 PM   #9
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Pretty normal for the DA35 Macro. For a real bokeh fringefest try the DA70
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02-17-2014, 06:14 PM   #10
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QuoteOriginally posted by twostewcrew Quote
usually only visible at least a 2:1 zoom.
You mean 2x magnification of a full resolution crop? At that level you are not even looking at a camera-generated image any more. Each pixel of CA has at least one artifact pixel added to the mix by software extrapolation. I would suggest using the CA adjustment in Lightroom at 1:1 as your best effort and forget about subtracting color. If you still feel that the CA is too high for your requirements, you may want to consider a different lens, one with APO in the name. The APO stands for apochromatic and indicates design and manufacturing aimed at undetectable chromatic aberrations.

http://en.wikipedia.org/wiki/Apochromat

As you noted and the comments have also mentioned, there is no visible CA in the image you posted. That really should be good enough.


Steve

---------- Post added 02-17-14 at 05:21 PM ----------

QuoteOriginally posted by Na Horuk Quote
But keep in mind, even look at the photo 1:1 is being overly critical. At 2:1 you are literally magnifying the flaws. Only photographers look at photos in such a hyper-critical way
Ya think? The only times I EVER evaluate at 1:1 is:
  • When correcting CA visible at lower magnifications
  • When adjusting sharpening


Steve
02-28-2014, 05:36 PM   #11
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QuoteOriginally posted by stevebrot Quote
The APO stands for apochromatic and indicates design and manufacturing aimed at undetectable chromatic aberrations.
The sigma definition is for APO: near enough is good enough.

There aren't any Apochromatic lenses currently available for DSLR cameras that are any wider than 100mm
02-28-2014, 06:28 PM   #12
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QuoteOriginally posted by Digitalis Quote
The sigma definition is for APO: near enough is good enough.
Almost Pretty OK?
02-28-2014, 06:39 PM   #13
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I think this is an example of the not-so-great bokeh on DA 35 limited. If you shoot this as a general walk about prime rather than macro, you might enjoy the DA40 quite a bit more.
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