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S2 Chromatic Aberration - how big an issue is it?

narikin

New member
In 3 days testing of an S2 with the 70mm 'standard' I noticed a fair bit of CA in my images at wider apertures. Slightly more than their competitors (Hassy, Phase) and a LOT more than you would expect from Leica's reputation.

From odd hints here, it seems to be something that others have noticed too, though all the big tests seem to rarely mention it - is this the case, or did I miss a larger discussion?
 

tjv

Active member
I've heard it mentioned before. You've got to wonder, again, if the other big boys don't do a lot of their CA removal automatically in firmware and fine tuned software, eg. Phocus and C1. Lightroom has never been good with CA, at least not in my experience with Nikon and Canon glass. I too find it hard to swallow that the most expensive glass in the MF world exhibits such strong CA at wider apertures. Can you post some examples? I'm hoping to test the S2 in the coming month as well so any shared info would be great.
T
 

ptomsu

Workshop Member
Hm, actually that does not sound good.

Maybe the lens needs some fine tuning? Reminds me back on my DMR time, when I used my 2.8/180 APO first time with the DMR I had quite a lot of CA. Sending the lens back to Solms and have it adjusted again helped. No more visible CA.

Would have hoped this problem was gone with the new designed glass for the S System, but obviously not. My conclusion is that the lens needs to be fine tuned. I do not think that Leica relies on CA removal during post processing, so either they do it in camera for the rest that remains in a high end lens, or the lens is so misaligned that the internal CA removal does not help.
 

markowich

New member
this is a very interesting issue. i have noticed a lot of CA in my first tests with the S2 and the 70mm lens but other issues at that time were overiding. some of the samples taken with the 35mm posted on the net show the same but i thought it was jpg processing. also, some of my M lenses like the 24mm LUX and the 50mm LUX show exaggerated CA, when compared to nikkors for example. of course LR is very bad with CA, much worse than C1. there could be many other reasons like the glass leica uses, internal processing etc.
disturbing anyway.
peter
 

ptomsu

Workshop Member
I still think it is a matter of exact adjustment. As already mentioned, it was repaired after sending my 180 APO to Solms. Also all of my M glass was there for coding and adjustment and I never had any issues with it afterwards.

Disturbing is that obviously Leica QC is not what it should be!
 

robmac

Well-known member
I stand to be corrected on this (obviously) but I'm not convinced (on only 1 cup of coffee) a buff & polish back at the Solms mothership would help much with CA on a non-apo lens - assuming all else is as it should be with the lens. I can see it helping enormously with an APO unit that's seen some knocks...

As for CA w/S2:

http://luminous-landscape.com/forum/index.php?s=&showtopic=44543&view=findpost&p=374041

Got a kick out of the "...wasting money..." part.
 
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The topic of CA and the Leica S2/lenses came up a few days ago in the "fun with MF" thread when Jack noticed CA visible in some S2 photos of motorcycle chrome was posted. This got me curious so I went back through a few thousand of my S2 images and had a very difficult time finding photos that show CA. There were very few images with CA and only in the most extreme conditions. So, it has been a non-issue for me.
 

Jack

Sr. Administrator
Staff member
Actually it came up in Guy's and my review of the S2 back in January, but at that time we expressed caution in reading too much into it as there was no dedicated raw processor yet. Unfortunately it seems there is still no dedicated raw processor, so for now the CA appears in certain circumstances, so seems it could be an issue for folks that use them in those circumstances....
 

John Black

Active member
As TJV pointed out, the big unknown here is the raw editor. The software companies are not fully transparent in explaining how their editors work - understandably so since that's core to their app's design / performance/ differentiators. The problem comes into play when using one app for one camera, and another app for another camera. There list of unknowns is lengthy and all we can do is look at the net result and make judgements & best guesses. I posted this a while back -



At the time C1 was automatically suppressing purple CA, there was no toggle switch to turn it on and off in the non-pro version. So I could go on and on for years believing XYZ lens didn't have CA simply because C1 filtered it out and I was none the wiser. I'm not defending Leica here, just illustrating TJV's comments. And I hope Leica re-evaluates their raw editor strategy.
 

ptomsu

Workshop Member
The topic of CA and the Leica S2/lenses came up a few days ago in the "fun with MF" thread when Jack noticed CA visible in some S2 photos of motorcycle chrome was posted. This got me curious so I went back through a few thousand of my S2 images and had a very difficult time finding photos that show CA. There were very few images with CA and only in the most extreme conditions. So, it has been a non-issue for me.
Maybe you had the luck of optimally aligned and adjusted lenses?
 

ptomsu

Workshop Member
I stand to be corrected on this (obviously) but I'm not convinced (on only 1 cup of coffee) a buff & polish back at the Solms mothership would help much with CA on a non-apo lens - assuming all else is as it should be with the lens. I can see it helping enormously with an APO unit that's seen some knocks...

As for CA w/S2:

http://luminous-landscape.com/forum/index.php?s=&showtopic=44543&view=findpost&p=374041

Got a kick out of the "...wasting money..." part.
I have mainly APO and ASPH lenses I use on the M8 and for most of them sending back to Solms solved the problem. Same as for the 2.8/180 APO.

So you are right, for non APO and maybe also non ASPH lenses ther can be only little improvement WRT CA.
 

robmac

Well-known member
Peter, no definitive idea - just a random thought while contemplating which blend to have for my 2nd morning coffee.
 

fotografz

Well-known member
Are we talking about CA here ... or purple/magenta fringing from digital sensor bloom?

I saw some green CA from the S2 70mm ... like partially OOF palm tree trunk edges against a blue sky background, but not to bad actually ... and some pretty bad Purple/Magenta fringing on hard edged objects agains a bright window ... LR didn't even touch that Purple fringing.

For the most part, both the 70mm and the 180mm I used with the S2 did pretty good given the bright conditions I was shooting in. But frankly not any better than other MFD systems I've used, even without using de-fringing software other than what's available in LR.

-Marc
 

Jack

Sr. Administrator
Staff member
Are we talking about CA here ... or purple/magenta fringing from digital sensor bloom?
Good point Marc -- it is purple fringe I saw with the S2 on all occasions. CA would also have a blue or green opposite component depending on whether the "purple" is red or magenta...
 

NotXorc

New member
Interesting thread. I am also curious how well the LR solution allows taming of CA. Those who advocate use of dedicated system software (and we already KNOW who you are :D ) may have a good point.

As always, pixel peeping only makes sense if everyone who sees your work gets to do it too. Were those who have seen CA in the S2 lenses still able to see it in a 40"x60" print? Okay, now 20"x30"?
 
Marc, you are probably right in that it is purple fringe more so than CA. I have attached an example (with crop) of one of my S2-70mm photos which exhibit this. I consider this an extreme condition and is only visible in a tight crop, but it is there. Still, I am not complaining considering the conditions and no attempt has been made to post process the fringing away. Note the crop is the upper right hand corner of the photo.
 
It is also worth noting the DR is better than appears in the small jpg image. See the crop from the lower left portion of the frame. Note, the crop area is not sharp because it is outside the depth of field from the focus point.
 

Jack

Sr. Administrator
Staff member
It is also worth noting the DR is better than appears in the small jpg image. See the crop from the lower left portion of the frame. Note, the crop area is not sharp because it is outside the depth of field from the focus point.
That's CA -- mild, but CA. You have magenta along the lower edge of the downspout and rail, and then a slight bit of green along the opposite edges.
 

Guy Mancuso

Administrator, Instructor
Interesting thread. I am also curious how well the LR solution allows taming of CA. Those who advocate use of dedicated system software (and we already KNOW who you are :D ) may have a good point.

As always, pixel peeping only makes sense if everyone who sees your work gets to do it too. Were those who have seen CA in the S2 lenses still able to see it in a 40"x60" print? Okay, now 20"x30"?
My ears are ringing but the truth is C1 is excellent at controlling CA and yes I have run into it with the Phase on occasion with a 28mm but hit a button and it is gone . I don't think it functions with a S2 file though because it see's it as a generic DNG.

When Jack and I tested the s2 we where more preoccupied with other things but as Jack said we also where not sure what the software was doing either. So we left it alone but yes we did see it.
 

d_brown

New member
Here's a suggestion for eliminating fringing is Lightroom:

Make any changes or corrections you desire, then apply Defringe to all edges.

Next, export the file as a TIFF to the same folder as the original, and check the "Add to this catalog" box.

Now you have a corrected TIFF file sitting next your original. Just apply Defringe to all edges again, and the purple fringing is gone! The need to do this is only about 1% of your photos where there is extreme contrast present. I have never seen any CA.

Dale
 
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