Question for 85/1.2 owners re CA
/forum/topic/808069/0

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slobodan
Registered: Sep 25, 2004
Total Posts: 539
Country: United States

I shot this with my 85/1.8 @ f/2, natural light:



This image is copyrighted by the owner




What bothers me is a quite visible green and purple chromatic aberration (me think):

Upper left corner at 100% (note the "green" hair):



This image is copyrighted by the owner




And lower right corner:



This image is copyrighted by the owner




The question for 85/1.2 owners: is such CA equally visible with your "L" lens?


PetKal
Registered: Sep 06, 2007
Total Posts: 18525
Country: Canada

Yes, and more......all the way up to f/2.2 my 85L MkI is quite susceptible to purple/green fringing.
BTW, very nice portrait of a very pretty girl.



MTBtrials
Registered: Feb 04, 2008
Total Posts: 1368
Country: United States

Wow... I wouldn't notice anything like that.

I rented the 85L to shoot a wedding and quickly realized that you have to shoot without any comp (especially if you open it up a little bit) or else you get bad CA when shooting anything too contrasty.

(on a 40D mainly wide open at 1.2)



Greg Feldman
Registered: Mar 14, 2005
Total Posts: 5841
Country: United States

Yes. Superfast lenses are like that.



slobodan
Registered: Sep 25, 2004
Total Posts: 539
Country: United States

PetKal wrote:
Yes, and more......all the way up to f/2.2 my 85L MkI is quite susceptible to purple/green fringing.
BTW, very nice portrait of a very pretty girl.


Thanks... she is ten years old. What bothers me even more is that none of the CA sliders in Lightroom has any effect whatsoever on that fringing... with all other lenses, it is usually a breeze to get rid of CA in Lightroom.



Dawei Ye
Registered: Sep 15, 2007
Total Posts: 3470
Country: Australia

Yeah those sliders don't work, they are more effective at cleaning up lateral CA than longitudinal CA



Lance Couture
Registered: Aug 08, 2007
Total Posts: 2121
Country: Canada

slobodan wrote:
PetKal wrote:
Yes, and more......all the way up to f/2.2 my 85L MkI is quite susceptible to purple/green fringing.
BTW, very nice portrait of a very pretty girl.


Thanks... she is ten years old. What bothers me even more is that none of the CA sliders in Lightroom has any effect whatsoever on that fringing... with all other lenses, it is usually a breeze to get rid of CA in Lightroom.


If you head over to the Post Processing Forum, there are lots of really great techniques people can show you to clean up CA's like that in PS.



Daan B
Registered: Aug 16, 2007
Total Posts: 7157
Country: Netherlands

Try it @ f/1.2... if you think this is a bad case of CA



Daan B
Registered: Aug 16, 2007
Total Posts: 7157
Country: Netherlands

Dawei Ye wrote:
Yeah those sliders don't work, they are more effective at cleaning up lateral CA than longitudinal CA


The only LR tool that has some effect on the fringes is the "defringe" checkbox.



skibum5
Registered: Jan 21, 2005
Total Posts: 10231
Country: United States

slobodan wrote:
PetKal wrote:
Yes, and more......all the way up to f/2.2 my 85L MkI is quite susceptible to purple/green fringing.
BTW, very nice portrait of a very pretty girl.


Thanks... she is ten years old. What bothers me even more is that none of the CA sliders in Lightroom has any effect whatsoever on that fringing... with all other lenses, it is usually a breeze to get rid of CA in Lightroom.


yeah front/back CA is harder to correct

most fast canon lenses are not full APO designs so they only shift up blue to red and leave green behind so you get magenta in front of focus and green behind it

the canon super-tele are fully correct, as appear to be the macro lenses

it varies in degree lens to lens the 50 1.4, 85 1.8, 85 1.2, 135 2 certainly have it noticeably



Uncle Mike
Registered: Aug 10, 2009
Total Posts: 191
Country: United States

slobodan wrote:
What bothers me even more is that none of the CA sliders in Lightroom has any effect whatsoever on that fringing... with all other lenses, it is usually a breeze to get rid of CA in Lightroom.


Those sliders only fix lateral CA.

You're seeing what I think is correctly called spherochromatism. Longitudinal CA is corrected in the focal plane, but outside the focal plane it's not. It seems to be a result of a complicated lens trying to correct a lot of stuff while ignoring this issue. I don't believe that the cheapie Canon EF 50mm f/1.8 has this issue.

For the price of an "L" lens, one is entitled to expect more perfection, in my worthless opinion.



slobodan
Registered: Sep 25, 2004
Total Posts: 539
Country: United States

MTBtrials wrote:
... I rented the 85L to shoot a wedding and quickly realized that you have to shoot without any comp...


I am not sure I understand what you meant by "shoot without any comp"?



slobodan
Registered: Sep 25, 2004
Total Posts: 539
Country: United States

Daan B wrote:
Try it @ f/1.2... if you think this is a bad case of CA


Just to make sure there is no misunderstanding, the original shot was done with a 40D and 85/1.8 lens (i.e., not the "L" one). The reason I titled this thread as a question for 85/1.2 owners is to basically ask if shelling out $1500 more for the "L" lens would eliminate or reduce the problem with CA... based on the replies so far, it seems it would not, unfortunately. Furthermore, given that the above shot is done with a crop sensor, it seems logical that on a full frame the CA would be even more pronounced.



slobodan
Registered: Sep 25, 2004
Total Posts: 539
Country: United States

Daan B wrote:
... The only LR tool that has some effect on the fringes is the "defringe" checkbox.


Tried that as well, no visible effect.



Uncle Mike
Registered: Aug 10, 2009
Total Posts: 191
Country: United States

slobodan wrote:
Furthermore, given that the above shot is done with a crop sensor, it seems logical that on a full frame the CA would be even more pronounced.


No, just the opposite seems logical. A green fringe with a width of 20 microns would cover a greater percentage of the picture area on an APS-C camera than on a FF camera.



Ernie Aubert
Registered: Apr 19, 2007
Total Posts: 2873
Country: United States

I once saw on a web site a set of images of a mannequin head shot with the 85 1.8, the 85 1.2L I, and the 85 1.2L II, and the CA diminished progressively with price. I would expect that you'd have had less of it with the 1.2 II at the same aperture. (That would qualify as my worthless opinion.)



phuang3
Registered: Feb 09, 2005
Total Posts: 832
Country: Taiwan

My suggestion is to use a long tele for this kind of portrait. Try a EF135/2 or EF200/2 which has much better LCA correction.



rscheffler
Registered: Aug 23, 2005
Total Posts: 2840
Country: Canada

Ernie Aubert wrote:
I once saw on a web site a set of images of a mannequin head shot with the 85 1.8, the 85 1.2L I, and the 85 1.2L II, and the CA diminished progressively with price. I would expect that you'd have had less of it with the 1.2 II at the same aperture. (That would qualify as my worthless opinion.)


Are you thinking of this? http://www.wlcastleman.com/equip/reviews/85mm/index.htm

BTW, he writes in the above review comparing the 85 1.8, 85L and 85L II: Birefringence patterns produced from f/1.4 to f/4 with the 3 lenses on an EOS-1Ds Mark II are shown here. No differences among the lenses were detected in birefringence induced in metallic/reflective objects at wide apertures with the three lenses using the 1Ds Mark II or an EOS 20D (20D images not shown)



Ernie Aubert
Registered: Apr 19, 2007
Total Posts: 2873
Country: United States

That was it.



sboerup
Registered: Oct 13, 2005
Total Posts: 8869
Country: United States

Not to be insulting, I'm just surprised people worry about this much CA in their pics. I mean, its hardly noticeable at 100%, something you wont see in a print. // end rant



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