FlyPenFly wrote:
So far I've never used any lens that is free of any CA when set to faster than F2.8
Perhaps the Leica APO-Telyt 180/2. At shorter focal lengths you won't find any apochromatic lenses, not at f/2 or faster I think. The Kern Macro Switar 50/1.9 comes to mind though. I believe that one is said to be apo. Not sure if it is really "free from CA" wide open though.
edwardkaraa wrote:
LoCA seem to be a Zeiss trade mark
indeed, i've always wondered if the same design decisions that give their wonderful contrast and color pop also necessarily give them loCA. i've never used a fast lens that was totally free of it but it's never bothered me much on the canon FL 55/1.2.
sebboh wrote:
indeed, i've always wondered if the same design decisions that give their wonderful contrast and color pop also necessarily give them loCA. i've never used a fast lens that was totally free of it but it's never bothered me much on the canon FL 55/1.2.
That is also my theory. I suspect loca is a side effect of the Zeiss look.
Edward, while some Zeiis lenses have loCA, it seems to me that not all of them, especially the Distagon 21. OTOH, I have seen quite a bit of it as well on fast Canon lenses, such as 35L, and 16-35L. My guess is that this is a matter of fast lens design more than of Zeiss itself.
AhamB wrote:
Perhaps the Leica APO-Telyt 180/2. At shorter focal lengths you won't find any apochromatic lenses, not at f/2 or faster I think. The Kern Macro Switar 50/1.9 comes to mind though. I believe that one is said to be apo. Not sure if it is really "free from CA" wide open though.
How about the APO-SUMMICRON-R 90 mm f/2 ASPH? I vaguely recall having read that it is also corrected for LoCA, but when I search I can't find any data or comments. It could be that I put to much into LC's review on his blog, or that I confuse it with the 90 APO macro. Sorry to hijack the Zeiss discussion, but does anyone have any experience, maybe compared to the Z* 100 MP?
philber wrote:
Edward, while some Zeiis lenses have loCA, it seems to me that not all of them, especially the Distagon 21. OTOH, I have seen quite a bit of it as well on fast Canon lenses, such as 35L, and 16-35L. My guess is that this is a matter of fast lens design more than of Zeiss itself.
Of course, what you're saying is true. But I have the impression the under-correction of LoCA in Zeiss lenses is intentional.
I have always thought that the complex field curvature of Zeiss wides plays a certain role in the 3D rendering.
A few years back, in a very long thread about 3D, it seems that LoCA contributes to the 3D rendering as well in lenses like the Contax 35/1.4 and 85/1.4 as it draws a certain contour around the subject. Some very nice examples were shown by brainiac.
This is at F1.4, my friend volunteered for a few tests. It seems at F1.4 its very sharp and useable but it front focused this time about 50% of the shots. It's a slight front focus though so unless looking at it at 1:1 it still looks pretty sharp. I'm a little dissapointed but I think just about every platform and sharp fast AF system will display some slight inconsistency in focus for such distance in a phase detect system.
edwardkaraa wrote:
A few years back, in a very long thread about 3D, it seems that LoCA contributes to the 3D rendering as well in lenses like the Contax 35/1.4 and 85/1.4 as it draws a certain contour around the subject. Some very nice examples were shown by brainiac.
I don't remember that the conclusion was that the contours were caused by LoCA. It's an edge effect that appears at focus transitions, but I've never seen it having the typical LoCA colours. I have a close-up shot with the Distagon 28/2.8 where the effect is strong, but the contour isn't coloured.
AhamB wrote:
I see waveform distortion in Ulff's shot.
I don't remember that the conclusion was that the contours were caused by LoCA. It's an edge effect that appears at focus transitions, but I've never seen it having the typical LoCA colours. I have a close-up shot with the Distagon 28/2.8 where the effect is strong, but the contour isn't coloured.
You are right, it wasn't the conclusion but what else can it be? To my eyes, this edge effect looks exactly like loca, but it is more grayish than blue, especially if you don't crank up saturation. On my ZA 85, the effect is rather bluish gray. I myself am very convinced, but I understand there is no consensus on this issue.
edwardkaraa wrote:
You are right, it wasn't the conclusion but what else can it be? To my eyes, this edge effect looks exactly like loca, but it is more grayish than blue, especially if you don't crank up saturation. On my ZA 85, the effect is rather bluish gray. I myself am very convinced, but I understand there is no consensus on this issue.
This sounds like a case that calls for more informative crops --- please post 'em if you've got 'em. If the edge effects are often color neutral (grayish), then it doesn't sound like LoCA, although it may be an effect for which LoCA is a difficult-to-avoid optical design tradeoff given available glass types. I have seen some crops showing moderately severe LoCA from the Z* Makro-Planar 100/2; it would be interesting if someone could compare this lens head-to-head with the older CY 100/2 Planar (also excellent at "Zeiss 3D") to see how LoCA and edge transitions come into play in both. I only have the CY Planar, which I don't recall having as much LoCA as the Z* Makro-Planar, but it's hard to tell without sufficiently similar comparison pics (ideally from both lenses on an identical target).
I think to find out for sure, we need to do some tests along side similar in class Nikon and canon lenses to make sure this outlining is a Zeiss trait.
