Fred Miranda wrote:
I don't think purple fringing is related to lateral CA. Purple fringing goes away when stopping down the lens but lateral CA does not. I think it's more related to longitudinal CA and shows up under high contrast around the plane of focus.
Let’s suspend for now the debate about the origin of “purple fringing” - what I am trying to suggest here is to test in such a way as to separate it from the “purple to green” manifestation. The woven chair is quite a bad subject since it offers a lot of edges and, with strong backlight, it will create both manifestations (purple fringing around the edges + purple to green transition). This is quite well exemplified in my (disorienting) photo I think.
I’d suggest to use foliage or small branches against the sky for the “purple fringing” and a smooth surface (such as water or a stainless ruler or a printed page with very white paper) for the “purple to green” thing. Simply because that is how most of us and most review sites test them, so we are familiar with how they (should) look.
I’m pretty sure that the 55mm has a lot of both and that the 50 will cream it, but I’d like to see it as separate effects instead of a sum.
For LoCA using the well-known method of a slanted ruler or similar, it's always seen as magenta (red plus blue) in front, then green behind the focal plane. Here is the test of the FE55 at Optical Limits, in which the lens goes as expected:
'Magenta is a color in between red and purple or pink and purple. Sometimes it is confused with pink or purple. In terms of the HSV (RGB) color wheel, it is the color halfway between red and purple and is composed equally of red and blue (50% red and 50% blue).'
Fred Miranda wrote:
[The 55/1.8 ZA and 50/2 APO have some similarities like strong resolution performance across the field and compactness but also differ in many aspects of IQ. Aside from AF vs MF, color aberration correction is the main difference between these two in my opinion.
Depending on the scene, the 55/1.8 can show very noticeable color fringing (LoCA) and lateral CA as well. On the other hand, the 50/2 APO is very well corrected for CA.
This was taken about an hour apart from each other so lighting changed a bit but it clearly shows this difference in the form of purple fringing which is LoCA on the focus plane. Under high contrast lighting it's really night and day between these two lenses.
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Fred, probably my previous post could/should have been clearer: I don't disagree with your findings, it's obvious to see which lens is better corrected and the comparison between two lenses of similar FL's makes sense. What I was trying to say is that to me AF matters (at least in that particular case) and hence no matter how excellent the 50 APO might be, it couldn't replace the 55 1.8 in my bag. Of course, this doesn't take anything away from the APO's excellent perfromance and I perfectly understand one would pick the CV over the 55 1.8, if AF isn't a major consideration.
I have an AF kit and a MF kit (with a couple crossovers.) Nothing wrong with keeping both and liking both.
Chris_88 wrote:
Fred, probably my previous post could/should have been clearer: I don't disagree with your findings, it's obvious to see which lens is better corrected and the comparison between two lenses of similar FL's makes sense. What I was trying to say is that to me AF matters (at least in that particular case) and hence no matter how excellent the 50 APO might be, it couldn't replace the 55 1.8 in my bag. Of course, this doesn't take anything away from the APO's excellent perfromance and I perfectly understand one would pick the CV over the 55 1.8, if AF isn't a major consideration. ...Show more →
tsdevine wrote:
I have an AF kit and a MF kit (with a couple crossovers.) Nothing wrong with keeping both and liking both.
I have two kits as well, Tim. You are right, of course, nothing wrong with owning and liking both. In an ideal world, it might own both . Alas, I don't need two 50mm primes and I'm in the process of slimming down my kit a bit.
There was a 'water fountain CA test' earlier on in this thread, and it seems a popular way to purportedly indicate colour correction. I came across this piece in a chat at TOP regarding the CV 65/2 APO lens. I have no way of knowing how relevant it is, but others may care to comment:
'The test described, shooting against backlit water droplets in a fountain actually makes me think that's not a good test, since I would think backlit water droplets would have a prismatic effect randomly distributed, and therefore *should* show color fringing..'
htt, if it's sharpness you seek in a 50mm, look no further. Except to add that it's not obvious edge sharpness, more like super resolution.
It's my sense from real world shooting that rear fall-off of edges is very rapid in the 50/2 and even at this level of magnification, it is apparent compared with the 55/1.8. Looking past the colour issues, see the line core is spreading fast in the APO-Lanthar with great evenness across the line motif.
The 55/1.8 retains the line core to the rearmost of the lines, soft but still clearly a line. Front bokeh looks similar in spread. It's a much better LoCA chart than the one used by Optical Limits. BTW, they described the 55's bokeh transition this way:
'the rendition in the critical focus transition zone is very smooth and buttery in the image background.'
What might they say about the 50/2? (They have never tested a modern E APO-Lanthar, like most other web review sites). Thanks for this one, very informative.
philip_pj wrote:
There was a 'water fountain CA test' earlier on in this thread, and it seems a popular way to purportedly indicate colour correction. I came across this piece in a chat at TOP regarding the CV 65/2 APO lens. I have no way of knowing how relevant it is, but others may care to comment:
'The test described, shooting against backlit water droplets in a fountain actually makes me think that's not a good test, since I would think backlit water droplets would have a prismatic effect randomly distributed, and therefore *should* show color fringing..'
I posted those water fountain photos. I don't pretend to be an expert on this subject, but what I can say is that the color shifting noted in the images was not randomly distributed in the images and was not "prismatic" in the sense that it contained the entire color spectrum. Perhaps I don't understand what you mean by "prismatic" and if that is the case, my apologies.
It probably isn't too easy to tell precisely where the focal plane on each image is given the complexity of the water drops and streams and ripples on the water, but I knew exactly where the focal plane was and could watch the colors shift as I moved the focal plane back and forth through the fountain. There was a definite magenta color cast for all reflections arising in front of the focal plane and a green color cast for all reflections arising behind the focal plane.
The images I posted are on Page 31, post #11. I might help if you could bring them up in another window while reading the comments below.
In the first photo I posted, the focal plane was located in the center of the fountain (where the arcs of the plumbing are farthest to the left). You can clearly see that the ripples in the water to the left of the plumbing are tinted magenta when in front of the focal plane and tinted green when behind the focal plane. A band of non-tinted water extends horizontally between them where the focal plane is located.
In the photo where the fountain looks green (the second image I posted), my focal plane was near the front edge of the fountain.
For the photo where the upper part of the fountain looks magenta and the water underneath the bowl looks green (the third photo I posted), my focal plane was roughly in the center of the fountain. The water that appears magenta was located in front of the focal plane and the water that appears green was behind the focal plane.
And there is no question that there is some degree of magenta and green fringing on some images of tree branches posted earlier in this thread. Not severe, but visible.
So I believe these color shifts represent Axial CA. But given the incredibly strong lighting and contrast in the fountain images I think the performance of this lens is actually excellent. I haven't really been able to provoke any significant Axial CA in any other shooting context.
IMHO, this lens is better corrected for CA (axial and lateral) than any other lens I have used and I certainly don't want anyone to draw the conclusion from the images that I posted that I think they represent a flaw in the way the lens handles CA. It is a stellar lens. I couldn't be happier with it.
If you have a polarizer, would it be possible to use that and do that water fountain test again? There are water fountains here but the Sun is sorely missing for a while.
If you guys are still looking for confirmation on whether or not there is any hint of chromatic aberrations, then — yes there is some in extreme conditions. I did previously post a fountain photo with zero aberrations, but that was an overcast day. The photo below is again an overcast day, but this time it's shot directly into the sun.
kind to the skin, p38 #17 - I was not expecting that in this lens, to be honest. I thought it would get by pretty well with people, but now I'm looking forward to coercing some more subjects into having their pictures taken. Great clarity, in fact that's the best word to me for it all - clarity.
It would be very interesting to see these images with all correction ON in C1 since that is the way the lenses will usually be used.The images with the corrections on will indicate the practical color differences in use.
