weekh wrote:
Whatever it is, it is CERTAINLY better than the ZF100 lens. The lens is also a great performer in its own right under such extreme backlite and high contrast situation.
No argument here at all. I know pretty well what the ZF 100/2 would have done to that ruler, and this lens clearly shows less colour. I just occasionally take opportunities to backpressure the "sensor blooming" meme, as it's typically applied to effects that are more readily explained by CA and the even more difficult to eliminate defocus colour (no formal name afaik).
Using a B&W ruler, this could have easily been adjusted in PP. How about posting the same shot with a standard wood ruler?
I've found the Zuiko 90/2, and Vivitar Series1 90/2.5, to be nearly APO-chromatic as well. If there is one thing I found lacking in the Cosina/Voigtlander 125/2.5 it is absolute sharpness, especially stopped down to my favorite macro apertures of f5.6-16. Wide open macro performance doesn't get any better than a good copy of the Zuiko 90/2.
cogitech wrote:
I've never seen purple LoCA before. Green? Red? Blue? Yellow? Yes.
Purple? No.
Not to mention, it happens in the sharpest area of the photo.
My guess is wee is correct.
Photozone didn't find any LoCA. It is APO-chromatic, after all:
pdmphoto wrote:
Wide open macro performance doesn't get any better than a good copy of the Zuiko 90/2.
Depends what you're looking for. Wide open, even at focus, there is some blue/purple left behind on the OM 90/2, and a considerable amount of green/violet as the colours go their separate ways upon defocus. In this measure it's outclassed (and similarly outpriced) by the Leica 90/2 APO-Summicron Asph.
Whether eliminating every last trace of colour, even at the expense of leaving, eg, some spherical, will depend on the intended use of the lens. For shooting specular highlights, probably it would be best to trade away absolute sharpness to eliminate CA. For typical macro applications, it's usually best to focus on the best resolution possible across a wide range of magnifications. Or spend the big bucks and get closer to having everything in one lens.
pdmphoto wrote:
Using a B&W ruler, this could have easily been adjusted in PP. How about posting the same shot with a standard wood ruler?
Why would Photozone.de fake the results of this test?
My own use of the lens has never shown any sign of LoCA, and I think the absolute sharpness of the CV is pretty obvious in just about every sample I have ever seen.
olyacme wrote:
Why would sharpness affect blooming, and why would blooming have a particular colour? .... If the "blooming" goes away, it never was blooming but rather either longitudinal or defocus CA.
I thought my point would have been obvious. If it is LoCA "and/or" defocus CA, then it would appear in the OOF areas of the photo, not the sharpest areas.
I think if we saw a crop of this image, we'd see that the purple fringe surrounds each entire highlight, rather than sitting on one edge as CA does (both CA and LoCA).
Well, just for pdm (and anyone else who might be interested) I've done some quick "testing" of various apertures on the Voigtlander.
The conclusion: From f2.5 through f11, the lens is ridiculously sharp. At f16, there is a slight (but noticeable) drop in resolution, but the results are what I would still call very usable.
cogitech wrote:
LoCA (Longitudinal CA) is extremely well-controlled, IMO:
Those are nice results and it's clearly a fine lens, but the test you used was relatively weak for discovering longitudinal CA. Chromatic aberration only refers to the focal plane. Defocus colour / bokeh CA or however photographers want to refer to it is a consequence of dispersion just like CA is, but just because a lens has eliminated lateral and longitudinal CA doesn't mean that all the colours reached the focal plane by the same paths. It means the final group has refracted different frequencies differently such that by the time they reach the focal they all line up. When the lens is brought slightly out of focus suddenly some colours can fail to stick with the pack and become apparent as they can spill into an adjacent dark area. At no point is light actually created or destroyed, of course, which is why a significantly out of focus area of a typical scene won't show defocus colour - everything is blended up enough to remain reutrally tinted.
A strong test for CA is to find a hard edge between the blackest black you can contrive, and a good strong white, and overexpose by multiple stops. Repeat slightly in and out of focus to check for defocus colour. Stars (and a tracking mount) are particularly effective for this test. Any colour that has managed to cross into an at focus dark area is CA. These conditions were approached by the backlit waves, and are why I strongly suspect that the so called blooming was in fact due to optical dispersion. It may have been an at-focus aberration, or it may have been due to defocus colour. The later aberration is not exclusive of a lens being legitimately labelled apochromatic, and even the former can be allowed under some definitions. Both of these effects typically diminish as a lens is stopped down, so it's very likely that the same scene shot with a smaller aperture would not show any colour, and blooming could be excluded.
I was curious if someone can post comparison shots between this CV125 and the Leica 100mm with the Elpro 1.2:1.1 converter.
I saw weekh had these two macro lens but he hasn't posted any comparison shots and looked to be going on vacation.
I am enjoying my used Leica 100mm and Elpro as it is very sharp wide open as well and I just love the Leica's colors.
olyacme wrote:
... I strongly suspect that the so called blooming was in fact due to optical dispersion. It may have been an at-focus aberration, or it may have been due to defocus colour.
Haven't we already established that it is not due to de-focus colour, since the blooming appears in the plane of focus (in wee's shot)?
I appreciate your response, but wee's photo looks like every other example of sensor bloom that I have ever seen.
Also, my test was intended to display the performance of this lens throughout the aperture range. It just so happened that there are a few very strong specular highlights in the OOF areas. If LoCA or defocus colour was going to show up, that's where it would show up. It didn't.
cogitech wrote:
Haven't we already established that it is not due to de-focus colour, since the blooming appears in the plane of focus (in wee's shot)?
Not necessarily. One of the critical strings of words in my primer was "slightly out of focus". To show defocus colour to its maximum the light cone should be sampled at such a point that the outlying colours neatly spill onto immediately adjacent sensels. This can stimulate red and blue, while leaving the remaining colours to "blow out" to neutral white, leaving the overall impression violet. Different colours may apply with different lenses or different conditions.
cogitech wrote:
I appreciate your response, but wee's photo looks like every other example of sensor bloom that I have ever seen.
I have seen this condition described as sensor bloom many times, but I have never seen a believable mechanical basis for this assertion. I'm especially troubled by the presence of a particular colour in the purported "sensor bloom".
cogitech wrote:
Also, my test was intended to display the performance of this lens throughout the aperture range. It just so happened that there are a few very strong specular highlights in the OOF areas. If LoCA or defocus colour was going to show up, that's where it would show up. It didn't.
Ideally you should undertake a star test, but it's also possible yours and wee's lenses differ. You miss the point, however. I am not trying to take away from this lens's performance. I wouldn't feel uncomfortable calling it a near apochromat based on what I've seen. But I would not feel comfortable asserting that apochromatic means no extraneous colour anywhere, or that "sensor blooming" is responsible for violet fringes.
olyacme wrote:
But I would not feel comfortable asserting that apochromatic means no extraneous colour anywhere, or that "sensor blooming" is responsible for violet fringes.
I can agree with that, as I don't know this lens inside out yet. I'd like to find more resources on sensor blooming, because everything I have ever seen/read indicates that violet/purple is how it manifests.
Just to be clear, the specular highlights in the third series of samples are flakes of chrome lit by full sun.
wayne seltzer wrote:
I was curious if someone can post comparison shots between this CV125 and the Leica 100mm with the Elpro 1.2:1.1 converter.
I saw weekh had these two macro lens but he hasn't posted any comparison shots and looked to be going on vacation.
I am enjoying my used Leica 100mm and Elpro as it is very sharp wide open as well and I just love the Leica's colors.
I've yet to see the Elpro available on Ebay or any resale market....
Does any know if you can use the different mounts such as OM, CY, Pentax or MD on a Canon FF using the appropriate adapter, or are there mirror issues? Will the lens have the same quality as the EF mount version?
I realize that electronic aperture control will be lost. Can aperture be controlled manually on the lens (other than EF mount).
ziyadj wrote:
Does any know if you can use the different mounts such as OM, CY, Pentax or MD on a Canon FF using the appropriate adapter, or are there mirror issues? Will the lens have the same quality as the EF mount version?
I realize that electronic aperture control will be lost. Can aperture be controlled manually on the lens (other than EF mount).
OM, C/Y, M42, K, F mounts can all be easily adapted and all include an aperture ring. I doubt that there would be any mirror issues adapting these versions of this lens.
