Comparing macro lenses using MTF - part III - 0.66x

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RobertOToole
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Post by RobertOToole »

ray_parkhurst wrote:
RobertOToole wrote: Hi Ray, I think you switched the lenses by mistake, the 2x is not APO, at least my two samples were not even close, the 1:1 is APO at 1x from everything I have seen first hand.

I could have had two bad 75ARD2 units of course, that would explain the worst CAs of any lens in my 2x test ( and it was the only lens labeled APO).

Robert
I was not going by test results, but by the published curves. The 75ARD1 has two crossings in the focus vs wavelength curve, so by definition is not apochromatic. I can't actually remember if the apochromatic curve was for the 75ARD2, or the 120ARD. Wish I could find those curves!
Rodenstock does include LoCA correction in the PDF.

Image

ray_parkhurst
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Post by ray_parkhurst »

RobertOToole wrote: Rodenstock does include LoCA correction in the PDF.
Yes, it's there for the 75ARD1, and clearly shows the lens is not an apochromat. They don't show the LoCA curve for the 75ARD2 in the Qioptiq document.

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Post by ChrisR »

Ray - Senility may be a way off., yet ;)
It beats the 1x for LoCA. LaCA may be different of course.

Image

ARD 1x, ARD 2x and 120 are here http://www.filedropper.com/rodenstock
Chris R

ray_parkhurst
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Post by ray_parkhurst »

Excellent! Thanks for the docs ChrisR. But it's not exactly as I remembered...LoCA is better corrected but still not apochromatic, and neither is the 120. I thought I remembered that one of the 3 "apo" lenses was actually apo. Great to have the docs though!

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Post by RobertOToole »

The worst part is that these are calculated charts and not test results.

So these are ideal and a production lenses performance would be a certain % less. (this info was a reply from Rodenstock Germany to the US Rodenstock distributor)

The APO-Rodagon D 1:1 is designed for duplication so it looks like Rodenstock corrected for lateral CAs and not so much for LoCAs but they forgot about lateral CAs on the 2x and suppressed only LoCAs?

If the APO-Rodenstock D 2x is an APO lens than lenses like the Minolta 5400 and lots of others are really super-apochromats :D

RobertOToole
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Post by RobertOToole »

ray_parkhurst wrote:Excellent! Thanks for the docs ChrisR. But it's not exactly as I remembered...LoCA is better corrected but still not apochromatic, and neither is the 120. I thought I remembered that one of the 3 "apo" lenses was actually apo. Great to have the docs though!
In tests I posted here (they are on my site now) for the couple of lens samples I have the APO-Rodagon D 1:1 had no visible CAs at 1x (but it does show LoCAs). The 2x is another story entirely

:D

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Post by ray_parkhurst »

RobertOToole wrote:
ray_parkhurst wrote:Excellent! Thanks for the docs ChrisR. But it's not exactly as I remembered...LoCA is better corrected but still not apochromatic, and neither is the 120. I thought I remembered that one of the 3 "apo" lenses was actually apo. Great to have the docs though!
In tests I posted here (they are on my site now) for the couple of lens samples I have the APO-Rodagon D 1:1 had no visible CAs at 1x (but it does show LoCAs). The 2x is another story entirely

:D
It's odd that there are such discrepancies between the docs, your tests, my tests, and Miljenko's tests. I think this might be due to how we're interpeting our results, and differences in test methods, rather than sample variation. I personally have seen very little variation between the samples of 75ARD1 I have tested (>20 copies), but most all my tests are at 0.7:1, not 1:1. What I see is a very slight amount of both LoCA and LaCA on all samples. I have only tested ~5 of 75ARD2, again at 0.7:1 but also at 2.4x and at ~2:1, and have always seen very little CA. Perhaps there is more variation between copies of the 75ARD2 than 75ARD1?

RobertOToole
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Post by RobertOToole »

ray_parkhurst wrote:
RobertOToole wrote:
ray_parkhurst wrote:Excellent! Thanks for the docs ChrisR. But it's not exactly as I remembered...LoCA is better corrected but still not apochromatic, and neither is the 120. I thought I remembered that one of the 3 "apo" lenses was actually apo. Great to have the docs though!
In tests I posted here (they are on my site now) for the couple of lens samples I have the APO-Rodagon D 1:1 had no visible CAs at 1x (but it does show LoCAs). The 2x is another story entirely

:D
It's odd that there are such discrepancies between the docs, your tests, my tests, and Miljenko's tests. I think this might be due to how we're interpeting our results, and differences in test methods, rather than sample variation. I personally have seen very little variation between the samples of 75ARD1 I have tested (>20 copies), but most all my tests are at 0.7:1, not 1:1. What I see is a very slight amount of both LoCA and LaCA on all samples.
That might be it. Yes. I only tested the 1:1 lens at 1x and there in the corners looking at vertical lines at 200% there were no CAs. But Its hard not to miss LoCAs.

I think for best results its okay to compare results within a test but comparing test results between tests is a not the best idea, especially a image based test to one based on MTF. They are have pros and cons.

ray_parkhurst wrote: I have only tested ~5 of 75ARD2, again at 0.7:1 but also at 2.4x and at ~2:1, and have always seen very little CA. Perhaps there is more variation between copies of the 75ARD2 than 75ARD1?
I only tested 2 of these but CAs were the worst of the group behind even the Canon MP-35 and the Canon MP-E 65 which arent the best corrected lenses out there. But you are right about interpretation. Some people look at this and say "What CAs, where I see plenty, especially for a lens designated as APO :D

At 200%.

Image

R2=Rodenstock APO-Rodagon D 2x
C35= Canon MP-35
C65= Canon MP-E 65
SN7= Scanner Nikkor ED 7 element
M54=Minolta 5400
Opt=Optikos 106mm f2 - 2.82x

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Post by rjlittlefield »

RobertOToole wrote:Some people look at this and say "What CAs, where I see plenty, especially for a lens designated as APO
I can easily understand both positions. In isolation, the image at upper left would look fine to me, because I would assume that the colored lines are intrinsic to that unfamiliar subject. But knowing the subject, or in comparison with other images not having them, the colored borders are frighteningly obvious.

--Rik

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Post by ray_parkhurst »

RobertOToole wrote:
That might be it. Yes. I only tested the 1:1 lens at 1x and there in the corners looking at vertical lines at 200% there were no CAs. But Its hard not to miss LoCAs.

I think for best results its okay to compare results within a test but comparing test results between tests is a not the best idea, especially a image based test to one based on MTF. They are have pros and cons.

ray_parkhurst wrote: I have only tested ~5 of 75ARD2, again at 0.7:1 but also at 2.4x and at ~2:1, and have always seen very little CA. Perhaps there is more variation between copies of the 75ARD2 than 75ARD1?
I only tested 2 of these but CAs were the worst of the group behind even the Canon MP-35 and the Canon MP-E 65 which arent the best corrected lenses out there. But you are right about interpretation. Some people look at this and say "What CAs, where I see plenty, especially for a lens designated as APO :D

At 200%.

Image snipped

R2=Rodenstock APO-Rodagon D 2x
C35= Canon MP-35
C65= Canon MP-E 65
SN7= Scanner Nikkor ED 7 element
M54=Minolta 5400
Opt=Optikos 106mm f2 - 2.82x
I have trouble in a single image distinguishing LoCA vs LaCA. I am assuming these are LaCA, correct? Keep in mind that apochromaticity only refers to LoCA. A lens can have LaCA and still technically be apochromatic, though usually these seem to be corrected together.

Can anyone definitively state the color smears are LoCA or LaCA and why that is the case? I'd love to know for sure how to distinguish. When I am testing a lens, the two types are painfully obvious, but only in comparison between focal planes. LoCA shows up as a change in tint vs focal plane, while LaCA generally is independent of focal plane shifts, or at least this is what I see. Is it correct?

I find it odd that Rodenstock/Linos call the Apo-Rodagon D lenses apochromatic, yet are not afraid to show the data proving they are not. I guess that's just good marketing!

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Post by RobertOToole »

ray_parkhurst wrote:

I have trouble in a single image distinguishing LoCA vs LaCA. I am assuming these are LaCA, correct? Keep in mind that apochromaticity only refers to LoCA. A lens can have LaCA and still technically be apochromatic, though usually these seem to be corrected together.
Depends if you are talking about legal or formal, scientific (microscopy), or for consumer photography market.

Zeiss and Leica quote that an photographic APO lens is corrected so that the secondary spectrum is reduced so that the three colors are focused on the same image plane, but also that Lateral Chromatic Aberration, also known as “transverse chromatic aberration” corrected to the point where it is negligible.

So for Zeiss and Leica its both LoCAs and LaCAs.

Can anyone definitively state the color smears are LoCA or LaCA and why that is the case? I'd love to know for sure how to distinguish. When I am testing a lens, the two types are painfully obvious, but only in comparison between focal planes. LoCA shows up as a change in tint vs focal plane, while LaCA generally is independent of focal plane shifts, or at least this is what I see. Is it correct?
That sounds right.

For me, I usually look for color fringing along vertical edges near the borders as lateral or transverse CAs. LoCAs are easy to see in a stack looking at image thumbnails in a lightbox view as pink and green fringing.
I find it odd that Rodenstock/Linos call the Apo-Rodagon D lenses apochromatic, yet are not afraid to show the data proving they are not. I guess that's just good marketing!
I would guess those MTFs are for the industrial market since that is the market for the lenses.

Robert

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Post by Lou Jost »

When using a wafer as a test subject, can there really be any LoCA at a given point on the wafer if that point is in perfect focus?

ray_parkhurst
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Post by ray_parkhurst »

Lou Jost wrote:When using a wafer as a test subject, can there really be any LoCA at a given point on the wafer if that point is in perfect focus?
Doesn't each aberration have its own impact on CA? So while the 3 colors are in focus in the same plane, they may not line up geometrically?

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Post by rjlittlefield »

Lou Jost wrote:When using a wafer as a test subject, can there really be any LoCA at a given point on the wafer if that point is in perfect focus?
The point of LoCA -- "longitudinal CA" -- is that different colors do not focus at the same depth. So when a lens has LoCA, it is not possible for a point on the subject to be in perfect focus for all colors at the same time.

--Rik

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Post by rjlittlefield »

RobertOToole wrote:
Can anyone definitively state the color smears are LoCA or LaCA and why that is the case? I'd love to know for sure how to distinguish. When I am testing a lens, the two types are painfully obvious, but only in comparison between focal planes. LoCA shows up as a change in tint vs focal plane, while LaCA generally is independent of focal plane shifts, or at least this is what I see. Is it correct?
That sounds right.

For me, I usually look for color fringing along vertical edges near the borders as lateral or transverse CAs. LoCAs are easy to see in a stack looking at image thumbnails in a lightbox view as pink and green fringing.
Another useful distinction is that lateral CA appears as non-symmetric fringing, while longitudinal CA is symmetric or nearly so. For example if a dark line on bright background has green fringe on one side and magenta on the other, that will be due to lateral CA, but if the fringes are blue on both sides, that's due to longitudinal CA.

Longitudinal CA also commonly occurs even in the center of the image, while lateral CA does not. And longitudinal CA affects edges of all orientations, even ones that are perfectly radial.

In the wafer examples shown by Robert, the telltale clue for me is that the reddish fringes appear on both sides of a bright region against darker background.

--Rik

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