90mm Apo-Summicron-M not apochromatic?

[LarsHP]

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11 minutes ago, farnz said:

I think this is where your problem lies: expectation.  There is no formal standard for LoCA corrected performance in lenses so it's a subjective 'performance standard' that you've created based on subjective performance of other unconnected lenses.

Clearly from your opening post the lens exhibits some performance features that appeal to you so the lens has value to you.

If the LoCA performance is unacceptable to you then you should send the lens to Leica with details of what you're not happy with backed up by pictures.  You might not want to be without the lens for a period of time and you might not wish to pay the price of shipping, inspection, and any adjustment that might be required - that is your decision.  Alternatively, you might decide that it is better to save your money and fix any unacceptable LoCA in post-processing.

Whichever you choose I wish you luck.

Pete.

 

Right. My expectation for a Leica lens with the apo designation is that LoCA is reduced to a minimum, and that when looking at lenses without the apo designation, it will perform better. However, it doesn't seem to do so (regarding LoCA) which is where apo lenses usually excel. LaCA can often easily be corrected in post processing, so that's not as important as LoCA. 

After thinking about it, I think all modern lenses from the major lens producers live up to the definition of  beings apochromatic in the plane of focus. If not, we would see blurry images where it is supposed to be in focus. Standard black and white test charts may show LaCA (red on one side of the edge and cyan on the other), but I don't recall seeing color fringing around the edges of these B&W targets. This would be the case if one of the RGB channels isn't in focus, I think. Or perhaps I am wrong here?

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[jaapv]

Apochromatic correction means coincidence of the light rays in the focal plane at infinity on three points of the visible spectrum. Leica uses four. What happens between these points  is not defined. That a lens is apochromatically corrected in the center does not necessarily mean that it applies towards the edges and corners.  Achromatic means coincidence at two points 

[LarsHP]

10 minutes ago, jaapv said:

Apochromatic correction means coincidence of the light rays in the focal plane at infinity on three points of the visible spectrum. Leica uses four. What happens between these points  is not defined. Achromatic means coincidence at two points 

So, if the lens has no floating element and thus no close focus correction, then the lens won't be apochromatic at closer distances? (This sounds like the 90 apo.)

[pedaes]

16 minutes ago, LarsHP said:

So, if the lens has no floating element and thus no close focus correction, then the lens won't be apochromatic at closer distances? (This sounds like the 90 apo.)

I think we are going round in circles here.

If it helps, this is a picture I took last week with M10. You can see if this demonstrates what you are concerned about, I am very happy with the lens.

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[jaapv]

20 minutes ago, LarsHP said:

So, if the lens has no floating element and thus no close focus correction, then the lens won't be apochromatic at closer distances? (This sounds like the 90 apo.)

May not be.. You’d need to measure it to know. 

[lct]

1 hour ago, LarsHP said:

So, if the lens has no floating element and thus no close focus correction, then the lens won't be apochromatic at closer distances? (This sounds like the 90 apo.)

It such a case it should show purple fringing on close ups, which i have never seen so far. Here on full frame at f/2. I suspect your problem came from overexposure (snow?) but i may be wrong.

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Edited May 16, 2021 by lct

[jaapv]

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13 minutes ago, lct said:

It such a case it should show purple fringing on close ups, which i have never see so far. Here on full frame at f/2. I suspect your problem came from overexposure (snow?) but i may be wrong.

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You’d need edges with 100% contrast to have it show up. Anyway,as easy as LaCA to remove by the purple/blue slider. 

[LarsHP]

Here is the crop from the image in the OP + one shot with my Nokton 50mm f/1.2 Asph. Both are shot @ f/2, are in 100% (from 24MP files) and without lens profile corrections.

As you can see, the apo designation isn't visible when comparing the Apo-Summicron-M to the superfast Voigtländer f/1.2 lens at the same aperture. I checked the brightest areas of the snow in Photoshop and the values are around 230 (max is 255) for all three RGB channels. In other words, the highlights are far from overexposed. (For reference, I didn't use the highlight recovery slider, and no exposure correction either.)

Here are two links to reviews of "apo"-lenses where the LoCA is very well corrected. I might do a similar LoCA test with my 90 Apo and post it here.

https://www.lenstip.com/388.5-Lens_review-Carl_Zeiss_Apo_Sonnar_T*_135_mm_f_2.0_ZE_ZF.2_Chromatic_and_spherical_aberration.html

https://www.lenstip.com/517.5-Lens_review-Voigtlander_Apo-Lanthar_65_mm_f_2_Aspherical_1:2_Macro_Chromatic_and_spherical_aberration.html

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[LarsHP]

2 hours ago, pedaes said:

I think we are going round in circles here.

If it helps, this is a picture I took last week with M10. You can see if this demonstrates what you are concerned about, I am very happy with the lens.

 

Great shot! What aperture do you use?

BTW: You did read in my OP that I consider the lens great for near infinity shooting where LoCA isn't an issue?

Here's a test shot in full resolution wide open and without lens corrections and moderate contrast and sharpening settings:

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[lct]

Interesting thank you but i can't seem to see any purple fringing on my screen. Would you mind to post crops of your Leica pic where such fringing is obvious?

[LarsHP]

9 minutes ago, lct said:

Interesting thank you but i can't seem to see any purple fringing on my screen. Would you mind to post crops of your Leica pic where such fringing is obvious?

It's readily visible in the crop of the shot I posted in the original post, side by side with green fringing. 

Edited May 16, 2021 by LarsHP

[lct]

1 minute ago, LarsHP said:

It's readily visible in the crop of the 90mm shot I just posted, side by side with green fringing. 

So no purple fringing then, right? As for green fringing i seem to see some of it on both pictures the Leica one being more contrasty. Is that the issue you were referring about? Just curious.

[didier]

15 hours ago, farnz said:

Apochromatic lenses are designed to precisely overlay three wavelengths (usually in the red, green, and blue wavebands) in the plane of focus.  But the plains and island that you mention are in out of focus areas where it's not reasonable to expect the three wavelengths to coincide perfectly owing to chromatic dispersion, ie the difference in the velocity of propagation of different wavelengths through glass.  The three colours will travel through the lens differently so when the rays pass the plane of focus they will spread differently and not coincide precisely in the out of focus areas.

Pete.

Exactly ! thanks Pete.

even the mighty ‘lux SL 50 does show chromatic aberration in the OOF areas in such situation 

[LarsHP]

1 hour ago, lct said:

So no purple fringing then, right? As for green fringing i seem to see some of it on both pictures the Leica one being more contrasty. Is that the issue you were referring about? Just curious.

Yes. Purple fringing visible in the crop in the image of the original post and the first image in post #28, which is a 100% crop of it. Check the plains with snow and earth mixing (in the lower part of the image). Mostly green fringing, but also some purple. The purple fringing actually puzzles me.

Just to make it clear: the image I linked to in post #29 (the tilted landscape with trees and clifs in snow) does of course not show LoCA since everything is in focus. What the image shows is the "upside" of the 90 apo's performance: zero LaCA, minor field curvature and good sharpness in almost the whole frame even wide open. 

[lct]

First image, you mean this one?. If so i don't see any purple fringing in there and neither do i in that of post # 28. I wonder if you (or i?) know how purple fringing can look like but anyway you don't need my help here do you so i will let you discuss with others if you don't mind .

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[LarsHP]

Maybe the correct term isn't "purple fringing", but purple (in addition to mostly green) "chromatic aberrations" or "bokeh fringing". I'm fine with whatever you call it. 

Edited May 16, 2021 by LarsHP

[leicameech]

I have to say I think this is a very entertaining thread! But LarsHP, you did inspire me to check some specs, because I tend to agree with pedaes -- get rid of the thing and forget about it. However, just in the spirit of having some fun, I would like to point out a couple of things: 

Remember that the Leica 90 APO-M weights 500g. The 65 Voigtlander is 625g and bigger than the 90 APO-M. The 90 APO-SL weighs 720g. The 135 f/2 Zeiss you're comparing your 90 APO to weighs 920g. Both lenses (Zeiss and Voigtlander) are very impressive, of course. They also don't exist in M mount though, and if the Voigtlander 65 APO performs better than either of their current M mount APO lenses (I don't know, but that would be interesting to learn), then it's not really a fair comparison. If Voigtlander can just whip up a 65 APO and have it be better than Leica's $5k 90 APO then why wouldn't they just do that in M mount too? All reviews I've seen of the Voigtlander APO 35 and 50 M mount lenses have been "it's 95-99% as good as the Leica, and wow, what a great price." I've yet to hear anyone say that they'd choose the Voigtlander over Leica's 35 or 50 APO if money were no object. The opposite is true in the case of the f/1.4 Distagon ZM over the 35 FLE Leica, however. Many tend to say that the Zeiss is the better lens optically, but the size of it turns them off. Or it doesn't and then the Distagon users are as happy as can be (I really want that lens, by the way). Is anyone choosing the 135 f/2 Zeiss or 65 APO Voigtlander over the 90 APO-M Leica? They're three totally different lenses!

Rangefinder Leica lenses, the modern "high-performance" ones anyway, are not (quite) perfection. They're as close as it gets given the size constraints and the system they're designed to be shot on which, by virtue of its design, is not that precise to begin with. We're talking about a system that you can only focus in the center of the frame on here, in 2021, where you can spend a lot less on a camera that does much more (SL, Sony A7, Fuji MF, the list goes on..). Do the ol' focus and recompose, and at close distance with the 90 APO your focus point is off every time anyway. Then you compensate by doing the rangefinder lean forward/back and learn a bunch of weird techniques to nail focus with a digital rangefinder. Or get a Visoflex and turn your M into an overpriced SL without most of the SL's advantages. 

We're talking about a lens for a system that is unnecessarily complicated given current technology. And the lens is still amazing. And built like a tank. And gorgeous. I still don't get what you're looking for that it's not delivering! For the price, the 90 APO-SL is the better "value" if absolute perfection is what you're looking for that can (likely) beat the two lenses you've thrown in for comparison.

TL;DR: If you're disappointed with what Leica's "APO" designation represents based on your results with this lens, take a look at the 90 APO-SL. If you're testing to see if Leica is worth the money, may I suggest you take a look at a thread I wish I could be making contributions to -- the 50 f/1.2 Noctilux image thread. You will be appalled at what Leica's ASPH designation can mean 

 

[LarsHP]

2 hours ago, leicameech said:

I have to say I think this is a very entertaining thread! But LarsHP, you did inspire me to check some specs, because I tend to agree with pedaes -- get rid of the thing and forget about it. However, just in the spirit of having some fun, I would like to point out a couple of things: 

Remember that the Leica 90 APO-M weights 500g. The 65 Voigtlander is 625g and bigger than the 90 APO-M. The 90 APO-SL weighs 720g. The 135 f/2 Zeiss you're comparing your 90 APO to weighs 920g. Both lenses (Zeiss and Voigtlander) are very impressive, of course. They also don't exist in M mount though, and if the Voigtlander 65 APO performs better than either of their current M mount APO lenses (I don't know, but that would be interesting to learn), then it's not really a fair comparison. If Voigtlander can just whip up a 65 APO and have it be better than Leica's $5k 90 APO then why wouldn't they just do that in M mount too? All reviews I've seen of the Voigtlander APO 35 and 50 M mount lenses have been "it's 95-99% as good as the Leica, and wow, what a great price." I've yet to hear anyone say that they'd choose the Voigtlander over Leica's 35 or 50 APO if money were no object. The opposite is true in the case of the f/1.4 Distagon ZM over the 35 FLE Leica, however. Many tend to say that the Zeiss is the better lens optically, but the size of it turns them off. Or it doesn't and then the Distagon users are as happy as can be (I really want that lens, by the way). Is anyone choosing the 135 f/2 Zeiss or 65 APO Voigtlander over the 90 APO-M Leica? They're three totally different lenses!

Rangefinder Leica lenses, the modern "high-performance" ones anyway, are not (quite) perfection. They're as close as it gets given the size constraints and the system they're designed to be shot on which, by virtue of its design, is not that precise to begin with. We're talking about a system that you can only focus in the center of the frame on here, in 2021, where you can spend a lot less on a camera that does much more (SL, Sony A7, Fuji MF, the list goes on..). Do the ol' focus and recompose, and at close distance with the 90 APO your focus point is off every time anyway. Then you compensate by doing the rangefinder lean forward/back and learn a bunch of weird techniques to nail focus with a digital rangefinder. Or get a Visoflex and turn your M into an overpriced SL without most of the SL's advantages. 

We're talking about a lens for a system that is unnecessarily complicated given current technology. And the lens is still amazing. And built like a tank. And gorgeous. I still don't get what you're looking for that it's not delivering! For the price, the 90 APO-SL is the better "value" if absolute perfection is what you're looking for that can (likely) beat the two lenses you've thrown in for comparison.

TL;DR: If you're disappointed with what Leica's "APO" designation represents based on your results with this lens, take a look at the 90 APO-SL. If you're testing to see if Leica is worth the money, may I suggest you take a look at a thread I wish I could be making contributions to -- the 50 f/1.2 Noctilux image thread. You will be appalled at what Leica's ASPH designation can mean 

 

Thanks for contributing to the discussion. I think you issue several points that are valid, including the size, weight and mount of the lenses I compare the M 90 apo to. These lenses are of course not designed for Leica M cameras, but DSLR or mirrorless. If Voigtländer or Zeiss had made a 90mm f/2 Apo-Lanthar or Apo Sonnar in M mount that were close to the counterparts above, then I probably would have just bought one of those, but they haven't. (I use M mount lenses for their small size and moderate weight while covering full frame and maintaining a high optical quality.)  

For instance, the focal length of the 65mm Apo-Lanthar makes it incompatible with the rangefinder system, so it would not make sense making it in M mount. (Hopefully Voigtländer will make it in Z, L and RF mount soon.) The 135mm Apo Sonnar has a compatible focal length, but its size will make it unusable with the rangefinder too. I addition the weight doesn't appeal to the Leica M system ideal of compact and light lenses. 

The reason I made reference to them is because they are true apochromatic lenses in the usual sense, meaning that LoCA is greatly reduced or absent. This is were my disappointment with the M 90 apo is. It performs pedestrian in that regard. My Elmarit-M has about the same degree of LoCA as the so-called "Apo" lens. (Sorry if insulting the Leica company and fanboys thereof). As mentioned in a previous post, if Leica had called the lens "90mm Summicron-M Asph", then there would be no reason to be underwhelmed or disappointed. In other words, my criticism and disappointment with the performance of the lens is related to the discrepancy between what Leica say it is and what it actually is in terms of optical performance. (As I wrote above, I think all modern quality lenses have three colors focused in the plane of focus, so saying a lens is apochromatic must imply that such a lens controls CA better than other non-apo designated lenses.)

Regarding your comments on the M cameras and focusing, this is one of the reasons I don't use a Leica M camera with my M lenses. Another is the lack of image stabilization (IBIS). I have gone the odd route and sent my Nikon Z6 to Kolari Vision who removed the stock sensor glass and replaced it with an ultra-thin one thus getting the same sensor stack thickness as Leica M sensors have which means wide angles perform comparably on the UT converted camera as on a M camera. (Compared to a M 240 my Z6UT has practically no "Italian flag" issue with my 28mm Summicron-M Asph II, but does vignette a bit more.) 

Edited May 17, 2021 by LarsHP

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[pedaes]

12 minutes ago, LarsHP said:

I don't use a Leica M camera with my M lenses.

Geez - what is this all about? Use the lenses that give you what you want. For the record, the APO-90 Summicron is a APO lens. Think your issue comes not from the lens.

[LarsHP]

4 minutes ago, pedaes said:

Geez - what is this all about? Use the lenses that give you what you want. For the record, the APO-90 Summicron is a APO lens. Think your issue comes not from the lens.

At present, I don't think there is a 90mm f/2 lens in M mount which is better. I may have to check out the 75mm apo instead. 

Regarding the "issue comes not from the lens" we agree in a way. As I wrote, it's the apo designation that I criticize based on the level of LoCA. It does control LaCA very well though.