90mm APO 1990's vs 2020's - any difference?

[Tseg]

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The 90mm APO Summicron was launched in the 1990's.  Now, a quarter of a century later, the same model number is being sold in market.   I recently bought one, made in 4Q2024, and am wondering if there are any performance differences from the 1990's models, beyond adding 6-bit coding?  I believe Leica produces their own APO glass and I'm wondering if that formulation may have been improved in the past few decades?   Anyone have knowledge or actual comparisons of the then and now versions of this lens?

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[FrozenInTime]

Many pre-6 bit 90mm APO lenses could not hold f/2 rangefinder tracking across the full focus range. 

Sorry no experience of later lenses; changed to the 75mm Summicron, which is a lot better, but still a challenge to focus due to the short focus throw.

[Tseg]

52 minutes ago, FrozenInTime said:

Many pre-6 bit 90mm APO lenses could not hold f/2 rangefinder tracking across the full focus range. 

Sorry no experience of later lenses; changed to the 75mm Summicron, which is a lot better, but still a challenge to focus due to the short focus throw.

I do notice that closer-focusing at f2 is all but impossible without using a Visoflex 2, if that is what you are referring to?  This is with my recently made lens.

[FrozenInTime]

19 minutes ago, Tseg said:

I do notice that closer-focusing at f2 is all but impossible without using a Visoflex 2, if that is what you are referring to?  This is with my recently made lens.

Mine was perfect at 1m, but hopelessly back focussed by 3m.

This old thread has some background https://www.l-camera-forum.com/topic/126705-please-advise-on-my-90mm-summicron-woes/

[lct]

No difference i'm aware of but as far as focusing is concerned, i would favour a lens made or adjusted in the digital era. My coded 90/2 apo is spot on for instance but my uncoded 90/2 v3 needed to be calibrated for digital.

[Tseg]

I won't bore you with all my test pics I just took, but I just took dozens of pics using a tripod with 2 sec delay from close focus to infinity.   First, I determined my B+W Clear MRC filter adds purple fringing near infinity (or for these specific shots, near infinity, but not closer), but there remains very slight purple/green fringing when pixel peeping without a filter at infinity.   Second, my 90mm does focus through the OVF perfectly up until near infinity... after ~25ft. my pixel-peeping hyper-focal becomes very slightly front focused (I have to move the OVF focal distance out <1mm on the ring to achieve hyper-focus).    

In summary, my initial observations about close focus f2 issues were unfounded... my technique was clearly lacking.    At distances under 20ft the OVF seems well calibrated with this lens.   At near-infinity, pixel-peeping reveals some very slight near-focusing, but I think unrecognizable for practical purposes.  I think my "focus" concerns should be more focused on camera stabilization than OVF/lens misalignment... for a 90mm APO lens built in 4Q2024.  I also need to rethink the "value" of having B+W Master Clear MRC filters on all my lenses for protective purposes.

This image was taken at over 25', with with a very slight lean further out on the focus ring...  The focus object was this infinity logo on the speaker.  64 ISO, f2,  1/8 sec. tripod. 2 second delay.  Pixel peeping and uncropped SOOC.

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[Robert Blanko]

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I was looking for a used 90 APO summicron some months ago in a Leica store and asked the shop attendant whether the version (I think, built before 2000) had any differences as compared to the current APO. He answered that likely the coating is not optimized for the digital era: the back-reflections from the sensor that were not present in the film era could possibly not be handled similarly well as in the current version.

This is why I refrained from buying an old version so far. No idea though whether the information is just hearsay or really reliable. But at first glance, it appeared plausible to me.

[graphlex]

Back in 1999 I got one of these at wholesale through the good offices of a Leica ‘insider’ (exec at a vaguely related company).  
He mentioned that this lens was (then) being made for Leica Camera by the old ELCAN defense contracting business (later=Hughes Aircraft, still later=Raytheon).

it was brutally sharp, but less so at portrait distance. Nevertheless, it was too sharp for a picture of anyone the photographer wanted to stay on friendly terms with.

It was breathtakingly good at f/2 focused at infinity, a very useful thing for low-light landscapes on Kodachrome or Velvia.