[New test photos released] Leica Summicron 35/2 Eight Element copy made in China

It is then a "similar lens". This is fine too. There is nothing special about being an exact replica. I expect to receive a lens from the first batch.
 
james.liam said:
Then it really isn't a replica. More of an homage.
Second round (if there is one), won't have elements of flint glass so it will be even less of a 'replica'.
Add multicoating and it's a whole other creature.
Click to expand...

james.liam, just by having newer lens elements and multicoatings you will get a change in the image. As far as I'm conserned, this lens is a Replica with improved light transmission. Kudos to a massive challenge that has been done right. Like I said before, I've had 4 Leitz Summarons from different years and different coatings, some amber, some cyan magenta. They all rendered slightly different with higher or lower contrast. Talking to friends I have who have worked in the Leitz factory, Hasselblad and Zeiss factories in Europe and I see face to face - lens designers can make "discretions" in the design decisions. In todays world, people are "focused" on the corner sharpness. If the lens design allows for an incremental adjustment of the field curvature and light transmission - then why not? There are so many variables. In essence, this lens looks just like the original Summicron. You can have confidence. If there is someone here who can give more detail on lens design, please do contribute.

As quoted from https://www.overgaard.dk/pdf/Leica-M-Lenses-Their-Soul-and-Secrets_en.pdf

"Every lens has certain characteristics, such as the type of glass, surface curvature (the radii of its two surfaces). These characteristics are called “parameters” or “degrees of freedom”. The theory states that each individual degree of freedom can be used for the
correction of an aberration. Conversely, every degree of freedom is also involved in all the aberrations. This means that the optical designer can assign aberration components to every individual surface.

The significance of the above can be explained by means of an example. This example is very important, because it demonstrates how an optical designer goes about his task and why creativity still plays such a large and decisive role in that task...

The optical designer must now decide how to correct these aberrations. He might try to change the curvature of the first lens in such a way as to reduce spherical aberration. But the curvature also determines the focal length, which should not be changed. It may also happen that a change in the curvature will reduce spherical aberration, but that the amount of coma will simultaneously increase. The designer may also choose to distribute the correction over several system parameters in order to reduce the likelihood of increasing other aberrations. When the task of correcting one particular aberration as much as possible is assigned to a single system parameter, there will be a problem in manufacturing if that very parameter is not within established tolerances. One could also find that, if tolerances are too tight, the manufacturing department may be unable of staying within those tolerances...."
 
Yes, I thought the whole idea of this lens was that they measured and copied the glass properties and curvatures precisely, so as to build a replica. The only differences are a) slighty larger diameter, b) substitution of glass type where no longer exactly available and c) guessing at coating formulae (and multicoating where customers requested it).
Differences between the new and original lenses probably result from these tiny differences and also from sample variations.
 
Hi Teddy and All,

Thanks for addressing my post regarding the field curvature and sharpness differences between the original and replica lens. No doubt in a lot of circumstances (especially landscapes), I look for edge to edge sharpness. Yet it other type of images (such as street and reportage)< I love unique characteristics in lenses and in the original 8 element which I used to own, I adored the exceptional sharpness and resolution in the center while it trailed off gently beyond the center as described. This signature and the extreme dichotomy between the center sharpness and edges is what drew me to the original 8 element in the 1st place (which I no longer own). At this early juncture, it appears the replica is different in this respect based on the posted test images. In some ways, its most definitely optically improved in many performance characteristics and in other ways, different as shown. I am excited to receive and use my replica but I now also know, that in ways shown, its both similar and different.

Dave (D&A)
 
Interesting results, Jose. A bit hard to see at the size posted on the forum above, but looking at the full size photos on your flick the original and replica do look quite similar to my eyes, more similar than I expected, with the replica showing a tad more field curvature in the extreme corners.

Regarding field curvature, I think designers of rangefinder lenses typically aim for a plane of focus that is close to flat or even curved inward towards the camera at the corners (helps in maintaining consistent focus when focusing and then placing the point of focus off center in the frame).

I'd guess that the original Summicron ended up with the field curvature it has because the lens designers back in the 1950s where chasing speed over flatness of field using the glass types available at the time (f2 was pretty fast for a wide angle lens back then).

I suspect the replica's field curvature is a side result of the optical glass types used rather than an intentional design decision. Unless you can make your own optical glass (something that not many manufacturers can do) or have the cash to commission a glass maker to make optical glass to your required refractive indexes, then you have to use glass that's available in the market and approximate as best you can. I think that's what the designers of the replica would have done (unless they have very deep pockets or direct access to an optics glass manufacturer) so my guess its that its not a replica down to the refractive indexes of each individual element, but instead a very close approximation using the glass types that were available to them. And a damn good one too. The replica's level of detail is really quite amazing considering that the manufacturer is not one of the big boys in the industry.

james.liam said:
Then it really isn't a replica. More of an homage.
Second round (if there is one), won't have elements of flint glass so it will be even less of a 'replica'.
Add multicoating and it's a whole other creature.
Click to expand...

Light Lens Lab stated ages ago that the replica is not an exact copy, and was never intended to be.
 
D&A said:
Hi Teddy and All,

Thanks for addressing my post regarding the field curvature and sharpness differences between the original and replica lens. No doubt in a lot of circumstances (especially landscapes), I look for edge to edge sharpness. Yet it other type of images (such as street and reportage)< I love unique characteristics in lenses and in the original 8 element which I used to own, I adored the exceptional sharpness and resolution in the center while it trailed off gently beyond the center as described. This signature and the extreme dichotomy between the center sharpness and edges is what drew me to the original 8 element in the 1st place (which I no longer own). At this early juncture, it appears the replica is different in this respect based on the posted test images. In some ways, its most definitely optically improved in many performance characteristics and in other ways, different as shown. I am excited to receive and use my replica but I now also know, that in ways shown, its both similar and different.

Dave (D&A)
Click to expand...

Well, these are all fine and reasonable thoughts, as well as james.liams comments that I take within reason. In the final picture of things however, if you decide to print or view an image rendered with this Replica lens, it will look essentialy the same.

In my own point of view, I decided to get this lens if certain criteria was met, and that is: it's all brass and like the original (actually the original is part alu part brass), the coma and veiling flare in the corners are the same, the depth of field and specular highlights are the same, the out of focus rings are the same, the resolution and chromatic aberrations are the same.

I can confidently conclude that all of the above are just that in my copy. In regards to chromatic aberrations, there are NONE and this is a deal braker for me. This is excellent. When it comes to Depth of Field and Curvature of Field - it has been decreased by a very small margin in improvement of what it seems, corner sharpness. This is welcomed.

In essence, it is the same as the original when it comes to the printed image. We are dealing with marginal hair differences.
 
jonmanjiro said:
Regarding field curvature, I think designers of rangefinder lenses typically aim for a plane of focus that is close to flat or even curved inward towards the camera at the corners (helps in maintaining consistent focus when focusing and then placing the point of focus off center in the frame).

I'd guess that the original Summicron ended up with the field curvature it has because the lens designers back in the 1950s where chasing speed over flatness of field using the glass types available at the time (f2 was pretty fast for a wide angle lens back then).

I suspect the replica's field curvature is a side result of the optical glass types used rather than an intentional design decision.
Click to expand...

All your comments are quite sound jonmanjiro, I agree. I have this lens now and I applaud all the effort that has gone into it. I have confidence in it and hopfully LLL can make another Replica project. I'm in.
 
Teddy, I concur with your last post. Please keep in mind, I can only comment on my subjective feelings regarding the original vs the replica based on the posted web sized images here. I long ago ascribed to the standard that its prints that I that characterize the performance of a lens and from what you say, both versions are extremely close with the replica emulating the replica. I can see how web images might deviate a bit from this while the printed images show a very close and near identical performance and characteristics between the two lenses.

Again let me state, as other have done, that accolades are due to those who designed and manufactured the replica. a tremendous amount of credit is owned to them for their efforts.

Dave (D&A)
 
Just a thought, even though I didn't personaly know Mr. Abrahamsson, but I wonder what he would have thought of this Replica - for those who knew him?

I enjoyed and miss his comments here on RFF.
 
Interesting you should mention Tom A, Jose. I was thinking about him as I wrote my last comment! Cosina is one of those lens manufacturers than can/does make their own optical glass, and from the stories Tom A told me, I know he enjoyed tossing engineering problems at the lens designers to figure out, even if it meant coming up with new types of optical glass. I'm quite certain Tom A would have been very impressed by this replica.
 
Tom Abrahamsson and I were quite close friends for the last 20 years of his life. We spoke about all sorts of equipment, and especially lenses, when we were together. I do not recall ever having a conversation about the 8-element, however. Perhaps some else here had such a conversation with him, or there is something in another thread here.

He did tell me that he had a special 35/1.4 first gen, which had been picked out by Dr. Mandler, I think, for its enhanced performance wide open. I never got a chance to shoot that lens, so I know little more. Tom also went on about the Nikon RF 35/1.8, and the 35/2.5 which helps felt was a superior lens overall. He had a special shade made for the 35/2.5, which fit the 35/1.8 in LTM, and which I have right next to me here as I write.

Of course Tom was excited about the 35mm lenses that Cosina made, and hand me try whichever one was the latest offering the very last time we met (I don't recall the exact lens).

I do think Tom would have significantly appreciated what Mr. Zhou is doing, and liked the result. I think that we would have heard quite an earful about this, if he only was still here. I miss Tom terribly.
 
Field curvature is influenced by the sensor cover glass. It is flat, but its optical properties are different from air that would be there in front of film. At the center, the light hits it at a different angle and has a shorter way to travel through the glass than in the corners. I'd like to see more tests on film, those posted by jonmanjiro a little while ago don't show this corner thing so clearly.
Regarding the question of how precise a copy it is, I wonder if the maker could get exactly the same sorts of glass or just very similar ones and then adjusted the lenses accordingly...?
 
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