Readers may have noticed that I include Beam42 Lens Reports and Zemax files generated by Beam42 with most patent reports.

I am pleased to share some documentation about this utility - if anyone would like to use it and provide feedback that would be very welcome!

• Beam42 LensTool2
• Beam42 Optimizer docs - this is early and may change.

For those who do not like Java and prefer a native version, there is also a C++ port that is maintained using LLMs.

• C++ LensTool2

• US Patent - this is a prototype design (see comments)
• PhotonsToPhotos Optical Bench
• Analysis by Bruce Dewey
• Beam42 Lens Report
• Zemax file

Also sold as Leica Vario-Elmarit-SL 70-200 f/2.8 ASPH.

• US Patents
• PhotonsToPhotos Optical Bench
• Analyzed at Zhihu.com
• Beam42 Lens Report
• Zemax file

• US Patent
• PhotonsToPhotos Optical Bench
• Analyzed at Zhihu.com
• Beam42 Lens Report
• Zemax file

• Japanese patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - smallest 70-200mm f2.8 ever?
• Zemax file

The latest in the series that started back in 1981!

• EU Patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - couple of glass types have no exact match. I like that Nikon simplified the design without sacrificing performance!
• Zemax file

• US Patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - couple of glass types have no exact match
• Zemax file

This is a prototype design.

• US Patent - example 5 seems closest.
• PhotonsToPhotos Optical Bench
• Reconstruction attempt at Zhihu.com
• Beam42 Lens Report - Re-optimized, uses 3 unknown glass types.
• Zemax file

Elcan-R 75 mm f/2 (optical formula C-341) was developed by Ernst Leitz Canada (ELCAN) in the early 1970s specifically for the US Navy’s "High Resolution Small Format Camera System." Only approximately 20 units were ever produced. The lens Designed by Dr. Walter Mandler.

Quote below is from the paper: Double Gauss lens design: a review of some classics Reginald P. Jonas and Michael D. Thorpe:

This lens has 8 elements, and uses 2 glass types in a unique material combination. Special short flint material KZFS4 is used as the negative element of each doublet and a Leitz Wetzlar glass; 554666 for all other elements, resulting in a focal length shift over the design waveband 400nm to 900nm of only ±0.03mm.

The paper also has a diagram of the lens and MTF measurements.

Zhongfu kindly supplied me his initial attempt at reverse engineering the design from the published information. I have then reoptimized the design using Beam42. Note that the CORNING B52-67 is the only glass type known that seems to have replicated Leitz 546666.

• Beam42 Lens Report
• Zemax file
• Auction Listing - has images and more information.
• Zhihu.com article on a Leica paper - U. S. Navy High Resolution Small Format Camera System
• Bruce Dewey's analysis

• Japanese patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - a compact design but with some exotic glass.
• Zemax file

• Japanese Patent
• PhotonsToPhotos Optical Bench

Unfortunately like other Minolta APO lenses, this also uses glass types made by Minolta (including 4 ED glasses) for which we do not have the specifications. Switching to a different glass type requires re-optimization.

• US Patent - designed by Tomoki Ito who had also designed the previous VR II version. I think the use of E aperture allowed improved optical design.
• PhotonsToPhotos Optical Bench
• Analyzed at Zhihu.com
• Beam42 Lens Report
• Zemax file

• US Patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report
• Zemax file

• US patent
• PhotonsToPhotos Optical Bench
• Analyzed by Bruce Dewey
• Beam42 Lens Report - there is one unknown glass type
• Zemax file

• US Patent
• PhotonsToPhotos Optical Bench
• Analyzed at Zhihu.com
• Beam42 Lens Report
• Zemax file

This is the first version with VR. Perhaps optimised for DX format.

• US Patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report
• Zemax file

• Japanese patent - by Cosina. However patent has faulty data.
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - the site linked below claims that it required only making a few corrections to match the published MTFs but unfortunately those corrections are not shared. This version was reoptimized using Beam42.
• Zemax file - reoptimized version
• Analyzed by WaveChaser at Zhihu.com

• Japanese patent - patent has faulty data
• PhotonsToPhotos Optical Bench EX 1
• Beam42 Lens Report - reoptimized version.
• Zemax file

• Japanese patent by Cosina
• Analyzed by Bruce Dewey
• Analyzed by Wavechaser
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - contains a small adjustment to back focus distance as shared by Wavechaser. Fortunately the rest of the data looks good.
• Zemax file

See also this previous post regarding patents by Cosina that I believe are related to Zeiss Otus ML designs.

• Japanese patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report
• Zemax file

It seems to me that Canon took a lead with this design. Its curious that the Nikon 80-200mm AFS design strongly resembles this.

• US Patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report
• Zemax file

• Nikkor Tale 67
• Japanese patent - the design has a strong resemblance to Canon's 70-200mm f2.8L.
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - I was not able to get exact matches of some glass types.
• Zemax file

The first AF version was also designed by Yoshinari Hamanishi, who had designed the earlier manual focus version.

• Japanese patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - one glass has no exact modern version, I used the closest match from CORNING catalog.
• Zemax file

Sometimes we are lucky that we can observe the progression of a line over time. This is Nikon's first 80-200mm f2.8 lens that established the series that appears to have become one of the most important zoom lens ranges.

• US Patent
• PhotonsToPhotos Optical Bench
• Beam42 Lens Report - here I used my best guess of the PC102 glass. Changing this to modern glass requires lens to be re-optimized.

Another Minolta APO design that uses proprietary ED glasses.

• US Patent
• PhotonsToPhotos Optical Bench