How Leica Bayonetted its Customers Without Screwing Them:
The Curious Ins & Outs of Leica Screw-to-M-Mount Adapters
By Jason Schneider
The Leitz screw-to-M-bayonet adapter, introduced at the time of the Leica M3’s official debut in 1954, lets you mount virtually any Leica screw mount (LTM) lens on a Leica M body, retaining full functionality and precise rangefinder coupling. Elemental and ingenious, the M-mount adapter is a stunning example of non-obsolescence that demonstrated Leica’s commitment to its loyal customers who had purchased thousands of screw mount Leicas and LTM lenses as far back as 1930. The adapter certainly contributed to the success of the Leica M series and even allowed Leica to evolve the Barnack Leica, culminating in the magnificent Leica IIIg of 1957-1960.
Willi Stein, "Father of the Leica M3" left, and Hugo Wehrenfennig, designer of the M-mount system, right.
The man who devised the simple but sophisticated Leica screw-to-M-mount adapter was Hugo Wehrenfennig, the same brilliant mechanical engineer at E. Leitz, Wetzlar who designed the iconic 4-lobed bayonet M-mount. It was his idea to reduce the flange focal distance (FFD) of the Leica M system to 27.8mm, 1mm shorter than the 28.8mm distance from the lens flange to the film plane in previous (screw mount) Leicas. This small difference made it possible to use screw mount lenses on Leica M cameras by means of thin bayonet adapters with an effective “extension factor” of 1mm while maintaining infinity focus and without compromising the optical or mechanical performance of the lens.
Often taken for granted, the screw mount to M adapters were an essential part of the Leica rangefinder system. Allowing backward lens compatibility to the first standard mount screw mount lenses in 1930, these ingenious adapters kidnapped hundreds of thousands of Leica Barnack owners into the Leica M camera club as they screamed in protest over the “outlandlishly huge and heavy” (to them) M3 camera body. Without Barnack owners’ eventual support of the M system, there’s little doubt that the M camera series would have been much less commercially successful. The Leitz screw mount to M adapter was also an important first in 35mm rangefinder camera history. It was probably the first time a new rangefinder mount was made backwardly compatible with older lenses of a different mount. Hugo deserves his own statue beside Oskar Barnack and Hektor, Max Berek’s dog.
Page 86 on M-mount Adapters from James Lager's authoritative Volume III on Leica Accessories, in his monumental series An Illustrated History of Leica.
Copy of James Lager's Leica Viewfinder article on M rear lens caps with "feet" for removing stuck M adapters. Feature was later dropped.
The first three M adapters were Leica code named IRZOO (50mm), ISBOO (90mm) and ISOOZ (135mm), corresponding to the 3 frame lines in the Leica M3. They are auto-indexing, meaning they keyin the proper viewfinder frame line for their marked focal length when the adapted lens is mounted on the camera. The earliest Leitz adapters were engraved with the serial number of the lens it was matched to, and a “job number” on the back to link it to the original order, but both systems were phased outby the late 1950s. Many original Leitz rear M caps have 3 tiny tabs or feet on the back that fit into the notches on M adapters, allowing the cap to be used as a tool to remove an adapter if it gets jammed in the M mount. Evidently this wasn’t a common enough problem, so this feature was later dropped.
Types of screw mount to M adapters from James Lager's iconic Illustrated History of Leica, Volume III, page 87.
Originally, all Leica M adapters, whether made by Leitz or by third parties such as Novoflex, Kilfitt, and Komura, were marked with a single focal length, 28, 35, 50, 75, 90 or135mm. But since the advent of the M6 in 1984 (which displayed 28mm & 90mm, 35mm & 135mm and 50mm & 75mm frame lines in pairs) newer adapters now have dual focal length designations. To ensure backward and forward compatibility, all later Leica M models usethe same system used on the original adapters, so if you have an M adapter made in 1954 it will still work perfectly on a 2022 MP. The only difference is that the 50mm adapter also brings up 75mm frame line, the 90mm adapter also brings up 28mm frame line.and 135mm also displays the 35mm frame line, even though none of these secondary frame lines were available on the M3. Brilliant! Result: with only 3 vintage or modern LTM-to-M adapters you’re golden. And if you’re shooting with an M-mount Voigtlander, which has manually selected viewfinder frame lines, all you need is a single M adapterof any type (Voigtlander made them)—so long as you don’t mind switching it among your screw mount Leica lenses.
Leica stopped making LTM-to-M adapters decades ago but they’re still readily available from independent companies including FotodioX, Metabones, Rayqual and several unnamed Chinese companies, Since they’re essentially a one-time forever purchase I’d go for quality. Generally, the less you pay the more likely you are to waste your time on out of focus pics.
Leitz, New York Product Directory of 1954 listing the new Leica M3 and its many accessories, including M adapters.
Listing for first 3 Leitz screw-to-M-mount adapters in 1954 Leitz, New York Catalog--not bad at $10.50 apiece!
Essentially LTM-to-M adapters come in 3 types, informally designated as Type 1, Type 2, and Type 3.
Type 1 refers to the various pre M8 adapters without indents for digital M lens bar coding, whether made by Leica or any 3[SUP]rd[/SUP] party manufacturer. The key identifier is no indents on the back of the adapter for adding lens bar coding. Please note that Leica’s lens bar coding is patented and apparently not licensed to other lens or camera makers. Therefore, Leica’s M bar coding is only readable on digital M cameras or other adapted Leica digital cameras. Type 1 adapters for 35mm or 50mm lenses are thinner at the bottom, the cutaway providing clearance for the push-in, spring-loaded infinity catch on the focusing tabs found on the following Leica lenses: 35mm f/3.5 Elmar, 35mm f/3.5 Summaron, 50mm f/3.5 and f/2.8 Elmar, and the collapsible 50mm f/2 Summar, Summitar, and Summicron. Type 1 adapters are perfectly usable for film M mount cameras of any manufacture, only being limited for digital M cameras.
Type 2 adapter key identifier is the indents on the back of the adapters for adding bar coding, but they do not have the thin area or cutout at the bottom to accommodate infinity catch lenses. How do you add bar coding? Very Carefully! Various coding kits are available on eBay to make the job easier. Black enamel model paint seems to be the preferable painting medium. Again, take note: bar coding is useful only on digital M and other adapted Leica cameras.
Type 3 adapters are the latest and most versatile of LTM-to-M adapters.They were invented by Rayqual and, so far as I know, they’re the sole manufacturer. Type 3 identifiers are: 1) The Rayqual or Kendai label (another marketed Japanese brand name), 2) Indents for the Leica 6-bit code on the back that conveys lens identification and characteristics to optimize lens performance with digital M cameras, 3) cutouts on 35 and 50 adapters for Leitz infinity locks. So, Type 3 adds to Type 2 by providing infinity lock cutouts. Overall ,Type 3 adapters are the most versatile with the most features.
The 3 Types of M adapter:. Rayqual M Adapters are still available new in chrome or black finish to match your Leica M. Type III (right) is the most versatile
High Noon Mystery: One of the most asked questions by LTM to M adapter newbies is “Why isn’t my lens infinity mark at the 12 o’clock position? Even more mysterious is that the infinity mark position may move from adapter to adapter, even from camera to camera! Holy Bat Man Barnack! What is going on here? Shush….it’s a secret. Different adapters and different camera makers indeed may have different specs, but there’s more to it than that. When Hugo was designing his adapter, he realized that some lenses (not all) had depth of field scale visible in the M3’s rather large easy to see viewfinder. If the infinity mark was at the noon position, the depth of field scale was difficult to see in the viewfinder. But if Hugo rotated the lens a bit towards the rewind knob, looking at that depth of field scale became easier to see in the M3’s viewfinder!
Which brand M adapter to choose? If you’re a Leica fanatic who insists that everything in your kit be pure Leitz/Leica you’ll have to go with vintage Leica adapters, and they can be pricey, especially if they’re NOS, Mint, and boxed (which is to say, collectible). With generic Chinese adapters, it’s a crapshoot—you can get lucky or maybe not. Voigtlander adapters are very well made but they’re no longer available brand new, and while FotodioX turns out some good cheap adapters for mirrorless cameras, reviews of their Leica LTM-to-M adapter are mixed at best. The best new ones I encountered were Rayqual. They’re made in Japan, fabricated of brass, feature high quality machining, and are available in both chrome and a cool black enamel finish that may show brass in time. Since neither Leica nor Voigtlander ever made Type 3 adapters, the Rayqual Type 3 adapters are also the most versatile. Add a screw mount adapter and 99.9% of the time they’ll fit and function with M-mount cameras including the various digital Leica M's, Epson RD1, Konica RF, Minolta CL and CLE, Leica CL, Zeiss ZM and Cosina/Voigtlander rangefinder cameras including the R2, R2M, R2A, R3M, R3A, R4M, and R4A.
In the exclusive world of interchangeable lens rangefinder aficionados, no other lens mount comes close to equaling the versatility of the humble Leica screw mount introduced over 90 years ago. And thanks to the simple, unassuming, and elegant LTM-to-M-mount adapter you can achieve rangefinder focusing accuracy and TTL metering even on digital M cameras that were well beyond Oskar Barnack’s wildest dreams.
A tip of the lens cap to James Lager, Leica historian extraordinaire, for generously providing most of the the illustrations used in this article
The Curious Ins & Outs of Leica Screw-to-M-Mount Adapters
By Jason Schneider
The Leitz screw-to-M-bayonet adapter, introduced at the time of the Leica M3’s official debut in 1954, lets you mount virtually any Leica screw mount (LTM) lens on a Leica M body, retaining full functionality and precise rangefinder coupling. Elemental and ingenious, the M-mount adapter is a stunning example of non-obsolescence that demonstrated Leica’s commitment to its loyal customers who had purchased thousands of screw mount Leicas and LTM lenses as far back as 1930. The adapter certainly contributed to the success of the Leica M series and even allowed Leica to evolve the Barnack Leica, culminating in the magnificent Leica IIIg of 1957-1960.
Willi Stein, "Father of the Leica M3" left, and Hugo Wehrenfennig, designer of the M-mount system, right.
The man who devised the simple but sophisticated Leica screw-to-M-mount adapter was Hugo Wehrenfennig, the same brilliant mechanical engineer at E. Leitz, Wetzlar who designed the iconic 4-lobed bayonet M-mount. It was his idea to reduce the flange focal distance (FFD) of the Leica M system to 27.8mm, 1mm shorter than the 28.8mm distance from the lens flange to the film plane in previous (screw mount) Leicas. This small difference made it possible to use screw mount lenses on Leica M cameras by means of thin bayonet adapters with an effective “extension factor” of 1mm while maintaining infinity focus and without compromising the optical or mechanical performance of the lens.
Often taken for granted, the screw mount to M adapters were an essential part of the Leica rangefinder system. Allowing backward lens compatibility to the first standard mount screw mount lenses in 1930, these ingenious adapters kidnapped hundreds of thousands of Leica Barnack owners into the Leica M camera club as they screamed in protest over the “outlandlishly huge and heavy” (to them) M3 camera body. Without Barnack owners’ eventual support of the M system, there’s little doubt that the M camera series would have been much less commercially successful. The Leitz screw mount to M adapter was also an important first in 35mm rangefinder camera history. It was probably the first time a new rangefinder mount was made backwardly compatible with older lenses of a different mount. Hugo deserves his own statue beside Oskar Barnack and Hektor, Max Berek’s dog.
Page 86 on M-mount Adapters from James Lager's authoritative Volume III on Leica Accessories, in his monumental series An Illustrated History of Leica.
Copy of James Lager's Leica Viewfinder article on M rear lens caps with "feet" for removing stuck M adapters. Feature was later dropped.
The first three M adapters were Leica code named IRZOO (50mm), ISBOO (90mm) and ISOOZ (135mm), corresponding to the 3 frame lines in the Leica M3. They are auto-indexing, meaning they keyin the proper viewfinder frame line for their marked focal length when the adapted lens is mounted on the camera. The earliest Leitz adapters were engraved with the serial number of the lens it was matched to, and a “job number” on the back to link it to the original order, but both systems were phased outby the late 1950s. Many original Leitz rear M caps have 3 tiny tabs or feet on the back that fit into the notches on M adapters, allowing the cap to be used as a tool to remove an adapter if it gets jammed in the M mount. Evidently this wasn’t a common enough problem, so this feature was later dropped.
Types of screw mount to M adapters from James Lager's iconic Illustrated History of Leica, Volume III, page 87.
Originally, all Leica M adapters, whether made by Leitz or by third parties such as Novoflex, Kilfitt, and Komura, were marked with a single focal length, 28, 35, 50, 75, 90 or135mm. But since the advent of the M6 in 1984 (which displayed 28mm & 90mm, 35mm & 135mm and 50mm & 75mm frame lines in pairs) newer adapters now have dual focal length designations. To ensure backward and forward compatibility, all later Leica M models usethe same system used on the original adapters, so if you have an M adapter made in 1954 it will still work perfectly on a 2022 MP. The only difference is that the 50mm adapter also brings up 75mm frame line, the 90mm adapter also brings up 28mm frame line.and 135mm also displays the 35mm frame line, even though none of these secondary frame lines were available on the M3. Brilliant! Result: with only 3 vintage or modern LTM-to-M adapters you’re golden. And if you’re shooting with an M-mount Voigtlander, which has manually selected viewfinder frame lines, all you need is a single M adapterof any type (Voigtlander made them)—so long as you don’t mind switching it among your screw mount Leica lenses.
Leica stopped making LTM-to-M adapters decades ago but they’re still readily available from independent companies including FotodioX, Metabones, Rayqual and several unnamed Chinese companies, Since they’re essentially a one-time forever purchase I’d go for quality. Generally, the less you pay the more likely you are to waste your time on out of focus pics.
Leitz, New York Product Directory of 1954 listing the new Leica M3 and its many accessories, including M adapters.
Listing for first 3 Leitz screw-to-M-mount adapters in 1954 Leitz, New York Catalog--not bad at $10.50 apiece!
Essentially LTM-to-M adapters come in 3 types, informally designated as Type 1, Type 2, and Type 3.
Type 1 refers to the various pre M8 adapters without indents for digital M lens bar coding, whether made by Leica or any 3[SUP]rd[/SUP] party manufacturer. The key identifier is no indents on the back of the adapter for adding lens bar coding. Please note that Leica’s lens bar coding is patented and apparently not licensed to other lens or camera makers. Therefore, Leica’s M bar coding is only readable on digital M cameras or other adapted Leica digital cameras. Type 1 adapters for 35mm or 50mm lenses are thinner at the bottom, the cutaway providing clearance for the push-in, spring-loaded infinity catch on the focusing tabs found on the following Leica lenses: 35mm f/3.5 Elmar, 35mm f/3.5 Summaron, 50mm f/3.5 and f/2.8 Elmar, and the collapsible 50mm f/2 Summar, Summitar, and Summicron. Type 1 adapters are perfectly usable for film M mount cameras of any manufacture, only being limited for digital M cameras.
Type 2 adapter key identifier is the indents on the back of the adapters for adding bar coding, but they do not have the thin area or cutout at the bottom to accommodate infinity catch lenses. How do you add bar coding? Very Carefully! Various coding kits are available on eBay to make the job easier. Black enamel model paint seems to be the preferable painting medium. Again, take note: bar coding is useful only on digital M and other adapted Leica cameras.
Type 3 adapters are the latest and most versatile of LTM-to-M adapters.They were invented by Rayqual and, so far as I know, they’re the sole manufacturer. Type 3 identifiers are: 1) The Rayqual or Kendai label (another marketed Japanese brand name), 2) Indents for the Leica 6-bit code on the back that conveys lens identification and characteristics to optimize lens performance with digital M cameras, 3) cutouts on 35 and 50 adapters for Leitz infinity locks. So, Type 3 adds to Type 2 by providing infinity lock cutouts. Overall ,Type 3 adapters are the most versatile with the most features.
The 3 Types of M adapter:. Rayqual M Adapters are still available new in chrome or black finish to match your Leica M. Type III (right) is the most versatile
High Noon Mystery: One of the most asked questions by LTM to M adapter newbies is “Why isn’t my lens infinity mark at the 12 o’clock position? Even more mysterious is that the infinity mark position may move from adapter to adapter, even from camera to camera! Holy Bat Man Barnack! What is going on here? Shush….it’s a secret. Different adapters and different camera makers indeed may have different specs, but there’s more to it than that. When Hugo was designing his adapter, he realized that some lenses (not all) had depth of field scale visible in the M3’s rather large easy to see viewfinder. If the infinity mark was at the noon position, the depth of field scale was difficult to see in the viewfinder. But if Hugo rotated the lens a bit towards the rewind knob, looking at that depth of field scale became easier to see in the M3’s viewfinder!
Which brand M adapter to choose? If you’re a Leica fanatic who insists that everything in your kit be pure Leitz/Leica you’ll have to go with vintage Leica adapters, and they can be pricey, especially if they’re NOS, Mint, and boxed (which is to say, collectible). With generic Chinese adapters, it’s a crapshoot—you can get lucky or maybe not. Voigtlander adapters are very well made but they’re no longer available brand new, and while FotodioX turns out some good cheap adapters for mirrorless cameras, reviews of their Leica LTM-to-M adapter are mixed at best. The best new ones I encountered were Rayqual. They’re made in Japan, fabricated of brass, feature high quality machining, and are available in both chrome and a cool black enamel finish that may show brass in time. Since neither Leica nor Voigtlander ever made Type 3 adapters, the Rayqual Type 3 adapters are also the most versatile. Add a screw mount adapter and 99.9% of the time they’ll fit and function with M-mount cameras including the various digital Leica M's, Epson RD1, Konica RF, Minolta CL and CLE, Leica CL, Zeiss ZM and Cosina/Voigtlander rangefinder cameras including the R2, R2M, R2A, R3M, R3A, R4M, and R4A.
In the exclusive world of interchangeable lens rangefinder aficionados, no other lens mount comes close to equaling the versatility of the humble Leica screw mount introduced over 90 years ago. And thanks to the simple, unassuming, and elegant LTM-to-M-mount adapter you can achieve rangefinder focusing accuracy and TTL metering even on digital M cameras that were well beyond Oskar Barnack’s wildest dreams.
A tip of the lens cap to James Lager, Leica historian extraordinaire, for generously providing most of the the illustrations used in this article
