Lens mount
M42 mount
M42 is a 42mm x 1mm screw thread with a 45.46mm register, introduced in 1949 on the Contax S and later adopted by Praktica, Asahi Pentax, Fujica, Zenit, Yashica, and Chinon.
- Type
- screw thread
- Flange distance
- 45.46 mm
- Introduced
- 1949, Zeiss Ikon Contax S (Dresden)
- Status
- Mainstream makers moved to bayonets between 1975 and the early 1980s; Zenit kept building M42 bodies into the 2000s. Still the most common vintage mount on the used market.
About the M42 mount
M42 is a 42mm diameter, 1mm pitch screw-thread lens mount with a 45.46mm flange distance. It appeared in 1949 on the Zeiss Ikon Contax S in Dresden, spread through the East German Praktica line, and became the de facto universal SLR mount after Asahi Pentax adopted it in 1957. Pentax called it the Pentax screw mount, Praktica called it the Praktica thread mount, and dealers still list it as the universal screw mount. Manufacturers on M42 included Asahi Pentax (Takumar), Carl Zeiss Jena, Meyer-Optik Gorlitz and Pentacon, KMZ and other Soviet plants (Helios, Jupiter, Mir, Industar), Fujica, Yashica, Mamiya, Chinon, Ricoh, Cosina, and Zenit.
Because a thread has no fixed rotational index, the aperture scale of an M42 lens can land anywhere around the barrel on a given body or adapter. Aperture operation differs by era: 1950s lenses are usually preset (a click ring sets the value and a second ring closes the blades), 1960s and later lenses usually have an automatic diaphragm with a rear pin, and some late open-aperture metering variants (Pentax SMC Takumar with the ES coupling, Fujica ST, Mamiya SX, Olympus FTL) add extra tabs or pins that need a flangeless adapter for clearance. Most makers replaced the thread with bayonets between 1975 (Pentax K) and the early 1980s; Zenit kept building M42 SLRs into the 2000s.
Aperture control
Three aperture systems exist: preset (two rings, no pin), manual, and automatic diaphragm with a rear pin that the camera body pushes to stop down.
Adapting it
Plain threaded adapter, no optics. Lenses with an auto-diaphragm pin need either an Auto/Manual switch on the lens or an adapter with an inner flange that holds the pin in. Preset lenses such as the Helios 44-2 have no pin and work on any adapter.
M42 lenses in the catalog
| Lens | Focal length | Aperture | Years | Used value |
|---|---|---|---|---|
| Asahi Pentax Super-Multi-Coated Takumar 50mm f/1.4 | 50mm | f/1.4 | 1971-1975 | $70 to $240 |
| Asahi Pentax Super-Takumar 50mm f/1.4 | 50mm | f/1.4 | 1964-1971 | $80 to $400 |
| Asahi Pentax Super-Takumar 55mm f/1.8 | 55mm | f/1.8 | 1958-1971 | $35 to $130 |
| Carl Zeiss Jena Biotar 58mm f/2 | 58mm | f/2 | 1936-1960 | $120 to $550 |
| Carl Zeiss Jena Flektogon 20mm f/4 | 20mm | f/4 | 1960s-1980s | $250 to $750 |
| Carl Zeiss Jena Flektogon 35mm f/2.4 | 35mm | f/2.4 | 1975-1990 | $130 to $380 |
| Carl Zeiss Jena Pancolar 50mm f/1.8 | 50mm | f/1.8 | 1965-1980 | $70 to $260 |
| Fujinon 55mm f/1.8 EBC | 55mm | f/1.8 | 1972-1978 | $50 to $170 |
| Helios 40-2 85mm f/1.5 | 85mm | f/1.5 | 1970s-present | $90 to $350 |
| Helios 44-2 58mm f/2 | 58mm | f/2 | 1958-1992 | $25 to $130 |
| KMZ Industar-61 L/Z 50mm f/2.8 | 50mm | f/2.8 | 1970s-1990s | $25 to $100 |
| KMZ Jupiter-9 85mm f/2 | 85mm | f/2 | 1950s-1980s | $90 to $320 |
| KMZ Mir-1 37mm f/2.8 | 37mm | f/2.8 | 1954-1980s | $40 to $160 |
| Meyer-Optik Gorlitz Trioplan 100mm f/2.8 | 100mm | f/2.8 | 1950s-1970s | $250 to $900 |
| Pentacon auto 50mm f/1.8 | 50mm | f/1.8 | 1960s-1990 | $20 to $90 |
Adapting M42 to a modern body
Frequently asked
Can M42 lenses be adapted to mirrorless cameras?
Yes. M42 has a 45.46mm register, longer than any mirrorless mount, so a plain mechanical adapter reaches infinity on Sony E, Fuji X, MFT, Canon RF, Nikon Z, and L-mount. Plain threaded adapter, no optics. Lenses with an auto-diaphragm pin need either an Auto/Manual switch on the lens or an adapter with an inner flange that holds the pin in. Preset lenses such as the Helios 44-2 have no pin and work on any adapter.
What is the flange distance of the M42 mount?
The M42 flange distance is 45.46mm. It is a screw thread introduced in 1949 on the Zeiss Ikon Contax S (Dresden). Mainstream makers moved to bayonets between 1975 and the early 1980s; Zenit kept building M42 bodies into the 2000s. Still the most common vintage mount on the used market.
How much do M42 lenses cost used?
The 15 M42 lenses in the LensVault catalog range from $20 to $900 used. The least expensive is the Pentacon auto 50mm f/1.8 at a typical $45. Values are estimates from recent sold listings and dealer pricing, not appraisals.