M42 lens mount is an outdated screw thread mount with thread diameter of 42 mm and thread pitch 1 mm for attaching lenses to 35 mm SLR cameras. Was widely used by German and Japanese manufacturers of photographic equipment in 1960-1970s and was perhaps the most popular lens mount in the world. M42 lenses are still produced by numerous manufacturers including Cosina (the famous maker of modern Voigtlander and ZEISS lenses). New or used M42 lenses are available everywhere, they can be purchased both at global and local auctions. In terms of price/quality such lenses are often much better than modern autofocus models. In addition, they are easy to use and will last for a long time due to the high build quality. Perhaps the only significant «drawback» of such lenses is that focusing and aperture control are carried out manually.
In general, shooting with the manual focus lenses is a precious experience itself as you will quickly learn not to rely on camera automation and thereby gain understanding and learn how to control the process of shooting. On the other hand, the lack of automation makes manual focus lenses less suitable for shooting fast-moving subjects.
It should be noted that literally thousands of M42 lenses were produced by various manufacturers, so there can be both successful and unsuccessful options among them. Some models are certainly junk while others are able to compete on par with modern optics. The price of a M42 lens does not correlate directly with its quality because rarity and particular brand name influence on the price much stronger.
You have to use an adapter with your M42 lens in order to be able to shoot with modern digital camera. It is a metal ring with specific mount on the one side and M42x1 thread on the another side. First you attach the adapter to the lens and then attach them on your camera as any of your autofocus lens. Since the adapter usually has no optical elements, the image quality will not suffer and the field of view of the lens will remain unchanged — it will operate the same way as it was mounted on a film SLR camera (except for the auto aperture control which was supported by some models).
In case when the adapter has no focus confirmation chip your camera may refuse to take photos because it will not «see» any lens. This is not surprising — after all, the adapter is just a piece of metal and the camera can not communicate with it. Therefore do not forget to enable so-called «shooting without lens» option in the camera menu when using the adapter without chip.
Shutter speed and ISO can be selected from the camera, as usual, but the aperture control is carried out manually using the corresponding ring on the lens housing coupled with the mechanism for adjusting the lens opening. If the lens has manual/automatic aperture mode switch, make sure that you have selected manual mode otherwise the aperture will be always fully open regardless the selected value.
Focusing is also performed manually. The focus confirmation in the optical viewfinder (no matter, by the means of your camera or a chip on the adapter) usually will not guarantee the precise focusing — it is wiser to rely on your eyes and Live View mode with magnification. The most accurate exposure metering in Aperture priority mode can be obtained with center-weighted and spot metering.
The most convenient usage of M42 lenses is provided with Pentax SLR cameras. Both Pentax K lenses and M42 lenses have the same flange focal distance of 45.5 mm. The automatic exposure metering and focus confirmation in the viewfinder will be available. So all you will need is just M42 — Pentax K adapter without chip. The sensor-shift image stabilization technology will work correctly if you have selected the focal length of your lens in the camera menu.
The flange focal distance is 44 mm for Canon EF mount and 44.5 mm for Sony A mount. This is less than M42 flange focal distance, but fortunately will not create any problems. Automatic exposure metering will work with Canon and Sony cameras however there will be no focus confirmation in the optical viewfinder. Anyway M42 — Canon EF and M42 — Sony A adapters with focus confirmation chip are available and will solve this problem. It should be noted, however, that newer Sony cameras block the shutter in Aperture priority mode if the attached lens has no electronic contacts. In such case it is necessary to use the adapter with chip or shoot only in Manual exposure mode (which is, honestly, not so convenient as you may want). The sensor-shift image stabilization technology will work correctly if you use an adapter with chip coded to the same (or at least similar) focal length.
While focusing near infinity, the rear element of some M42 lenses extends a few millimeters outside the adapter and blocks the main mirror of Canon EOS 5D, 5D mark II, 5D mark III cameras after the shutter release. Fortunately it happens only with specific lenses with focal lengths of 55 mm or greater (one of the lists of such lenses can be found here). As for the telephoto lenses, there’s nothing to worry about starting from the focal length of 100 mm (the only exception is Isco-Gottingen Tele-Westanar 3.5/135mm).
The worst situation is in the case of Nikon SLR cameras. The flange focal distance of Nikon F mount is 46.5 mm which is greater than the M42 flange focal distance and creates problems with focusing at infinity. If you use a simple adapter, the focusing at infinity will not be available at all which substantially narrows the scope of the lens. When using the M42 — Nikon F adapter with lens the focus confirmation in the viewfinder will function inaccurately and provide back- or front-focus and the image quality will suffer (especially at the edges of the frame). To solve the problem, you can install the focusing screen with microprisms. In any case, the focus confirmation in the viewfinder will work regardless of the presence or absence of chip on the adapter. As for the exposure metering, it will be only available with professional Nikon cameras and won’t work with Nikon D3xxx-D5xxx series cameras (you must use an adapter with chip to obtain the focus confirmation).
If we talk about mirrorless cameras, thanks to a small flange focal distance of lens mounts of these cameras the usage of M42 lenses is straightforward — you just need to purchase the appropriate adapter which will physically compensate for the difference in flange focal distances. Exposure metering and focusing at infinity will be available with any mirrorless camera (except for Nikon 1, which does not perform metering in this case), but there will be no focus confirmation when using the adapter without chip. Sensor-shift image stabilization is available with Olympus Micro 4/3 cameras, however, you must «inform» the camera about the focal length of your lens in order for the stabilizer technology to work properly. A significant drawback of using a M42 lens with Micro 4/3 cameras is that «thanks» to the crop factor of the sensor the effective focal length of the lens will increase exactly 2 times, so, for example, the normal prime with focal length of 50 mm and speed of 1.4 will «turn» into the portrait prime 100mm F/1.4. The situation is worse with Nikon 1 and Pentax Q cameras — the effective focal length of the lens will shift significantly to the telephoto range and the lens will completely change its original purpose because of the greater crop factor of these cameras. The only pleasant exception are the Sony A7/A7R full-frame mirrorless cameras with crop-factor 1.
Sony SLT cameras and majority of latest models of mirrorless cameras are equipped with Focus Peaking function which greatly facilitates manual focusing — the camera will automatically highlight with a false-color halo the areas of the image with the highest contrast. All you have to do is just rotate the manual focusing ring on the lens until the halo appears around the object (or its part) you want to be in focus. This method allows for very precise manual focusing on stationary subjects.
Summary table of usage of M42 lenses with digital cameras
|System||Pentax K||Canon EF, EF-S||Minolta/Sony A||Nikon F|
|Flange focal distance, mm||45.5||44||44.5||46.5|
|Exposure metering||Yes||Yes||Yes||Yes (with professional cameras or with adapter which has focus confirmation chip)|
|No (with consumer cameras when using the adapter which has no focus confirmation chip)|
|Focus confirmation in the viewfinder||Yes||No||No||Yes|
|Sensor-shift image stabilization||Yes||No||No (with the adapter which has no focus confirmation chip)||No|
|Type of adapter||M42 — Pentax K||M42 — Canon EF||M42 — Sony A||M42 — Nikon F|
|Lens in adapter||No||No||No||No (= no focusing at infinity)|
|Yes (= image quality will suffer)|
|System||Canon EF-M||Sony NEX||Fujifilm X||Sigma SA|
|Flange focal distance, mm||18||18||17.7||44|
|Focus confirmation in the viewfinder||No||No||No||Yes|
|Sensor-shift image stabilization||No||No||No||No|
|Type of adapter||M42 — Canon EF-M||M42 — Sony NEX||M42 — Fuji X||M42 — Sigma SA|
|Lens in adapter||No||No||No||No|
Photos of adapters