Fernando "El Krusty" Meza 7:44am, 23 October 2008
I've always read about Arkku adapting lenses to the A-mount…

(mod. edit: I hijacked this thread for a long-overdue M42 + lens adaptations FAQ post.)
Arkku PRO Posted 10 years ago. Edited by Arkku (admin) 8 years ago
M42 lenses

The M42 lens mount is an old non-proprietary lens mount, i.e. a means of attaching a lens to a camera. The name of the mount simply means that each M42 lens has 42mm male screw threads (pitch 1mm). The lenses are all-manual, meaning that both focusing and aperture control is manual only.

The M42 mount begun with an East German Zeiss camera slightly after World War II, but it was later popularised around the world by Pentax, which is why it is sometimes called the “Pentax Screw Mount”*. It is probably the most popular lens mount of all time, and dozens of manufacturers have made cameras with this mount (I have film bodies from some 12 different manufacturers myself, and I haven't even tried to collect them all). Lenses were made by an even greater number of manufacturers, and indeed some are still in production (e.g. by the modern Carl Zeiss and some ex-Soviet manufacturers). Old lenses are readily available everywhere, including eBay and any place where used camera gear is sold, and some rival modern lenses in quality (and certainly defeat them in “bang for buck”).

(* Note that Pentax doesn't use the M42 mount anymore on their cameras. However, their DSLR system is still very friendly towards M42 adaptation, allowing in-body stabilisation to work without special electric adapters, etc. See below for how it is with Sony. Most other M42 manufacturers have also made lenses with different mounts, so one should be careful to buy specifically the M42 mount version for adaptation to a DSLR.)

One reason for using M42 lenses on modern cameras (e.g. Sony DSLRs) is that one can try out a great variety of lenses at very affordable prices (e.g. some nice, fast primes cost around $/€ 10-20). Most M42 lenses are primes (i.e. fixed focal length), while modern equivalents are more typically zooms and most modern primes are costly special-purpose lenses for pros. Same goes for fish-eyes and other special lenses. M42 lenses also retain their value very well, so one can always get rid of “extra” lenses, often even for profit. Additionally, old lenses tend to be metal and glass, instead of plastic and, well, plastic, like modern lenses. Many old manual focus lenses are very pleasing to handle, and quality lenses will last a lifetime of use.

Using old all-manual lenses is also a great learning experience, since one quickly learns not to rely on the modern automatics, and thus gains a better understanding and control of one's photography. As a downside, the lack of automation makes these lenses less than suitable for fast-paced action photography.

(Note that since there is probably a greater variety of different lenses available in M42 mount than any other, there are both good and bad ones. Some lenses are outright crap, others rival the performance of the most expensive modern ones. The price of M42 lenses doesn't correlate very well with how good they are; rarity and brand name, as well as fame on sites like flickr, affect the price far more. The best deals and the best lenses are found with patience and diligence, and it is generally better to look for many alternatives simultaneously instead of desperately trying to find a great deal on one specific lens.)

Note that M42 accessories like macro bellows, extension tubes, reversing rings, and adapters from other mounts (like T2, Adaptall-2, M39 or Pentacon Six) to M42 mount also work on M42 adapters. Macro photography in particular is considerably cheaper with M42 lenses than modern autofocus lenses.

M42 lenses on DSLRs

In order to use M42 lenses with a Sony DSLR, an M42 adapter is required. The adapter is basically just a metal ring with a male Sony/Minolta AF mount on one side and a female M42 mount on the other. The adapter screws onto the M42 mount lens and the lens-adapter combination can then be mounted on the Sony DSLR just like any other lens. Since the adapter contains no optical elements, there is no degradation of image quality or change of focal length—optically the behaviour of the lens is the same as it would be on an M42 mount film body.

M42 lenses can be similarly adapted to most other modern DSLR systems as well, with the notable exception of Nikon, with which the adapter requires additional glass elements in order to maintain infinity focus (because of the Nikon mount's greater registration distance). This FAQ/guide focuses on Sony Alpha DSLRs, being the author's system of choice, but many parts are applicable to other systems as well.

If the M42 adapter is not electric (see below for more on electric adapters), the DSLR may refuse to take a picture because it sees no lens attached—after all, the adapter is just a piece of metal, so the camera can't communicate with it. Some Sony DSLRs have a menu option to allow shooting “without a lens”. These include at least the A100, A700, and A850 and A900 with updated firmware (original release firmware does not have this option on A850/A900). On all of these four cameras the option is on the second page of the custom menu (gear icon). On the A100 the option is the second of two “Shutter lock” options and should be set to “Off: no lens”. On A700, A850, and A900 the option is “Release w/oLens” and should be set to “Enable”. Once this lock is disabled, these cameras can shoot in both A and M modes with manual lenses. On cameras without this option, only M-mode works (shutter lock is disabled automatically in that mode if the menu option is not available—if you find that you are unable to shoot in M mode with a manual lens, your camera should have the menu option).

In actual use, the shutter speed and ISO sensitivity are controlled on the camera as usual, but the aperture control is on the lens. (See below for details about aperture control.) Focusing is done manually. (See below about focusing.) When shooting in manual exposure mode (M), the reading from the camera's light meter is still available; there's an EV scale in the viewfinder (-2 . . -1 . . 0 . . 1 . . 2) under which a little bar moves to show the exposure. When this bar is under the zero (0) position, the exposure is “correct” according to the camera's meter. In aperture priority mode (A) the camera automatically sets this value when the shutter release is pressed. In my personal experience, the most accurate exposure with manual focus lenses is obtained in centre-weighted and spot metering modes. One may apply exposure compensation to correct any consistent errors in exposure.

Note that unlike automatic lenses, adapted M42 lenses must be set to the shooting aperture before the meter reading is applicable, but of course it is also possible to compensate manually, e.g. if the meter reading is +1 EV with the lens wide open, one can close the aperture by one stop.

Other manual focus lenses on the Sony Alpha system

Note that other kinds of manual focus lenses, for example Minolta MC/MD lenses (e.g. any Minolta lens with the name “Rokkor”) are not M42 mount lenses, and can not be used with an M42 adapter (the mount is entirely different). Old Minolta MC/MD lenses can not be adapted for proper infinity focus on the Sony/Minolta AF mount with a glassless adapter. This is physically impossible because the lens needs to be closer to the camera than the camera's built-in mount allows (i.e. the Minolta MC mount has a registration distance less than that of the Minolta AF mount)—the adapter would need to have negative thickness.

A glassless Minolta MC/MD to Sony adapter is several millimeters thick to accommodate the bayonet mount of Minolta MC/MD lenses, and therefore acts like a macro extension tube. In practice this means that only close-focusing photography is possible with such an adapter, e.g. a 50mm Minolta MC lens mounted on such an adapter on a Sony DSLR will only be able to focus to a 30 to 60 cm (1' to 2') distance at most. Longer lenses can focus a bit farther, shorter lenses not even that far.

There are also Minolta MC/MD adapters with additional glass (or plastic) elements which correct for the focusing distance. Despite claims of some sellers, these additional elements will always change the focal length somewhat (typically by a factor of 1.2× or thereabouts). The additional glass may also cause flare, loss of contrast and sharpness, or similar issues, though in optimal conditions these issues will generally be quite minor with most lenses. It has been reported that the best quality adapter is an old Minolta-made one with a 2× teleconverter built-in, but of course that adapter doubles the focal length of the attached lens. Remember that any change of the focal length with these adapters results in a smaller relative aperture, e.g. an f/1.4 lens mounted on the usual type of adapter with 1.2× teleconversion factor would actually be closer to f/1.7. This is because the focal length increases but the absolute (physical) size of the aperture remains the same, therefore causing the aperture relative to the focal length—which is what the f/-notation means—to change. See here for a comparison of two adapters versus the same lens without an adapter.

Due to these limitations I don't personally recommend buying “new” Minolta MC/MD lenses for use with Sony DSLRs—it's almost always better to get similar lenses in e.g. M42 mount. People who already have important lenses in Minolta MC/MD mount can certainly benefit from an adapter, however. (Note that Minolta AF lenses work directly without an adapter, and some are highly recommended. Just be sure to check that you are getting an AF-mount lens! And, once again, these have nothing to do with M42 lenses.)

As a slightly more extreme solution for using an MC/MD lens on my Sony DSLR, I have managed to convert this Minolta MC 58mm f/1.2 lens to the Sony/Minolta AF mount. It wasn't very difficult (and I wrote a guide to doing the conversion), but most lenses are not this easy to convert. Spending the time and effort on a lens conversion also makes more sense with exceptional lenses, such as the f/1.2 which has no modern or even direct M42-mount equivalent. In any case, conversion is one alternative for the more dedicated hobbyist, but not a general solution for using MC/MD lenses.

There are also some lens mounts that can be adapted to M42 mount. Most notably these include Tamron Adaptall-2 lenses (which were designed for use on “any camera” by always using an adapter, hence the adapt-all name), and Pentacon 6 mount medium format lenses, which notably include some nice (but large and heavy) telephoto lenses from Carl Zeiss Jena. Other medium format lenses (with large registration distances) may be similarly adapted if a matching adapter is found or made. It is also possible to mount long focal length large format lenses on M42 mount macro bellows with relatively simple DIY adapters. When used with the proper adapter, all lenses that can be adapted to M42 mount can also be used on Sony Alphas just like “real” M42 mount lenses.

For more information on general lens compatibility with Sony Alpha, check out the Sony Alpha lens compatibility FAQ.

Aperture control on M42 lenses, auto/manual aperture

A thing to note about M42 lenses is that there are two fundamentally different “modes” to control their aperture: automatically and manually. Automatic control means that the lens remains wide open even when the user changes the aperture setting; much like today's AF lenses, but with M42 lenses the setting is changed by turning a ring on the lens instead of a dial on the camera. In auto-aperture mode the lens only stops down to the selected aperture when a pin on the back of the lens is pressed down. The idea is that most M42 film bodies will press this pin down whenever the shutter is released, which allows easy focusing wide open. The problem is that cameras on which M42 lenses require an adapter, such as Sony Alphas, do not support this mechanism and are therefore unable to stop down auto-aperture lenses.

A picture illustrating the aperture pin (top left, protruding from near the rear element) and two types of A/M switches (in the middle with the text “auto” and "man.” and on the bottom right with “M”):

M42 Lens Aperture Pin

Because no DSLR has the capability to directly control the aperture of M42 lenses, auto-aperture mode will not work on DSLRs, which means that the aperture control on adapted auto-aperture lenses is rendered completely ineffective. Some means must be devised to press the aperture pin unless the lens is to be used wide open all the time.

Some lenses have an auto/manual (A/M) switch that allows the user to force the lens into manual-aperture mode, which solves the problem by effectively making the lens a manual-aperture lens (although maintaining auto-aperture capability on film bodies). Other lenses only have manual mode to begin with and are directly usable. Problematic lenses are those that have auto-mode only. For these problematic lenses there are some adapters with an additional metal “lip” which presses down the aperture pin (all the time). These adapters solve the issue for auto-aperture-only lenses, but aren't compatible with all lenses because some won't physically fit in all the way due to the lip. A more selective solution is to jam down the aperture pin on the problematic lens itself.

A reliable (and reversible) solution to pressing down the aperture pin on the lens is to open up the rear of the lens and jam down the pin from within. My favourite trick is to cut a piece of hollow plastic from a cotton swab (aka q-tip) and insert this tube over the pin inside the lens, thus preventing it from moving upwards. See this picture for an example of such a modification. It is easy to do on most lenses and requires no tools other than a screwdriver (for opening the lens) and scissors (for cutting the cotton swab).

(Other solutions include gluing the pin down, or simply forcibly pressing it into the lens until the auto-aperture mechanism breaks, hopefully leaving it in manual aperture mode. I don't recommend these crude, and usually permanent, solutions.)

Some manual-aperture M42 lenses have two separate rings controlling the aperture. These may be a bit confusing at first, but actually they are perhaps the most convenient way of controlling the aperture manually. The way a two-ring system works is that one ring actually stops down the aperture, while the other ring limits the range over which the other ring can be turned. The idea is to use the limiting ring (which does not stop down the lens) to choose the shooting aperture, focus with the lens wide open, and then turn the other ring (which does stop down the lens) until it hits the limit set by the other ring. This way one can toggle between wide open and the aperture pre-set by the limiting ring, without having to look. The stopping-down ring is also generally stepless in motion, so aperture can easily be set to any intermediate value (e.g. to precisely match the meter reading). These lenses have what is called “pre-set aperture control”, because the limiting ring is used to “pre-set” the shooting aperture. (Some pre-set lenses, such as the Volna-9, do the same thing with only one ring; lifting the ring up allows it to be dropped into a slot to set the limit, and turning the ring normally stops down the aperture.)

(Tip: The Auto/Manual switch present on some lenses can also be used to quickly stop down to the selected aperture, effectively simulating the behaviour of a pre-set lens. One can pre-select the aperture with the switch in auto position, focus wide open, and then flick the A/M switch to stop down the lens without having to look at the lens or count the clicks on the aperture ring. This takes some getting used to, but can be very convenient with certain lenses.)

Lenses with auto aperture, as well as some manual-aperture lenses, generally have only one ring to control the aperture. Usually this ring has click-stops for each full stop of aperture, and possibly for half-stops as well. I have never encountered an M42 lens with clicks for one-third stops, which means that to better match the shutter control on the camera it is beneficial to set the camera to operate at one-half stop increments instead of the default one-third stop increments. This way each click on the shutter speed dial on the camera matches one click on the aperture ring, assuming half-stop increments. With one-third stop increments one can only match full stops with three clicks of the shutter speed dial. (Not all Sony Alphas have the capability to use half-stop increments, however, but e.g. the A850 and A900 do.)

Electric M42 adapters for SteadyShot and AF confirm

People getting started with M42 lenses should probably just get a reasonably cheap adapter to begin with. Once they have decided which M42 lenses they will be using most, they can upgrade to an electric adapter programmed for the specific focal lengths of their lenses. This is required for proper SteadyShot operation because the in-camera anti-shake needs to know the approximate focal length to properly compensate for shake—short focal lengths require less compensation than long focal lengths. But before assuming that an electric adapter is absolutely necessary one should remember that most cameras—including all film cameras, and all Canon and Nikon DSLRs—have no in-body stabilisation to begin with, so it is entirely possible to live without it. (And indeed, SteadyShot may still help a little even without the electric adapter.)

The use of an electric adapter also enables the focus confirmation dot, which lights up in the viewfinder when the camera's autofocus system determines that the (manually focused) subject is in focus. (You can observe how this works by using an autofocus lens in manual focus mode.) This AF confirm infrormation may not be super-accurate, and therefore can't usually be relied on to focus for you with fast primes wide open, but it does speed up focusing by narrowing down the focusing range.

An additional benefit of electric adapters is that they enable the use of the “A” mode (aperture priority exposure) on the camera models that normally don't normally support it with manual focus lenses. Without an electric adapter such cameras are limited to “M” mode.

James Lao on dyxum.com makes custom-programmed electric M42 adapters, while others (e.g. on eBay) sell ones programmed for “typical” focal lengths (if the listing doesn't say which focal length is programmed into the adapter, it is almost certainly 50mm). There are also multi-data adapters with several selectable focal length settings in a single adapter (e.g. James Lao makes one with up to four settings per adapter, and others sell “standard” 50/85/135/200mm adapters). The way these multi-data adapters work is that one attaches the adapter with the camera powered down, then powers up with the shutter release half-pressed if the focal length is to be changed. During the first 10 or so seconds after power-up, the settings can now be cycled by repeatedly half-pressing the shutter release. The selected setting can be observed by looking at the changing maximum aperture value (each focal length setting has a different maximum aperture)—one may need to simultaneously turn the aperture-setting dial to see what the widest aperture is. (Eye-start AF can interfere with this process, so one should either disable it or use the LCD display for checking the setting.)

Important: When using an electric M42 adapter, the aperture setting becomes adjustable on the camera, but it doesn't work because the camera can't control the aperture of M42 lenses. However, the camera thinks that it can control the aperture, which is why the aperture setting on the camera must always be set to the widest aperture (smallest f-number), regardless of whether or not it matches the maximum aperture or the shooting aperture on the lens. That is, if your adapter is programmed to present itself as a 50mm f/1.7, lens you must always set the aperture on the camera to f/1.7—no matter what lens or aperture you are using!

(The reason for this is that the camera always meters wide open and only stops down when the picture is taken, so it believes that the amount of light it is seeing is always with the lens wide open. If an aperture other than “wide open” is selected, the camera compensates for the anticipated stopping down, causing overexposure when the lens—unbeknownst to the camera—doesn't stop down on the camera's command. The aperture actuator may also hit the lens and cause a camera error that can only by recovered by cycling power, possibly by removing the battery… So, always select the widest aperture on the camera—with M42 lenses it has nothing to do with the aperture you select on the lens!)

Infinity focus issues with M42 adapters

Any working(!) M42 to Sony/Minolta AF adapter is capable of getting any working(!) M42 lens close enough to the sensor, thus allowing infinity focus with no modifications to the lens or the adapter, and without any extra optical elements. This means that M42 lenses can be used on Sony Alpha DSLRs with no degradation of image quality or loss of focusing capability.

However, in my experience, many M42 adapters are (despite seller's claims to the contrary) slightly too thick, and therefore may require sanding down (of the adapter) to reach critical focus at infinity. Note that these differences are very small, and it is very easy to just blame the lens for lack of performance instead of suspecting the adapter (through the viewfinder it will often appear to work perfectly). Here's an old comparison of mine, showing this difference between two different M42 adapters.

Note that there's not necessarily any strong correlation between price and accuracy of an adapter, nor can any specific brand of adapter be considered without fault (even if some specimens of that brand are). It probably comes down to manufacturing tolerances of different components adding up. However, so far none of the electric adapters I've tried (e.g. those made by James Lao, which I recommend) have exhibited problems with infinity focus.

In any case, if a lens seems to have poor performance at infinity despite working fine at close-up distances, the adapter may be at fault. A bit of sanding with fine-grade silicon carbide paper should do the trick; place the wetted paper on a flat surface and rub the face of the adapter on it in a figure-eight pattern, reversing direction occasionally. Check infinity focus periodically. It's best to first try with relatively short focal lengths, since they are most affected by a given amount of thickness, and fine-tune later with a longer lens (which has the least depth of field at a given focusing distance). Always check with multiple lenses, because individual lenses may have incorrect focus!

Focusing with manual focus lenses

For most users the biggest hurdle to overcome when using M42 lenses is learning to focus manually. Electric adapters help a little by enabling the focus confirmation dot visible in the viewfinder, but the accuracy of that “AF confirm” is not sufficiently accurate for every use. For accurate manual focusing “by eye”, the first thing to check is that the diopter adjustment of the viewfinder is properly set. Personally I find the best way to set it is to focus the lens very accurately at infinity (e.g. at distant buildings or trees visible from a window), verify focus by taking a picture, and then adjust the diopter setting until those focused objects look their sharpest.

The act of focusing itself should generally be performed with the lens wide open for minimum depth of field, and the aperture stopped down only after focusing. In practice it can sometimes be better to focus slightly stopped down, especially if it's the shooting aperture—for example, if you are using an f/1.4 lens at f/2.8, you could try focusing at f/2 or directly at f/2.8. Some lenses are soft wide open, and this may make focusing more difficult even though in theory it should be the most accurate setting.

Personally I find it helpful to look at highlights (e.g. catchlights in the eyes of a subject) or the surface texture (e.g. hair). Focus to make the highlights as small as possible, or the surface texture as clearly visible as possible. If it doesn't seem possible to tell the exact right position, try to find two “equally out of focus” positions, and focus “in the middle”—this simple trick can be surprisingly effective. Note that with a digital camera you can also bracket focus because the “film” is essentially free—just take many pictures while turning the ring between the two “equally out of focus” positions. (Also try to see if the best focus consistently ends up on one side; it may be that the focusing screen is slightly misaligned, or the diopter adjustment is wrong.)

For serious manual focus users one option is to get a replacement focusing screen. Sony makes an official manual focusing screen (“type M”) at least for the A850 and A900—the same screen works on both models, but not on other current cameras. At first glance the type M screen looks just like the original (“type G”) screen, but it shows depth of field much more accurately. The price to pay for this accuracy is that it darkens very fast, and the manufacturer's recommendation is to use it only with f/2.8 and faster lenses. (Personally I've found it usable even with f/8 lenses in well-lit conditions, but in dimly-lit indoors I'd say f/4 is the smallest reasonably comfortable aperture.) When the type M screen is installed, an option in the camera's settings must be changed to obtain correct metering with this darker screen (see the manual).

There are also various unofficial focusing screens available for Sony Alphas, e.g. on eBay and sites like focusingscreen.com. These screens are often made from modified focusing screens intended for film cameras. The problem with these screens is that they are generally fiddly to install, a bit dim (so they potentially affect metering accuracy), and they may need messing around with shims (usually included) to get them properly aligned. The major benefit, however, is that they have split-prism and/or microprism focusing aids. A split-prism splits the centre of the image in two, and correct focus is obtained by aligning the two halves with one another. Microprisms do the same on a much smaller scale, creating a very distinct “shattered” image when focus is not perfect.

Split-prisms and microprisms are very fast and very convenient for manual focusing, but unfortunately both split-prisms and microprisms depend on the aperture setting and black out completely below a certain aperture limit (typically soon after f/5.6). Unlike the “type M” focusing screen, these focusing aids are not usable at all below the aperture limit. I personally recommend the type of screen with a split-prism in the centre surrounded by a microprism collar, because the split-prism works with slightly smaller apertures than microprisms do, but microprisms are (in my opinion) faster to focus with. Users of fast lenses (only) may also consider a microprism-only screen, but I don't recommend a split-prism-only screen because it depends too much on having some clear “line” to split.

Mirror clearance / Lenses hitting the mirror?

When researching M42 lenses online, one may read warnings about adapted lenses (M42 or otherwise) hitting the mirror on some cameras, Canon full-frames in particular. As far as I know, this is not an issue with Sony Alpha DSLRs—I have tested dozens of M42 lenses on both A100 and A900 cameras, including several lenses that are listed as incompatible in Canon EOS 5D M42 compatibility lists. I have also never heard reports of anyone having issues with mirror clearance using M42 lenses on Sony Alpha DSLRs. Of course, this does not prove that no problematic lens could exist (e.g. some very rare old Yashinon lenses require true mirror lock-up to mount at all, and are thus incompatible with almost every M42 film camera as well)… However, I can confidently say that for an M42 lens to threaten the mirror even on full frame Alphas, it would have to have really obvious protrusions on the rear, extending well beyond the rear of the M42 adapter.

In short: Mirror clearance is not an issue with Sony Alphas.
OHh... ok ok,

First thing first, again, thanks for the fast, precise and wise response as usual. It was long since I read the Rokkor 58 f/1.2 adaptation so I got a little lost in there, and the Vest Pocket Kodak to M42 was pretty illustrative too.

I couldn't agree more on that, testing adapters and get to know the thickness needed for correct focus to infinity and the way to do so by the comparative images is great too. Now I remember why the electric adapter is needed, I read months ago about it (the pre-programmed pins for certain focal lengths) and now everything makes sense.

Thanks again fro shedding some light upon us.
autocara64b 10 years ago
My God Arkku, you have to put together all of those texts you have been writhing all over the place; it seem you could publish a book on the technical aspect, modification of lens and what can and cannot be done in the DSLR world.
Food for toughts
Arkku PRO 10 years ago
I figured it would be easier writing it all here once instead of writing it weekly in various flickrmails. =)
wakeful vest [deleted] 10 years ago
Hello all, this all sounds quite promising. I would like to know if there is any known case of mirror jamming into the back of the lense, like it can happen in some cases on the canon system.
dramatic riddle [deleted] 9 years ago
This is all great information. Thanks for compiling it. I think I am either a slow learner or just afraid I will hurt my camera in some way, so I have a question or 2. I have an Alpha 200 and I have a 500MM mirror lens with an M42 adaptor. I was able to use this on my film camera (HTsi Maxxum). To use this on my Alpha, I think I understand that I need to set the camera on manual focus, and M to control aperture (although lens is fixed F8) and shutter speed. Is there anything else I should set or do? Thanks for your patience. Jack
Arkku PRO 9 years ago
You can never control the aperture of adapted (M42 or other) lenses with the camera, because the aperture control is different. With your A200, I believe the ability to control the aperture will not even show up in M mode when you have an M42 lens attached on a non-electric adapter.

(If you are using an electric adapter, you will see the aperture control but it will not work—you should then just set it to the largest aperture, i.e. smallest number, possible, even if it doesn't match the lens or the aperture you are using. With an electric adapter you can also use the A mode, but the above advice about the aperture control still applies.)

So, you only control the aperture on the lens itself. And in case of the mirror lens, you just don't. It's the shutter speed (and ISO sensitivity) that you should set on the camera (in M mode).

In any case, don't worry too much; just set the camera to manual focus and M mode and put on the adapter + lens and you should be good to go.
wstryder 9 years ago
This was extremely informative and answered every single question I had about using m42 lenses with Minolta/Sony DSLR!

Kiitos Arkku tästä!
Very well done Arkku.

I really like the amount of detail and time you have invested into this topic.
Arkku PRO 9 years ago
Thanks; I mostly update it based on questions I see in this group or in my flickrmail, so everyone do let me know if there's still something left unclear. =)
shodanman 9 years ago
Arkku, thanks for a excellent description!
I would just like to confirm the following with you. If using a chipped adapter programmed to lets say 50/1,7 with a 50/1,4 lens, one should set the camera to 1,7 not 1,4 for correct exposure right? Having the same focal lenght on the chip and lens is crutial for correct SSS correction. But how important is it to have matching f value on the chip (like 1,4 for a 1,4 lens) and why?
Arkku PRO Posted 9 years ago. Edited by Arkku (admin) 9 years ago
shodanman: If the adapter is programmed to present itself as a 50mm f/1.7 lens, you cannot select f/1.4 in the camera because the adapter reports f/1.7 as the maximum. In any case, with such an adapter you should always shoot with the camera set to f/1.7, no matter what lens or aperture you are using.

It's not important to have a matching aperture in the adapter. One possible benefit may be with focus confirm accuracy because it may allow the camera to estimate the depth of field better. Also some cameras have higher precision AF sensors in the centre spot, and these only work with f/2.8 or faster lenses (then again, most of the common M42 lenses are f/2.8 or faster). And I don't know whether or not the camera requires an aperture faster than f/2.8 in the adapter to use these sensors.
shodanman 9 years ago
Kiitos! :-) I'm eagerly awaiting a M42 adapter and a SMC Tak 50/1,4 for my A100...
boyputik 8 years ago
Q: Is there any chance that Mounting an m42 lens can damage the mirror ?
Arkku PRO 8 years ago
boyputik: Already answered at the end of the FAQ post, but in my experience, no. (In theory, of course, there could be a lens that extends too far into the body even for Sony DSLRs, but I doubt such a lens could be used on M42 film cameras without permanent mirror lock-up. Actually, such lenses do exist, but they are easy to spot as they nearly touch the film when mounted.)

M42 mirror clearance is only an issue with certain full frame Canons.
boyputik Posted 8 years ago. Edited by boyputik (member) 8 years ago
Thanks Arkku all that shaving had me worried for a while = )

I bought a second adapter with AF confirm chip it's excellent it 's focusing was perfect out of the box ....
Simon in Southend PRO 8 years ago
Regarding P6 mount...
I've bought a tilt adapter and an Carl Zeiss Jena 80mm f2.8 lens on ebay (yet to recieve it). Is it going to work okay on my a500. Will the tilt effect be pronounced enough? Will the lens manage to focus to infinity?
Arkku PRO 8 years ago
Simon in Southend: The Pentacon 6 mount has a very long register distance and can focus to infinity on every small format SLR. I don't know how much tilting the adapter will allow, but it should have some effect or they probably wouldn't be making those adapters…
Deutero 8 years ago
this topic has been revived :D . Wanted to know if there is a difference between m42 mount and the T2 mount
Arkku PRO 8 years ago
Yes, they are different mounts. =)

(Specifically the thread pitch is different so they are not physically compatible and trying to force one onto the other will probably strip the threads from the T-mount side. And the register distance is different.)

T-mount lenses can, however, be adapted to M42 mount.
Zoemies... 8 years ago
many thanks Arkku!
Canadapt 8 years ago
Thank you for the clearest and most thorough explanation about M42 adaptation that I have come across ... very helpful!
PSDigital 7 years ago
Excellent thread!

Do you recommend any brands over others when it comes to M42 glass?
Fernando "El Krusty" Meza Posted 7 years ago. Edited by Fernando "El Krusty" Meza (member) 7 years ago
There are tons of great lens choices, and I'm sure arkku uses some even beyond the M42 range and adapt them for its use. There are some really hard to find and unique lenses or some brands that have a great line of M42 glass. I can only tell you the bests known and of what I've used that gives great IQ and build.

I know that one of the more sought for is the Pentax SMC (super multi coated) or the Asashi Super Takumar. Both are from pentax, but the Super Takumar are of greater quality. The Super Takumar 50mm 1.4 and the 85mm 1.9 are the best. Specially the 85m since it's so small! I had two copies of the 50mm and sold each for over $100dlls, but you may find them cheaper.

It's like everything. A nice brand will yield good glass. Like Yashinon DS from Yashica, Fujinon or even some Vivitar, I had a vivitar 28mm 2.5 that was really sharp, and I found it on a swap meet.

Edit: There's also Helios and Carl Zeiss glass but that goes pricier over the internet. Still you may find some locally.

Once you get into using M42 glass is always a treasure hunt. And a really fun and rewarding one.
Arkku PRO 7 years ago
psdigital: Well, personally I have a thing for Fujinon lenses, but honestly it's more about collecting them than the brand somehow being the best choice for every focal length. In fact, I would suggest not to get stuck with the idea of a specific lens or brand, because it's a lot easier to find a good deal when you're open to many alternatives. You may also discover hidden gems… =)

(Of course, it's a good idea to look for sample photos, e.g. in the M42 group before buying.)
Calon2011 7 years ago
Thank you Arkku for taking the time to do this, has answered a lot of my questions without me having to ask them lol.
Light Collector PRO Posted 7 years ago. Edited by Light Collector (member) 7 years ago
Wanted to say how pleased I was to find this post. In my "film" life, I used a Pentax Spotmatic and a Pentax ES11. As a result, I have the following lenses:

SMC Takumar 35mm f3.5
SMC Takumar 55mm f1.8
SMC Takumar 200mm f4

These have all been sitting around collecting dust since I went digital, but since selling them would not have produced a great wad of cash, I kept the cameras and lenses for sentimental reasons.

I recently purchased a Sony a55 and started thinking about selecting some lenses. I never gave any thought to trying to adapt the the old Pentax lenses to the Sony until I found someone on Flickr making reference to adapting an SMC lens. That eventually lead me to your post. From what I read here and your FAQs, it would appear that with the purchase of an M42 adapter, I can instantly add three prime lenses to my kit bag at virtually no cost!

Thanks for a very well written article. Another bonus from my Flickr membership!

RienOnVanIsle 7 years ago
Great information, very helpful. However, I can't get infinity with my adapter. No sanding of the front plate of the adapter is going to help, because it is the rear ring of the adapter that causes trouble: the rectangular pin on the M42 mount sits against that ring, which obviously doesn't go back far enough. I would like to try and fix this, but maybe someone has had the same issue and found a good solution.


Arkku PRO Posted 7 years ago. Edited by Arkku (admin) 7 years ago
RienOnVanIsle: Both your adapter and your lens are “non-standard”:

1) The “rear ring” is not a standard feature in M42 adapters (in fact it's quite uncommon; until recently it was difficult to find an adapter with it for M42 to Sony). Its purpose is to press in the aperture pin on auto-aperture M42 lenses (unless modified, they would otherwise be wide open all the time if the lens doesn't have an auto/manual switch).

2) The “rectangular pin” is not a standard feature in M42 lenses. (I would guess that this is a Pentax S-M-C Takumar lens?) It's a manufacturer-specific extension, probably for alignment of some open-aperture metering system (which only works on that manufacturer's select “M42 native” cameras, not via adapter or in other M42 bodies).

Fortunately, in your case you also have (at least) two possible solutions:

1) You can get an adapter without the inner ring; your lens looks like it has an auto/manual switch, so you don't need the ring to press down the pin. Or you can just remove the ring on this adapter, but you may wish to keep it for other lenses. (If I'm mistaken and your lens does not have the switch, you can choose option #2 or you can convert your lens to manual aperture only as described in the FAQ. This modification is usually completely reversible.)

2) You can file away the rectangular pin on the lens; it's not required for any standard functionality, so unless you will be using this lens on the original manufacturer's compatible M42 bodies, its removal should have no effect. (Of course you may wish to preserve the collectible value of the lens and not modify it, in which case solution #1 is better, even if you need to do the manual aperture modification.)
even board [deleted] 7 years ago
wonderful guide, thank you!
RusseII Lees 7 years ago
...wish I had seen this a few months ago! I've been reading loads of different little bits here there and everywhere, and everything I ever needed was in this post! Aaaahhhh
Zekewhipper PRO 7 years ago
I've started to use old M42 primes, and have no regrets about it.
robirobirobi 7 years ago
Very informative thread!
KaneDWilliams 6 years ago
So are there any issues using M42 lenses (with adapter) on SLT cameras, such as my SLT-A65?

Arkku PRO 6 years ago
No known issues. With electric adapters there shouldn't even be any theoretical issues since the camera wouldn't know that it's an adapted lens, but I also assume that the SLT cameras will fire “without a lens” when set to M mode (or have the “release w/o lens” menu option).
KaneDWilliams 6 years ago
I received a nice, well made, strong, but not thick chipped adapter ring for my 135mm Flektogon. However, when I screw it to the lens, it does not screw all the way on so it ends up flush with the lens body. There is a gap of about 1mm.

When I tried to focus on the window of the house about 50m away, I could not focus. I reached infinity on the lens, but the window was still soft. However, I was wide open on the aperture and when I stopped down to f16/f22, it seemed to be in focus.

Is this normal? I think not.

Pedro del zurdo 6 years ago

I have a similar situation with my Helios 58mm f2, the adapter ring tightens up, but doesn't line up the lens in the expected "top dead centre" position. i.e. the lens markers are way off to the side.

If you can try another M42 lens (preferably similar focal length) that will establish whether the thread on the lens for some reason is an issue. Also, you may wish to try out a replacement adapter, in case of a defect, or you can examine the thread and establish where the thread is being prohibited from further rotation. - This is something I have in mind for the Helios+M42 adapter combination, although this does depend on how enthusiastic you are...

LJ Stamford 6 years ago
Hi Kane,

I had the exact same problem with an adapter I bought from eBay. It was an electric adapter of the cheapest possible kind - the electric contacts and chip were glued on fairly carelessly, and I eventually realised that it was excess glue causing the problem by preventing the adapter from fully screwing down. If you have the same problem you might be able to fix it by scraping some glue off with a scalpel, but be careful not to damage the chip (or your fingers obviously!). Alternatively, you'll need a new adapter.

I imagine the reason the building was in focus at f16-22 is just that the depth of field is much greater at that setting than at wider apertures, allowing the lens to focus on subjects that it's not actually focused on, if you see what I mean.
Arkku PRO Posted 6 years ago. Edited by Arkku (admin) 6 years ago
The behaviour described is not normal; the lens should screw in all the way into the adapter. If it does not, the remaining threads act as a very short extension tube, which shortens the maximum focus distance. Stopping down increases depth of field and alleviates the issue, but does not solve it.

Anyhow, please start another thread to discuss specific adapters and/or solutions if needed, I try to keep any lengthy non-FAQ discussions off of this FAQ post. =)
Filip alpha200 6 years ago
@ Arkku
I still have one question about the mirror clearance:
I have lenses with an M/A switch,
If i accidently switch from M to A the pin comes out again.
Is there than a risk that the mirror hits the pin?
Panda.* 6 years ago
I can answer this one... The Pin won't touch the mirror, don't worry
mellowmark Posted 6 years ago. Edited by Arkku (admin) 6 years ago
I have an old Chinon M42 mount lens - so all I need is an adapter - will any of them on ebay do the job and therefore should I just go for the cheapest (as they are probably all made in the same factory)?

Or is it better to pay more for one with a chip (which I believe gives focus confirm and also makes the steadyshot work??)

(mod. edit: Removed ebay link)
Pedro del zurdo 6 years ago
@Mellowmark: When I was looking at using M42 lenses, there were 2 ebay sellers that advertised a "programmable" chip service.

On occasion they programmed the chip with incorrect settings, however they've very quickly sent out another ( from hong kong )

I find the "programmed" adapters work well - for example I have 3 in use just now, one on a Tamron 500mm mirror lens - which I get focus confirm very easily, another on a pentax 40mm pancake lens ( which I had to adapt the mount ) and another on a Helios 44 58mm Russian lens.

p.s. Its not a 135mm f2.8 by some chance is it?
mellowmark 6 years ago
@Pedro del zurdo Thanks, will look into that - it's not a 135mm f2.8 no, it's just a humble/common 55mm f1.7 so I don't want to spend too much.

It's a decent lens but not an expensive one and I already have the SAL 50mm so I am kind of covered for a prime at that focal length already.

Of course there are lots of other nice M42 lenses I could buy if I had an adapter though. :)
Arkku PRO 6 years ago
The question of varying adapter quality and the benefits of chipped adapters are discussed at some length in the original post (which is why this is the M42 FAQ). In short: there are differences between adapters, but they do not necessarily correlate with price, and with a chip you get AF confirm + SteadyShot – whether these are worth it I think only you can answer. =)
PelleMn 6 years ago
I got my M42 adapter yesterday. I bought it from eadpt.com/eadpen.htm (JamesLao T) since that was the obvious recommendation I found on the web . Guess how disappointed I was to find that it doesn't fit on the camera body (Alpha 77)!
Without great force it can only be rotated a narrow angle, far from reaching the locked position. I have pictures of it here: picasaweb.google.com/PelleModen/M42AlphaAdapterProblem?au...
It is also black without any surface finish rather than glossy as on their web page. Have they switched to low quality mechanical stuff?
Mr Nessy 6 years ago
No idea about your adaptor, quality usually varies on these things, but don't do anything that requires "great force" to your camera. That's never good.
Arkku PRO 6 years ago
PelleMn: I would suggest contacting the seller about this problem. If you wish to discuss the matter here (although I doubt anyone can help if the adapter doesn't work) then please start another thread for such a specific question – this is the M42 FAQ thread.
PelleMn 6 years ago
You are right Arkku. Of course I have contacted the seller, hoping to get it replaced. If not, are there any other sellers that provide AF confirm and image stabilization information to the body for focal lengths that you specify? For the ones I found on eBay, I didn't see that. I planned to use it mainly with my 105mm and 300mm lenses.
Arkku PRO 6 years ago
I think a seller called big_is or something along those lines offers custom focal length adapters on eBay.
KaneDWilliams 5 years ago
I would like to say that all the Big_is adapters I have bought have failed in no time at all. In many cases, the pins have scrapped off the chips as soon as they have been put on the camera, sometimes this wearing down has take a few months to ruin the adapter.

They have now changed their design due to my feedback, and they sent me a new one to try and it did not register at all, although the pins did not scrape against the chip.

The company are very helpful and have sent many replacements and refunded me for one or two, but I am still out of pocket and have adapters fitted that the chips are useless and still make me cringe when they scrape against the pins.

My camera is an SLKT-A65V, so may be with other Sony's it will be fine?

I have written to Sony to suggest they add the facility to be able to tell the camera that a lens is attached and what it's focal length is, thus doing away with the need for chips at all. If you think this is a good idea, write to Sony and suggest this firmware update.

KaneDWilliams 5 years ago
Btw, I have a Mamiya Sekor 55mm 1.8 that will not achieve infinity focus on my SLT-A65. It is also very hard to alter aperture with the adapter fitted, as it seems the aperture ring it right up against the adapter. Anyone else have this issue and worked out a solution?
Capt Kodak PRO Posted 5 years ago. Edited by Arkku (admin) 5 years ago
@KaneDWilliams: The Mamiya "M42" mount lenses do use the same basic design, but if you look closely, you'll see they have a slight lip on the back of the lens on the aperture ring that prevents it from fully seating on your adapter--or any other M42 mount camera for that matter. It causes the lens to stand off a millimeter or so, but just enough to prevent you from getting infinity focus. The old Mamiya SLRs that used those lenses had a ring at the mount that allow it seat all the way--kind of like a socket. Some folks have taken and filed off the little lip and others have trimmed down their adapter, but it's a lot of work for a lens with just middle of the road performance...

I have one in my camera collection and, no, I don't use the lens on my Sony...
JamesRWyper 5 years ago
I've used an adapter from big_is for a couple of years and never had a problem with it. They also sell a version under seller name weakpotoman on ebay "without flange" for Takumar lenses which also don't sit properly on regular adapters, this might work better with your Mamiya. The only difference in the listing title is the price (about twice as much) but the description (eventually) gives more detail.
KaneDWilliams 5 years ago
My MS lens is not an SX one, so don't think it has the 'lip', but I'll check.

As for the specific Takumar adapters, I was sent one from Big_is for a SMC Takumar 28mm 3.5 and it did not work. I then put on a standard adapter, not made for Tak's and it worked with infinity focus! Just goes to show, nobody's experiences are the same.
Arkku PRO 5 years ago
Almost all adapters are “Takumar compatible”, only the (quite rare) ones with an extra flange to press in the auto-aperture pin on auto-only lenses are problematic with (some) Takumars (since Pentax implemented their open-aperture metering by adding protrusions inside the lens mount, rather than outside like e.g., Mamiya and Fuji).

As for problems with the Mamiya lens, I don't think you can get any adapter to help with that—based on the description “it is very hard to alter aperture with the adapter fitted” the lens definitely has a protruding aperture ring (the whole ring, no specific protrusion).
hansd.alt56 4 years ago
Hi Kimmo,

you wrote

"Problematic lenses are those that have auto-mode only. For these problematic lenses there are some adapters with an additional metal “lip” which presses down the aperture pin (all the time). These adapters solve the issue for auto-aperture-only lenses, but aren't compatible with all lenses because some won't physically fit in all the way due to the lip. "

That's exactly what I need because I don't want to modify THIS lens with your fine "swab solution" - which I tried successfully with a Helios 44" - but use it also with Practica, Zenit etc.
(You may take a look at my fotostream).

After searching a longtime for any results I would be very grateful for hints where to get such adapters.

Greetings from Germany
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