Photoclubalpha

Been searching e-bay for old Minolta primes that could work on the Alpha series with, for instance, the M42 adapter. Is it only the M42 lenses that will work like this. I assume if a lens is bayonet fit there's no way it can work, are MD's bayonet?.

As a related point of interest I saw this lens

http://cgi.ebay.co.uk/MINOLTA-MC-ROKKOR ... 2c528c7e9c

and was curious about it's apparent value - although the listing does say 'this is the rare one', is it just that - a hard to find lens?

That MD58 f1.2 was a class lens by all accounts, but I have reservations about how the MD's would perform in front of a digital sensor (reflections), but apparently it was very highly regarded on film.
Minolta changed the AF bayonet mount design so their MD lenes won't fit directly without an adaptor, (there is a lever pin on the MD lenses that projects slightly further into the mirror box and will collide with the mirror on an AF camera, even if it did fit).
I've seen discussions on the value (or not) of adapting the MC, MD lenses for use on AF cameras, especially digital cameras, you have to use an adaptor with glass elements in it to retain focus infinity, with the penalty of a slight change in focal length and light loss, plus image degredation due to the elements in the adaptor possibly not being of the same quality as the glass in the lens itself.
Otoh I have seen some very good images taken with MD lenses (and other MF brand lenses) on digital cameras, so it's really comes down to being a case of 'suck it and see' I think.
Just remember there is no AF and no communication between camera and lens, so the camera has no idea what focal length lens is being used (for Auto exposure, AS/SSS, flash ADI calculations etc.) there is no auto f-stop iris closure as the actuation is non-operative, the f-stop is set on the lens (in MC, MD vintage), so it's a case of focussing wide open manually, then closing down to the f-stop (the view will darken beyond f5.6) you want before you shoot, having preset the camera to the corresponding f-stop beforehand, as well as the other exposure values...shutter speed, ISO, camera in M mode.
Greg

Thankyou Greg. I find myself wonering if it would be possible to literaly cut off the bayonet/pin that would interfere internally on a DSLR.

But onward.. it seems clear browsing ebay ads that a lot of lens sellers have no real clue what they are selling so I have a further question for the experts on here. If a lens is M42 and I have an M42 adapter does it follow the two can be married? I ask because some of these ads say specifically, for instance, canon or nikon etc..

I'm particularly interested in trying a zeiss sonnar/jena 135mm but wonder about Russian copies of said design such as the Helios, as a prime it could be every bit as sharp or sharper than the cheaper modern zooms?

the problem isn't so much the coupling pin but the registration distance. the SR (MC/MD) mount had to be closer to the image plane than the Alpha mount will allow. It's more than the diferent mount it's where the lens winds up when its mounted. With the lens on the adaptor and focused at infinity the lens still has to be physically closer to the sensor to be in focus. Thats why the correction element in the adaptors and why without it there is no focus at infinity.

The Adaptall adaptors work without an element in them and so do M42 because the registration distance on those systems was greater, not less than what we have now with the SR mount.

The differences are just too great to ever get an MD lens bayonet (modified), to mount successfully directly onto the AF A-mount, even the AF drive shaft would interfere, yes it's springloaded, but the camera 'knows' when the AF drive shaft is correctly aligned and engaged with the AF drive socket in the AF lens, something that would not happen with an MD lens, so the AF drive shaft would remain depressed and un-engaged and as far as the camera is concerned this would be regarded as an error and most likely stop functioning.
The adaptors have a recess as far as I know to allow the shaft to falsly 'engage' and fool the camera.
Greg

Thanks for replies guys. So I now know I'm limited to looking at M42 mounts, but are there different M42 mounts? Some e-bay sellers seem to think so, a listing included the following

Pentacon 50mm F1.8 MC auto lens for Pentax M42 and Canon EOS in near mint condition.

As someone who is still in the process of learning I read that and assume, 'right, that won't fit my camera then', but I also suspect I'm probably wrong and that the seller is in a similar state of ignorance as myself.. Can anyone tell me more about the M42 mount. Thank you very much.

Problem solved, good old Wiki came through for me.

http://en.wikipedia.org/wiki/M42_lens_mount

I now feel confident bidding for any M42 lens in respect of fitting. In respect of is the lens any good, haven't got a clue.
So feel free to keep chatting about M42 lenses, wether by reputation or through personal experience. Thanks all.

It's a lot of fun using these manual lenses, some are better than others but there are some real gems out there. While your waiting for stuff to arrive research "stop down metering" then you you get it hooked up you'll understand how to shoot with it.

The MD and AF mounts have an identical back focus register. Minolta did this to avoid changing too much. It means that with certain MD/MC lenses - for example the 58mm f/1.4 MC - you can simply unscrew the mount, take an AF M42 adaptor or the mount off an old AF lens, and create an AF-fitting manual lens. It is necessary to remove the aperture actuating pin.

It does not work with all manual lenses. I have two in front of me now, MC 50mm f/1.7 and 200mm f/4.5, which have a different way of fixing the mount with screw in the side. But I have a 28mm f/2.8 MD which looks as if the MD mount could be unscrewed and an AF adaptor with suitable holes drilled fitted in place.

Because the back focus is similar (within 0.1mm) any adaptor which goes between the manual lens and AF body will prevent infinity focus. Most are therefore made with glass converter elements (1.2X) and also ruin the optical quality of the manual lens.

You can adapt any Pentax/Praktica thread lens to AF using an M42 Adaptor for Alpha. Those for Canon and Nikon are of course not suitable (they adapt M42 lenses to fit Canon or Nikon). You should buy an AF adaptor with focus confirmation, ideally matched to the focal length of lens. You can get an adaptor ready set up for 85mm, 135mm etc. Some of them are very badly made and don't fit the Alpha bodies well. The black ones with focus confirm chips are best. Some alloy (silver) ones will either jam on the body, or foul the internal mechanisms of the Alpha.

Manual M42 lenses are safe. Auto M42 lenses may have a long FAD pin which could foul parts of the Alpha body internals, this can either be shortened (leaving the lens fully operative) or glued in or removed (turning it into a manual only lens.

David

I though the SR mount was 43.5 and the A mount was 44.5?

David Kilpatrick wrote:The MD and AF mounts have an identical back focus register. Minolta did this to avoid changing too much.
David

When you remove the mounts, if there's 1mm in it (which I do not think there is - the various tables of back focus distances show some leeway) it makes little difference, you have to shim the fitted AF adaptor when converting the lens.

As far as I can tell, the optical back focus (where the rear element sits in a typical comparative design) is the same but there's more stuff inside the AF mount throat to interfere with bits of the lens mount. I am not sure which old lens to hack up.

David

For best results with MC/MD lenses follow these simpleimstructions!hiccup!
http://www.pbase.com/pganzel/modificati ... f12_rokkor
All you need is an AF mount....
And this was taken with a Minolta MD 50mm macro on my 7D using an adapter.

I have three lenses that I'm using in different situation. the 58mm 1.2, the 50mm 1.2 (sharper than the previous one, better flare control, less vignetting, but a little less beautiful out of focus effect) and the marvellous 135mm F/2.0.

All the three lens has the back MD lens with 4 screws. This is the first things to check when you are targeting to modified the lens.

After that Is to be sure that the back metal lens with the 4 screws it thigh with the support that will connect to the lens. If it is not, you will have to much modification to do to make it comfortable with a M42 confirm focus adapter.

Is is possible that you will have to create a offset of about 1mm or more depending the design to make the focus distance ok, instead of that you become with a lens that focus more than infinity and less close to your subject. In this situation, it is possible that you will have to find a longer screw. But for the moment I can tell you that for the 58mm 1.2 it is not the case, but the 50mm 1.2 and 135mm 2.0 is very tight with the original screw.

There is also good Soligor, Sigma and other third party brand who have created lens for MD mount, and usually those one are easier to modified (using the standard 4 screw mount).

Here link of pictures taken with the A900 for the 58mm, 200mm Soligor and 135mm :
http://www.pbase.com/nadeauf/58mm_f12_on_a900
http://www.pbase.com/nadeauf/soligor200mmf28
http://www.pbase.com/nadeauf/greatminoltalens

Usually this is only the last version of the MD that are the easier to modified, the one with complete black metal back with the 4 screw. Avoid all the model that have chrome metal ring with screw only on the side of the barrel of the lens.

Regards,

Frank

Other thing, usually all the Minolta MD lens I have modified or tried to modified has the good feature of if you removing the Aperture control system that is usually connected to the camera, the aperture is by default closed and will follow the control ring on the barrel of the lens. Inverse behavior will be to complex to adapt for AF system.

And also, I have just verified, and the 58mm 1.2, has 8 screws on the back, but only 4 are longer screws, so the 4 other are not needed to adapt your M42 AF adapter.

Regards,

Frank