Topic: Lens modification project

[JJJ]

Hello Dogs,

Time for a new optical project!

I have today acquired an interesting old lens...   A Sigma 28mm f/2.8 - manual everything, which is quite nice really - and in Minolta (MD) mount.

The lens cost me $19.  I probably won't be buying a Minolta (/Konica / Sony) camera any time soon, so for a bit of fun, and to (hopefully) get a nice manual prime, I am going to convert it to Canon EF mount.

Because of differences between mount and sensor/film - I can't just use a straight adaptor (without introducing a crop factor, and not being able to focus to infinity anyway), and I don't like the idea of adaptors with optics in them.

So, my plan of attack...   

*Purchase an EOS to M42 adaptor (this is on the way already).  M42 is a screw thread style mount - so you can think of the M42-EF adaptors as more or less an EF mount.
*Dis-assemble the MD mount currently on the lens. (I have already done this... it seemed fairly straight forward - the aperture lever came off with the mount which is nice)
*Remove any tabs which might be in the way. (or better, cut the adaptor to suit)
*Drill holes in EF-M42 adaptor to suit existing screws used on MD mount
*Re-assemble with EF-M42 in place.

Mount/Enjoy

A guy on flickr has already done a similar process - http://www.flickr.com/photos/asbalyan/sets/72157603494868864/
Another guide is here -> http://www.pbase.com/kkawakami/mctoef_mount_conversion
I'll be following the same sort of guidelines - but hopefully will do a neater job!

I really like the idea of picking up old, good quality glass and being able to use it on my modern body.

Has anyone attempted anything like this?  Pics/Progress to come.

[Arghdee]

Sounds interesting.. Obviously, keeping swarf/dust/zebra hair out of the lens will be important...

[JJJ]

Yes and no... the mount is separate - you can think of it as an attachment to the assembly which holds all the optics.  So in that respect, I don't have to be too careful.

Also, because it's a Sigma lens - I'm sure it was designed to take a few different mounts from the beginning.

In terms of swarf - the bits I grind (if any) won't be near the lens at all when being worked on.

[JJJ]

I've had a bit of progress today...

My M42 - EF adapter has arrived - and I've taken a few pics:

The lens with original Minolta mount attached


Bit of a look at the lens...


Rear end with MD mount removed


My new EF mount sitting on top of the lens


Same again, from a different angle.


... So from here - I'll have to remove the pesky tabs, or cut holes in my mount to make room for them.  I'm still not sure which to do.

After this - drill holes in the appropriate place for the three screws to go through my new mount and in to the lens casing.

Check for focus - maybe shave down the mount a bit, or add a spacer depending how this goes.

[Arghdee]

Relief holes for the tabs is a neater solution.

[JJJ]

Yeah, for sure... Might have to pick up a Dremel.

[Dartman]

Yeah, make holes, less chance of destroying a good lens getting it full of debris. If you mess it up you can always get another adapter and try again sometime.