I converted two lenses from the 1960's to Canon EOS... total cost $40 including the lenses. No corrective glass is used. The spacer on the rear of the lens was lathed down to match Canon specs. Took about 1 hour for the 58 mm and 2 hrs for the 135 mm. I LOVE the glass!!!
Rokkor-X 58 mm f/1.4 near
Rokkor-X 58 mm far greatly reduced size and quality due to website upload restrictions but you can see that the lens does get to infinity. rather well.
Rokkor-X 135 mm f/2.8 + 26 mm extension tube near house fly on ragweed
Rokkor-X 135 mm far infinity focus obtained.
Minolta focal plane is "close" to Canon. Canon uses 44 mm and Minolta used 43.5mm. On these two lenses, there is enough meat on the rear spacer to trim down 0.5mm + the thickness of the EOS to M42 adapter (1.45mm) That moves the rear of the lens into the 43.5 mm from the sensor. On crop cameras like mine Canon EOS SL1 (D100), no other modification is required. If you are using a full frame camera then the rear lens element must be removed and lathe off 0.5 mm to the lens barrel to clear the mirror when lifting up to take the pic. I looked at the Rokkor 50 mm f/2.0 which is also very nice glass but there is not enough metal in the spacer to save its aperture functions and get to infinity but it will still make a nice portrait and macro lens. I am sure I could create another way to spring return the iris but even with the spacer completely removed, it is still to far away from the focal plane with the adapter plate inbetween the lens and the camera body.
I also purchased EOS to M42 adapters that have a autofocus confirm chip that is programmable to the specifics of the lens it is attached to. You still have to manually focus but the red light will blip in the viewfinder to confirm you are focused spot on. The neat part is that the AF confirm chip is programable simply on the camera body by just snapping a pic at the proper f/setting f 47, f45, f 46 then at the right ones to program your lens specs and you are set to go. On the M42 adapter, the threads need to be lathed out to clear the mechanics of the aperture arm so you are widening out the the spacer from 42 mm to 44 mm. Now it is just a EOS mounting plate. Use the rear Minolta spacer to line up your drill holes and countersink so the attach screws are flush with the plate.
After you have confirmed infinity focus you are set to mount it permanently. If you lathed out a bit too much metal out of the Minolta spacer, you can make a shim out of simple aluminum foil. 1 layer of foil = .03 mm so if you went over by 0.12 mm then add 4 layers of foil. 4 to 6 dots of JB Weld epoxy on the spacer once all the measurements are confirmed will lock down that setting forever.
What are the advantages?
1. Clear glass at near or equal Cannon L glass quality
2. Wonderful color rendition
3. Excellent Bokeh
4. A precise focal ring....the Rokkor-X 58 mm goes 3/4ths the way around the barrel. 135 mm goes 360 degrees around from near to infinity. My Canon 50 mm f/1.8 has no depth gauge and very corse manual focus of 1/4 barrel of turn. If I can manually focus with it, it is by chance it is correct because by just letting go of the focus ring changes the focus.
5. did I mention cheap? I purchased used a 58 mm, 50 mm, 135mm, Vivitar 70 -150mm + the Minolta camera + a Canon camera bag for $25. I also converted the Vivitar 70-150 MC mount but it's mechanism to operate the iris is such that there is no good way to reduce it without damage so I make it a macro- portrait lens. Even though it doesn't go to infinity, what it does do is still great stuff. (pics below)
These pics were from the Vivitar 70-150mm f/3.5 adapted to Canon. These are reduced pic sizes download from my facebook page but it still shows some great color rendition.
Should these be done in place of Canon lenses??? Nope. Canon makes some excellent lenses but some of them cost more than a used car each and out of the price range for the novice. Making conversions like these gives the photographer an ability to hone his manual skills, have fun, experiment and not break the bank doing it.
I have read the comments of many in this thread saying that it is not worth the trouble. They may be right from their perspective of just get it and it works no matter the cost. The way I looked at it ... the most I could do is to mess up the lens and it was only a $6 investment at risk. Research your lens candidates, visit You Tube for clear instructions on how they converted theirs and you will find some wonderful old glass out there just begging to be re-tasked.
Bob Komjathy R.Ph.
