Not getting infinity yet. I am just hand holding all the adapters and lens parts together and looking through the viewfinder. The close and medium focus views look nice!
I am sanding the two mounts as a pair (see above post photo) and the back of the aperture ring. I think I have sanded off quite a bit of material but I am not at infinity yet. One problem though: the four screws are now too long after all the sanding. I am trying to carefully shorten the length of the screws with a Dremel. But I might need fresh screws or make deeper screw holes.
The more I sand down the mount adapter setup the shorter the screw holes will be. I am also getting close to the three side screws on the ring that goes around the main aperture back ring assembly. See photo: one of the side screws is circled in red.
I think I am done for one day and will get back to it in the morning. I think this is going to work though...
I have not worked on the 35/1.8 or the 21, but, on all the conversion I have done so far I have taken off .5mm from the bottom of the M42 adapter without a problem. But then Minolta throws in some uniqueness into every lens mount it seems.
I just looked at Max's photo again and your description and think I understand what you are saying now.
On this style Minolta lens mount, with the silver ring, they make it a bit easier.
I take off .5mm from the M42 adapter, glue the adapter to the Minolta chrome mount. Either remove the ridge that centers the Minolta chrome mount or allow space for it in the base of the M42 adapter. Then the two glued mounts will sit flush on the aluminum .
Screw the two mounts as a unit on the lens. Attach the silver ring to the lens - you have to make the hole in the ring a little larger to clean the M42 adapter.
Try to fit the lens on a Canon body. Most likely it won't fit, you cannot rotate to engage the bayonet. The silver ring is a little too thick. I sand it a bit and try again until it just mounts on the camera. That way it is a nice tight fit. On one lens, the 28/2, the silver ring did not have to be sanded at all.
The silver ring only affects the tightness to the Canon body, not infinity. Taking the .5mm from the adapter is painless in the lenses I have converted, but I have not done the 21mm, yet, maybe.
Rodney
Ed Sawyer wrote:
I'll try to post it tomorrow. It's mainly numbers like the rest, but at least can be compared to the Oly numbers.
Max you are making headway. the hogging out and fitting of the two rings together is the hard part.
Rodney, you cant' take the .5mm from the M42 flange, it has to come off the lens aperture piece in this case, I think. If you take it off the flange, the bayonet (eos) will too shallow to seat on the camera I'd think.
in my conversions, I remove the flange on the M42 and bring it down to flush so it adds no depth to the whole package. then I take the .5mm off the backside of the apeture piece, where the original minolta bayonet screws on. I think that's the only way to do it, at least or so it seemed to me when I was doing the 35 1.8s.
Tariq - that is the test, yes. Look at the contrast numbers though! very high. indeed, probably not distagon level but the price isn't either.
Max - you are getting there, that's the right procedure. Cut down the screws with a dremel if need be, or use washers behind them, there should be enough room in the apeture mount piece to allow the screw heads to stand proud a bit. Don't think to try tapping the minolta bayonet deeper- that is a recipe for disaster. not only would you have to enlarge the holes then tap larger screws in , but it's very hard to find taps that small, and even harder to use them with snapping one off. Trust me.
Rodney - your method would work here too but the silver ring has not much material, taking off .5mm may be too much to allow the screwholes to still seat - hard to say. it's damn close though. Also this ring is not solid, but more of a U-channel or L-channel profile, and fragile. If it were solid it would be less of an issue. But your method is basically the same as what's happening here.
Hmm. I wonder if the solid trim ring from a 58 1.2 is the same diameter. if so that could be a useful alternative, possibly...
The bitch is that the trim ring needs to go on after the lens apeture piece is put back on the main lens body, otherwise you could epoxy it onto the apeture piece, sand them both down together, and not worry about if you go below the level of the radial screws.
I will start my one of these soon.
BTW, I looked closely at this lens yesterday and am not 100% convinced it's a floating element design...
PhotoMaximum wrote:
I am sanding the two mounts as a pair (see above post photo) and the back of the aperture ring. I think I have sanded off quite a bit of material but I am not at infinity yet. One problem though: the four screws are now too long after all the sanding. I am trying to carefully shorten the length of the screws with a Dremel. But I might need fresh screws or make deeper screw holes.
The more I sand down the mount adapter setup the shorter the screw holes will be. I am also getting close to the three side screws on the ring that goes around the main aperture back ring assembly. See photo: one of the side screws is circled in red. ...Show more →
Max, good work!
Just a couple thoughts. If you take a look at what parts of the Minolta lens back faces with the EOS camera mount face, it is an extreme outside radius of the Minolta back, specifically that grey ring with the 3 radial screws.
Rodney's comment pointed to that fact, as he suggested taking off optical path or thickness from the M42-EOS adapter, first, as that accounts for about 1.5mm. If you don't, then you are 1.5mm too thick to start with, not to metion the quoted .5mm register difference.
The thing you want to watch out for is that grey ring with the 3 radial screws. It has a thin lip that seats with the lens body and acts as something of a washer. If you sand thru that, the lens seat may not be solid as now you are then dependent on just those 3 radial screws to set the ring face at an exact position.
Bottom line: If you don't account for the 1.5mm thickness of the M42-EOS adapter, you will need to eat away 1.5mm of the Minolta back assembly before fine tuning the -.5mm removal to get to infinity focus on a floating element lens that doesn't have infinity adjustment screws.
When I say that I have to sand the silver ring (with 3 set screws), it is only a few thousands of an inch so it will mount on the Canon body. That does not create any problems with the integrity of the ring at all.
Ed Sawyer wrote:
Tariq - that is the test, yes. Look at the contrast numbers though! very high. indeed, probably not distagon level but the price isn't either.
It does show sharpness falling off into the corners and some vignetting even at F8. According to the MP test, F11 is optimal I guess.
The issue for me is that the 5D is already testing this lens so my a900 would test it even more. I am only finding this lens for around $400 at the moment which is another factor. Finding a really exceptional 20-24mm lens for the a900 is becoming difficult but I may give this lens a try if I can locate one at the right price.
Be patient, I got mine for $175 which I think was a decent deal. Of course I hope the final conversion and infinity focus works. Looking through the 21 in a room (not at infinity) looks promising so far though...
PhotoMaximum wrote:
Be patient, I got mine for $175 which I think was a decent deal. Of course I hope the final conversion and infinity focus works. Looking through the 21 in a room (not at infinity) looks promising so far though...
$400 is not *too* bad... any of the Oly 21s are at least that...
still, indeed it can be found for less occasionally.
Jim, good points. However I don't think this lens has floating element construction (though I could be wrong, and would like to be wrong!), but if it does it's not the typical canon pseudo-floating element which is really just a fixed rear element and then linear group focus of everything in front of it. The rear element moves in and out on this lens, as the focus changes.
has anyone confirmed there are not any focus helicoid adjustment screws anywhere?
And the quote on this lens: The Minolta MC W. Rokkor 21mm f2.8 was one of the best ultra wide angle lens made by Minolta and was the first to use a complex "floating elements design" (12 lens in 9 groups). It was annunced on the market on 1973 (first version on 1966) it looks as an impressive piece of glass and metal (it has a great solid construction !). It was one of the best wide angle, on 20-21mm range, with very hight optical performance second only to the "Zeiss Distagon 21mm f2.8.
A lens that is very difficul to find on the used market as its optical quality that is simply marvelous....Show more →
