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My first Rokkor conversion...please help!
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PostPosted: Sat May 15, 2010 4:27 pm    Post subject: Reply with quote
Arkku wrote:
bawang wrote:

I took the DIY route with M42->EF adapter with my first copy. It worked but it is irreversible job.


What did you have to do that's irreversible? I converted with an M42->MAF adapter, and it's reversible.


On reversing a modification... I don't really care. I'll never go back to film, so for the few people that do want to use the old film cameras, there will be plenty of unconverted lenses available.


PostPosted: Sat May 15, 2010 7:22 pm    Post subject: Reply with quote
woodrim wrote:
peterqd wrote:
woodrim wrote:
As for the issue of damaging the lens, as long as you do it right, it will be of more value. The old Minolta mount isn't coming back and the lenses will have no life other than digital via conversion.

Do you really feel the value is increased? I'm sorry but I would never dream of buying a lens which some amateur has been hacking about.


Arkku covered the issue very well, as he usually does. I do want to point out that I said "as long as you do it right", as with anything, a good job will always be worth more. What Buchannon is doing with Minolta for Canon is admirable - and it allows reversal.

I think you would probably know that each lens is tested and calibrated before it leaves the original factory, and with an extremely high degree of precision. It is important, for example, that all the elements are optically centred properly and exactly perpendicular to the face of the mount. If they aren't the optical quality will suffer and focus accuracy will be variable across the frame. I am sure Jim Buchanan's work is carefully done, but I doubt it's to the same accuracy as the original manufacturer.

However, I was referring to some of the awful conversions I've seen here on the forum, done with a handheld Dremel grinder and handheld drills, countersinks etc and no machine tools used at all. The accuracy of the original mount has inevitably been lost, and that's what I meant by "completely ruined" and why I would never buy a converted lens. I don't see the distinction between using a converted lens on a film or digital camera, it will never be as accurately set up as it was from the factory. I stand by my words and I don't agree it was an overstatement.


PostPosted: Sat May 15, 2010 8:24 pm    Post subject: Reply with quote
peterqd wrote:
It is important, for example, that all the elements are optically centred properly and exactly perpendicular to the face of the mount. If they aren't the optical quality will suffer and focus accuracy will be variable across the frame. I am sure Jim Buchanan's work is carefully done, but I doubt it's to the same accuracy as the original manufacturer.


Lens manufacturers don't possess any magical powers with which to make their lenses. They do possess special equipment to check for things like the flatness of surfaces, which most DIYers do not. However, it's not much of a trick to use a lathe to get a surface flat enough the tiny imperfections are well beneath the limits of the resolution of the lens and camera.

Most users on this forum use adapters on their lenses—i.e. they convert the lenses to other mounts with (usually) low-quality add-on mounts. There is no real difference to attaching a new mount with screws; we just call these adapters due to the ease of installation. Have you ever heard any complaints about these adapters introducing visible tilt or shift effects? The only common complaint is lack of infinity focus accuracy, but in most of my lens conversions I've adjusted infinity focus using the mechanism built into the lens by the original manufacturer for exactly this purpose. So, converted lenses are often better suited for use on the new system than adapted ones…

(I can personally attest to improving infinity focus position accuracy on several of my converted lenses. Including the Minolta Rokkor.)


peterqd wrote:

However, I was referring to some of the awful conversions I've seen here on the forum, done with a handheld Dremel grinder and handheld drills, countersinks etc and no machine tools used at all. The accuracy of the original mount has inevitably been lost, and that's what I meant by "completely ruined" and why I would never buy a converted lens.


Loss of accuracy depends on what the tools were used on. For example, if they were used to remove an aperture-coupling mechanism, it has no effect on the accuracy of the mount. (Of course, such a conversion is irreversible.) Still, it seems to me like you first went back to specify “some awful conversions” and then again generalise that you would not buy (presumably) any converted lens?

You may be shocked to learn that extremely rare and expensive Zeiss 50mm f/0.7 lenses were converted for use in Stanley Kubrick's film Barry Lyndon! The conversion even included hacks like altering the innards of the lens to fit movie cameras. Completely ruined!

http://www.visual-memory.co.uk/sk/ac/len/page1.htm


PostPosted: Mon May 17, 2010 2:20 pm    Post subject: Reply with quote
Hey everyone,

Did a search on this topic and this seems like the best thread. I have two MC Rokkor 58mm 1.4 lenses.

I've fairly crafty and decent with shop tools, I have a precision drill press etc. but I don't have a metal lathe.

About the only think I can find on the net concerning the conversion of these lenses to EOS mount is here: http://www.4photos.de/camera-diy/minolta-rokkor-58-to-canon-eos-conversion.html

Does anyone else have any input or links to DIY version of the conversion. I have been in contact with Jim Buchanan and right now his adapters are $75 shipped. He did mention I could perform a DIY mount by buying a M42-to-EOS adapter for about $10 and indeed I've found them from about that price.

Thanks,
Roy


PostPosted: Mon May 17, 2010 7:56 pm    Post subject: Reply with quote
motleypixel wrote:

Does anyone else have any input or links to DIY version of the conversion.


This guide shows how to convert the MC Rokkor 58mm f/1.2 to Sony/Minolta AF. EOS conversion should be exactly the same except you use a different M42 adapter as the replacement mount.

However, there are many different versions of the Minolta lenses, so the 58mm f/1.4's may or may not be different. I wrote about some possible problems in this thread.

Last edited by Arkku on Tue May 18, 2010 2:02 pm; edited 1 time in total


PostPosted: Tue May 18, 2010 12:09 am    Post subject: Reply with quote
Given the time required and aggravation, the $75 sounds cheap.


PostPosted: Tue May 18, 2010 2:05 pm    Post subject: Reply with quote
woodrim wrote:
Given the time required and aggravation, the $75 sounds cheap.


It depends; some of us enjoy doing stuff like this. =)


PostPosted: Wed Jun 16, 2010 10:53 pm    Post subject: Reply with quote
motleypixel wrote:
...
About the only think I can find on the net concerning the conversion of these lenses to EOS mount is here: http://www.4photos.de/camera-diy/minolta-rokkor-58-to-canon-eos-conversion.html...


Please ask if something is not clear enough on my website!
I have some more photos if needed.


PostPosted: Wed Jun 16, 2010 11:35 pm    Post subject: Reply with quote
Well I finished converting Minolta 58mm 1.4 MC to sony A mount today. I found this lens easier to convert than minolta 50mm 1.4 MC. I haven't tried minolta 50mm 1.4 MD so cant comment on it.

Best way to convert is to use M42-->Minolta A adapter (EOS adapter in your case). This particular lens is almost similar to Minolta 58mm 1.2 MC which was converted by Arkku. You can follow his guideline on flickr after that. This is the easiest way in my opinion.


PostPosted: Wed Jun 16, 2010 11:37 pm    Post subject: Reply with quote
Arkku wrote:
woodrim wrote:
Given the time required and aggravation, the $75 sounds cheap.


It depends; some of us enjoy doing stuff like this. =)


I second it .. Very Happy
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