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My first Rokkor conversion...please help!
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PostPosted: Thu May 13, 2010 7:53 pm    Post subject: My first Rokkor conversion...please help! Reply with quote
Hi Guys,

I've got as far as ordering the 50 & 58mm lenses of choice, but for some reason and despite lots of Googling and forum searching, I need to ask the stupidest question.

...without a donor lens for a mount, where would I find an EF mount? alternatively, where do people shop for donor lenses?

thanks,

John.


PostPosted: Thu May 13, 2010 8:01 pm    Post subject: Reply with quote
Our member Koji has done it, here's his page.
http://www.pbase.com/kkawakami/minolta_mc_to_ef_mount_conversions

Or you could get a conversion kit from Jim Buchanan
http://www.jimbuchananspace.com/Camera_Services.html

Even better, why don't you convert your horrible plastic camera instead of damaging these lovely lenses? Wink Seriously, Koji has done it with one of his cameras, you can find a thread on this forum somewhere.


PostPosted: Thu May 13, 2010 8:23 pm    Post subject: Reply with quote
I seriously thought about it - however I simply don't have the funds to add another camera to my collection and need to use the 17-40L on it for product shots & other photography work that comes in as a side effect of my web development business.

(the flange change)

thanks for the links!

J


PostPosted: Thu May 13, 2010 11:43 pm    Post subject: Reply with quote
The simplest source for mounts compatible with modern cameras are flanged adapters, e.g. for M42 or QBM. Get a flanged one without glass, disregard its function as an adapter and use the mount on the other side for whatever you need. The flange is easy to drill holes into.

Here's an M42 to Minolta AF adapter installed on my Rokkor 58mm f/1.2:



(Linked from the photo is my guide to the disassembly, conversion, and infinity focus adjustment of this lens. Note, however, that many of the other Rokkors are slightly more complex to convert, especially if you want to be non-destructive.)


PostPosted: Sat May 15, 2010 12:42 am    Post subject: Reply with quote
Very simple, you buy a m42 to EOS adapter and adapts. It is the cheapest. Wink


PostPosted: Sat May 15, 2010 1:13 am    Post subject: Reply with quote
Well, not really that simple. Not all Minolta lenses have the same type mounting flange arrangement, and Getting the register correct will be a challenge. Considering time, a donor M42 conversion ring, and aggravation, you might be better off with one of the (albeit expensive) Buchanan conversion kits. I wish there was one for Minolta to Sony.

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.


PostPosted: Sat May 15, 2010 2:42 am    Post subject: Reply with quote
woodrim wrote:
…conversion kits. I wish there was one for Minolta to Sony.


Check with Pete Ganzel, he's been making replacement mounts for specific Minolta lenses.


PostPosted: Sat May 15, 2010 3:05 am    Post subject: Reply with quote
You could also get a Macro lens reversal ring, which is pretty reasonable.


PostPosted: Sat May 15, 2010 4:31 am    Post subject: Reply with quote
woodrim wrote:
Well, not really that simple. Not all Minolta lenses have the same type mounting flange arrangement, and Getting the register correct will be a challenge. Considering time, a donor M42 conversion ring, and aggravation, you might be better off with one of the (albeit expensive) Buchanan conversion kits. I wish there was one for Minolta to Sony.

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.


Getting the EOS mount, if simple, the adaptation depends on which lens is.
Will always need a lathe to cut the original ring Rokkor. EOS 44m, 43.5 Rokkor.


PostPosted: Sat May 15, 2010 5:56 am    Post subject: Reply with quote
francotirador wrote:

Getting the EOS mount, if simple, the adaptation depends on which lens is.
Will always need a lathe to cut the original ring Rokkor. EOS 44m, 43.5 Rokkor.



+1
the nearest flange back, the best result ...

tf


PostPosted: Sat May 15, 2010 9:02 am    Post subject: Reply with quote
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.

Admittedly, as a craftsman, for me it goes against the grain to see all that beautiful precision workmanship that went into making the lenses completely ruined. But I do take your point about useless lenses not being used. However, I still feel it's a lot easier to adapt the mount on an old plastic EOS camera using a Minolta rear lens cap than it is to convert the lenses.

My ultimate pipedream is digital film Smile but I'd settle for a universal film-to-digital conversion kit that fits any camera. All it would take is to replace the film pressure plate with a digital sensor. The circuitry, LCD, batteries and memory card etc would be in a separate module bolted underneath like a motor drive. I'm working on it! Smile


PostPosted: Sat May 15, 2010 2:09 pm    Post subject: Reply with quote
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.


In practice the monetary value of converted lenses does increase. For example, on eBay the converted 58mm f/1.2 Rokkors sell for (sometimes considerably) more than unconverted ones. This even if the conversion looks amateurish.

peterqd wrote:

But I do take your point about useless lenses not being used. However, I still feel it's a lot easier to adapt the mount on an old plastic EOS camera using a Minolta rear lens cap than it is to convert the lenses.


Well, 5D mk II owners might be a bit more hesitant to convert the mount on their camera, plus then it could no longer be used with modern lenses, etc. Of course, one might consider investing in a cheap used camera just to convert it, but in my opinion to go through the effort of converting a lens, the lens should be special enough that I wouldn't want to just use it on a secondary camera.

I guess it's the same argument that one could just get an old film body compatible with the lens and shoot with that. But most people will just end up not using the lens at all. (This does not necessarily include you or several other members of this group, but just look at flickr groups e.g. for the 58mm Rokkor f/1.2 and compare the number of conversion users to film users… And there must be far more unconverted lenses out there than converted ones.)

So, in practice, the conversion does ensure the continued use of the lens, and conversions have already increased the popularity of certain lenses greatly. Without conversion they would be sitting unused.


peterqd wrote:
Admittedly, as a craftsman, for me it goes against the grain to see all that beautiful precision workmanship that went into making the lenses completely ruined.


“Completely ruined” seems quite strong, considering that most conversions (even the destructive ones) only affect a very small part at the rear of the lens, and when mounted on a camera most amateurs would not even be able to tell the difference. The optics are the same, the focusing just as smooth, etc. Is the mount truly such a marvel of workmanship that replacing it with another piece of metal “completely ruins” the beauty of the lens?

Furthermore, many of these conversions are reversible (including my, admittedly amateurish, Rokkor 58mm f/1.2 using a drilled M42 adapter as the new mount). It's unlikely that most of them ever will be reversed, since the lenses offer more use and value in their converted state, but I don't think one can say that the lens is ruined if it can be restored to its original use.

And if we consider the conversion kits (which I personally don't use, preferring DIY hacks): why is the precision workmanship that goes into making those any less valuable or beautiful than what went into making the corresponding piece of the original lens? I would even argue that due to the additional constraints from having to fit the original design and keep the installation simple, it takes more effort to design and make these.


Also, what about lenses that have interchangeable mounts by design. The simple example would be Tamron Adaptall(-2)—if someone makes a Adaptall-2 to µ4/3 mount, does it ruin the beauty of the lens as it attaches this where a Tamron-made mount should go? What about lenses where the interchangeable mount is attached with screws and not strictly meant to be user-interchangeable (e.g. on certain lenses by Meyer, Steinheil, etc)?


PostPosted: Sat May 15, 2010 2:21 pm    Post subject: Reply with quote
Jim Buchanan over at FM Forum sells non destructive adapter. I got one from him for my second copy if the 1.2/58. He is very helpful at answering question regarding it.

I took the DIY route with M42->EF adapter with my first copy. It worked but it is irreversible job. If you don't appreciate mutilating lens, get it from Jim.

Disclaimer: I am not connected with Jim, just a happy customer passing along the information.


PostPosted: Sat May 15, 2010 3:35 pm    Post subject: Reply with quote
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.


PostPosted: Sat May 15, 2010 4:23 pm    Post subject: Reply with quote
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.

The market for these lenses today is fueled only by digital interest; otherwise the values as technological marvels only would be dirt low. We saw some of that a few years back when people weren't using them for digital.

I still contend that all lenses' value depends mostly on their usability. Virtually ALL lenses were made to support photography, and it is the photography that gives them purpose and value. Any lens I own only has value to me as a photographic tool. I have to remind myself of that every time I get drawn to interesting looking lenses; they are only to support my primary interest of photography, not to become the focus of the hobby.


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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