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Another Rokkor 58mm f/1.2 to Minolta AF conversion

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Arkku View Drop Down
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Post Options Post Options   Quote Arkku Quote  Post ReplyReply Direct Link To This Post Topic: Another Rokkor 58mm f/1.2 to Minolta AF conversion
    Posted: 29 August 2007 at 15:51
Hi,

I recently acquired an old Minolta MC -mount Rokkor 58mm f/1.2 lens (got a good price because it had stuck aperture blades, which was easy enough to repair with a bit of cleaning). Inspired by Pete Ganzel's modification of the lens, I decided to try and convert it to the Minolta AF mount.



As I don't have the opportunity to machine any new parts for the lens, I opted to substitute an M42 to Minolta AF adapter for the MC lens mount, getting the AF mount from the adapter. This required only the drilling of some holes in the adapter and sanding down a ridge on a spacer ring on the lens (with only a tiny cosmetic impact if the modification is ever reversed). From receiving the lens in the mail, planning and executing the basic modification only took about 45 minutes, so it's definitely not a hard one to do, and gives access to a very nice old lens on Minolta AF cameras, without resorting to image-degrading adapters.

The fiddly part, taking maybe two and a half hours, was readjusting infinity focus on the lens, so that the distance scale and infinity position coincide exactly on the new mount. This step requires a bit more disassembly of the lens and lots of trial and error in finding the position, but in the end the result is perfect, with spot-on infinity focus and alignment of the distance scale, as well as the lens locator dot. The project requires only an inexpensive, expendable M42 adapter as parts other than the lens.

Here's the new mount on the lens, with a link to a series of photos and a guide to making the modification in my flickr stream:



Edited by Arkku - 29 August 2007 at 16:10
 



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Bob J View Drop Down
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 16:11
Looks like a great guide - thanks for posting!
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dogears View Drop Down
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Post Options Post Options   Quote dogears Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 16:31
Wow! and congrats! Wish I had the means to do the same... but first I gotta find that lens :))
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Post Options Post Options   Quote ricardovaste Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 16:57
Wow thats some awesome portrait lens youve got there now!
Id like to try this one day. But id probably just buy a kit off peter, so save any mistakes.
Though, when i was fixing my macro lens, and the metal mount of it was off. I fiddled with it and a (old/scratced/useless) minolta SR fit 28-70mm lens and managed to fit them together, by simply screwin it in! And infinity focus was there and all. Strange, didnt think it was that simple.
Id sure like to have a 58mm f/1.2 and a 24mm f/2.8 on my A-mount system =].
Congratulations btw!
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Anssisa View Drop Down
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Post Options Post Options   Quote Anssisa Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 17:11
That looks nice, would be nice to try that one som time. Maybe some day at a Finnish Dyxum meet..

Do post pictures taken with it also.
"Click,Click,ClickClickClick" By: A700 + | S 50 f/1.4 | M 85 f/1.4 G (D) | S 135 f/2.8 STF | M 80-200 f/2.8 APO HS G |
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Dumont View Drop Down
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Post Options Post Options   Quote Dumont Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 17:13
Very nice. I would like to see some photos too, especially taken wide open at f1.2
 



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ricardovaste View Drop Down
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Post Options Post Options   Quote ricardovaste Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 17:32
Yes, forgot to ask that! Would love to see some photos posted, especially wide open also, and f/3.5 =]
WEDDINGS: Richard Harris Photography | PERSONAL WORK: ourfragments.com
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Arkku View Drop Down
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Post Options Post Options   Quote Arkku Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 21:17
So far I have only taken a few shots with this lens, so I don't have much to post yet. I'll certainly play around with it come daylight again, etc, but so far here's one at f/1.2:



Note that it's also at ISO 400 and handheld 1/13 s, so it may not be the best example. I like the smooth bokeh, though.


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Sanjuro View Drop Down
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Post Options Post Options   Quote Sanjuro Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2007 at 22:27
Really nice Arkku, great guide. Now I need to find one of those lens.
A 1.2 would be great for the winter here.
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Sanjuro

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carpents View Drop Down
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Post Options Post Options   Quote carpents Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2007 at 05:21
Thanks for the instructions. I'm pretty confident that adjusting the infinity focus like this will allow me to use one of these on my Pentax. Normally I wouldn't be able to use it to infinity because the Pentax mount is deeper than the Minolta (both manual and AF) mount, but if I can change the focus point it should work.
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Post Options Post Options   Quote Dumont Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2007 at 06:26
That sample is nice, great job adapting the lens. I used several MD/MC mount lenses on my 5D but with the adapter with glass the lens could not be used wide open, the subject would "glow" no matter what shutter speed. I have since sold them all and stuck with AF or the occasional M42 lens.
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nazzza View Drop Down
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Post Options Post Options   Quote nazzza Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2007 at 14:28
I've recently bought a 58mm 1.2,
do you think that if I'll use an m42 with focus confirmation (like that of haoda) to convert this lens to minolta AF mount, I'll have focus confirmation working?
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Post Options Post Options   Quote georgiaboy Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2007 at 14:37
Yes you will.
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beline View Drop Down
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Post Options Post Options   Quote beline Quote  Post ReplyReply Direct Link To This Post Posted: 20 October 2007 at 03:08
Here's a question, with a lens like this set up like this, is it possible to have the camera automatically stop down the lens? I understand you have to set the aperture manually. And do stop down metering.... But I never understood how it works from there...
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