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Another Rokkor 58mm f/1.2 to Minolta AF conversion

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ocelli View Drop Down
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Post Options Post Options   Quote ocelli Quote  Post ReplyReply Direct Link To This Post Posted: 09 November 2007 at 20:06
I think it's possible.The difference in film to flange distance is only 1mm.
Minolta AF-44.5 Minolta MD-43.5

Even if it is possible, why bother?Modern lenses perform better especially with regard to resolution and flare.

Anyway for enjoyment purposes some lenses are worth converting especially the 58mm f1,2.

Edited by ruvmendis - 11 November 2007 at 13:26
 



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Magnus Wedberg View Drop Down
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Post Options Post Options   Quote Magnus Wedberg Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2007 at 20:19
Hijacking this thread a little. You owners, have you had "purple spot" reflection problems with your conversions?
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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: 09 December 2007 at 21:06
I haven't noticed any in mine.
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Magnus Wedberg View Drop Down
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Post Options Post Options   Quote Magnus Wedberg Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2007 at 22:04
OK! Which digital camera are you using it on?
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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: 10 December 2007 at 01:21
The A100.
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Post Options Post Options   Quote ABramley Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2007 at 01:34
I've also never noticed it on a 7D. I'm really tempted to try to rejig mine with AF confirmation... Wouldn't we also get accurate AS information then?
 



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Pete Ganzel View Drop Down
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Post Options Post Options   Quote Pete Ganzel Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2007 at 06:40
Hi Magnus:

Like the others, haven't seen this flare with any of the f/1.2 Rokkors I have (58mm Old, 58mm new style, 50mm MD). The torture test at f/8 revealed a nice contrasty image without a center spot;



This is identical on all the f/1.2 Rokkors all the way down to f/16.

On the other hand, at the same time I tested a 55mm f/1.4 Rikenon (M42) and the central flare is obvious from f/5.6 and getting worse to f/16.


Might be a problem with all f/1.4 lenses. Do you want me to check the Takumar I have?

Pete

Edited by Pete Ganzel - 10 December 2007 at 06:40
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Post Options Post Options   Quote Magnus Wedberg Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2007 at 13:12
Thanks all! Most interesting. Pete, actually there is a center flare in the 58 shot, but it's large and very faint, nothing else to expect and a great result -- much better than the AF 50/1.4 :-P No, I don't need anything else tested, I'm just curious, I might be in the market for a 58 to convert to AF mount... as well as possibly a 35/1.8.
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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: 10 December 2007 at 13:36
Originally posted by Turerkan Turerkan wrote:

<snip>you don't try to shoot macros at night anyway, do you?..


You betcha!
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ankit View Drop Down
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Post Options Post Options   Quote ankit Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2007 at 17:42
Great guide - thanks a lot to Arkku and Pete. I am tempted to try this myself. One question: from what I understand, the flange to film distance is 44.5mm for the AF mount, as opposed to 43.5 for the MD mount, and we are essentially moving the lens closer to the sensor when we adjust for infinity. Could this potentially interfere with the mirror assembly? I remember people shaving the mirror on their canon 5d to avoid this problem and was wondering if minolta (APS or full frame) would have the same problem?
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ocelli View Drop Down
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Post Options Post Options   Quote ocelli Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2007 at 17:55
Originally posted by ankit ankit wrote:

Great guide - thanks a lot to Arkku and Pete. I am tempted to try this myself. One question: from what I understand, the flange to film distance is 44.5mm for the AF mount, as opposed to 43.5 for the MD mount, and we are essentially moving the lens closer to the sensor when we adjust for infinity. Could this potentially interfere with the mirror assembly? I remember people shaving the mirror on their canon 5d to avoid this problem and was wondering if minolta (APS or full frame) would have the same problem?


No, I have used a rokkor 58mm with an A100.The 44mm Canon flange to film distance creates the problem.
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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: 10 December 2007 at 18:04
Originally posted by ankit ankit wrote:

One question: from what I understand, the flange to film distance is 44.5mm for the AF mount, as opposed to 43.5 for the MD mount, and we are essentially moving the lens closer to the sensor when we adjust for infinity.


I thought about this myself when I made the modification, but as I adjusted the infinity focus I went past the correct position once and could focus past infinity (i.e. the lens was closer to the sensor than it would ever really need to be), but still there wasn't a problem with the mirror clearance on my A100. It may have slightly more clearance than a full frame camera, though, but at the correct infinity setting there doesn't seem to be a problem on Minolta AF film camera either.
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Post Options Post Options   Quote bumblebee Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2008 at 18:23
Here is a very simple conversion of the 58mm 1:1,2.

I have attached a Minolta AF mount from a defect lens (Exakta 28-70 or Tok. 35-200, both fit). If you have luck, the screws fit without drilling. To align infinity focus I took the shims from the Tokina 35-200.
It takes about 30 minutes to change the mount and adjust focus.
Stopped down to f/5,6, the lens gets really sharp!
The best Bokeh is seen at f/2,8, not wide open.


A great piece of glass!

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ankit View Drop Down
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Post Options Post Options   Quote ankit Quote  Post ReplyReply Direct Link To This Post Posted: 08 January 2008 at 19:13
bumblebee, interesting. Can you give a little more details on how you got infinity focus? Did you replace the metal ring on the lens with the shims on the 35-200? Great pics, btw!
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