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11-18-2010, 01:13 PM   #1
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Old (new to me lenses) Rokkor 50 and 58 1.4

I just picked up a couple of lenses I have been eyeing for a bit.

The 50mm is a MD Rokkor-X 50mm 1.4 and the 58mm is a MC Rokkor-PF.

The 50mm is in excellent condition while the 58mm has definitely seen a lot of use. The glass is in great condition so it really doesn't matter.

The total price for both was $55+ tax from a local camera shop.

Now i just have to wait for those M42 to K-mount adapters to arrive from China so I can convert these lenses to K-mount.

Of course the dream lense I want to get is the Rokkor PG 58mm 1.2.... hehe.

How is the Rokkor 50mm lens compared to a takumar or pentax smc or non-smc 50mm 1.4?

11-18-2010, 02:14 PM   #2
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Minolta Rokkor lenses were wonderful lenses, but I have no idea how they behave with adapters to Pentax K as far as infinity focus goes. But their
lenses from the early 70s compare favorably to Takumars.

It's good stuff.
11-18-2010, 02:19 PM   #3
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I have that Rokkor 1.4 up in the attic with a few others. It was great, then. Don't know now.

How specifically are you converting it to K-mount? I haven't seen a Minolta-to-M42 conversion ring around.


Thanks,

M
11-18-2010, 03:58 PM   #4
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QuoteOriginally posted by Ira Quote
Minolta Rokkor lenses were wonderful lenses, but I have no idea how they behave with adapters to Pentax K as far as infinity focus goes. But their
lenses from the early 70s compare favorably to Takumars.

It's good stuff.
I'm not adapting them... I am converting them. An adapter from Minolta to Pentax would have to have optics which would make adapting them pointless.

QuoteOriginally posted by Miguel Quote
I have that Rokkor 1.4 up in the attic with a few others. It was great, then. Don't know now.

How specifically are you converting it to K-mount? I haven't seen a Minolta-to-M42 conversion ring around.


Thanks,

M
With help from these posts/pages.

The last link is probably the most helpful as the guy there uses M42 adapters as the new mounts.

https://www.pentaxforums.com/forums/pentax-lens-articles/56234-konica-minolta...ld-lenses.html

Minolta MC Rokkor 58mm f/1.2 mount conversion, part 1/5 | Flickr - Photo Sharing!

How to Convert Your Minolta MC Rokkor 58mm f1.2 Lens to Canon EOS Mount

11-18-2010, 04:00 PM   #5
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I started out with Minoltal-Rokkor I have to say that on film they are still my favorite. Espescially the 58/1.2 . However I haven't found a way to convert them for use with pentax K. I believe the register distance is quite a bi closer on the rokkors. Unless you can remove some of the rear of the lens then attach the m-42 adapter to the back. Otherwise no focus to infinity.

Eric
11-18-2010, 04:07 PM   #6
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QuoteOriginally posted by erkie Quote
I started out with Minoltal-Rokkor I have to say that on film they are still my favorite. Espescially the 58/1.2 . However I haven't found a way to convert them for use with pentax K. I believe the register distance is quite a bi closer on the rokkors. Unless you can remove some of the rear of the lens then attach the m-42 adapter to the back. Otherwise no focus to infinity.

Eric
Take a look at the last link in my post.
11-18-2010, 06:24 PM   #7
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QuoteOriginally posted by cyclone3d Quote
Take a look at the last link in my post.
Thanks for the link ! I have a few I might have a go at. Just not the 58/1.2 or 85/1.7 I scrimped and saved too much 30 years ago for that.

Let us know how you do ! It's much apreciated.

Eric
11-19-2010, 07:40 AM   #8
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I just took at look at the back of both lenses this morning. The 50 is going to be a bit more challenging to convert than the 58 is.

On the 50, the aperature linkage is mounted on the lens mount so I will have to swap it over to the k-mount which should be "fun".

Trimming aprox. 4mm is not going to be nearly as easy either as there is not spacer on the 50. I will probably have to trim down multiple parts to get the 4mm required for infinity focus.

I'll post project pics/instructions for both once I get the mounts and start the conversion.

11-19-2010, 10:56 PM   #9
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Getting impatient for these adapters to arrive.... and it will probably be at least another week before they are here.

I decided to do some preliminary testing with the 58 to see how much of the spacer would have to be removed.

I measured it, and it looked like the whole spacer would have to go so I did some hand-held tests with my camera, and it really does look like the spacer is going to be left out. Depending on how the m42 adapter sits, I may have to trim even a little more to get proper infinity focus.

The mirror will have no interference problems with the lens even with removing that much thickness from the lens... which is a very good thing.

Another good point is that it really shouldn't be very difficult at all to make it so I can use stop-down metering.
11-24-2010, 10:03 AM   #10
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The 58mm conversion is going to take a little more work that I originally thought.

Even with the infinity adjustment ring set at the minimum AND the spacer removed, not only is it still not quite getting infinity focus, the mirror is tagging the edge of the rear lens assembly so I am going to have to file that down as well.

IF the m42 to k adapter gets the lens a bit closer to the body than using a k mount from a scrap lens it should take care of the infinity focus. If not, I may have to trim down the lens body where the camera mount goes, which would also mean I would need to trim the aperature ring as well.
11-24-2010, 12:51 PM   #11
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The adapters arrived in the mail today. The good news is that the flange is only about 1/3 as thick as the regular k-mount flange that I was testing with.

This should hopefully take care of or get me really close to infinity focus.

The only thing I really have to do to make this work is to come up with something that will hold the aperature ring in place since the spacer is what was holding it in place originally. I have a couple ideas already so I'll have to try things and see what works best.

And I'll also have to come up with an extension for the aperature linkage if I want to use stop down metering.
11-25-2010, 12:43 PM   #12
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I got the m42 adapter setup as a mount this morning.

the bad thing is that the camera mirror is hitting the back of the lens now and it looks like I may have to trim the mirror since I have already taken as much material as possible off of the rear element housing.

If I take any more off, I am afraid that there will not be enough left of the screw in ring left to hold in the rear element.

Before I trim the mirror, I am going to finish assembling the lens and see if I have infinity focus where the mirror still clears the rear element housing.... I really doubt it will, but it will probably be pretty close.
11-25-2010, 08:12 PM   #13
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Measure twice cut once ! Now trimming the mirror on my camera is where I would draw the line. And I work with glass every day Good luck ! And watch out for thos little shards of glass, They Hurt !

Eric
11-26-2010, 06:30 AM   #14
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QuoteOriginally posted by erkie Quote
Measure twice cut once ! Now trimming the mirror on my camera is where I would draw the line. And I work with glass every day Good luck ! And watch out for thos little shards of glass, They Hurt !

Eric
I think it may actually have infinity focus without having to trim the mirror. I will do some more testing later in the day and post results.
11-26-2010, 08:27 AM   #15
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Wow ! That is some hardcore work, like it ! Post some pics of your project, it looks awesome.
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