Manual Focus Forum

Nice. I love my 1.7 Planar.

Wow.. Sounds a great idea I would love to try it. Anybody let me have an old Contax lens very cheap !!!

Rob Leslie wrote:

Wow.. Sounds a great idea I would love to try it. Anybody let me have an old Contax lens very cheap !!!

FWIW, you can probably pick up a Yashica ML 50/2 for under 5 pounds if you look. These share the Contax mount.

I was really inspired by this idea and tried to figure it out on my own. My approach is slightly different. First, I just check the register distance of Pentax K and C/Y. They are very close to each other 45.46mm vs. 45.5mm. So why don't we just fit the K mount into C/Y lens? And see how they work. What I found out: It works great!!!

The way I did was: I just took the C/Y mount out of my Yashica 50mm 1.4 and 28mm 2.8 then replaced them by the P/K mount from Pentax-M 50mm 2.0. Amazingly, they fit exactly and everything aligns as the original lens. I shot some pictures to check for infinity focus and fine, no problem.

Let's try it guys and see it by yourself. Enjoy

http://forum.contax-club.org/viewtopic.php?t=12815

Excellent discussion how to modify the mount on the camera to accept PK and C/Y lenses.

xtriky wrote:

I was really inspired by this idea and tried to figure it out on my own. My approach is slightly different. First, I just check the register distance of Pentax K and C/Y. They are very close to each other 45.46mm vs. 45.5mm. So why don't we just fit the K mount into C/Y lens? And see how they work. What I found out: It works great!!!

The way I did was: I just took the C/Y mount out of my Yashica 50mm 1.4 and 28mm 2.8 then replaced them by the P/K mount from Pentax-M 50mm 2.0. Amazingly, they fit exactly and everything aligns as the original lens. I shot some pictures to check for infinity focus and fine, no problem.

Let's try it guys and see it by yourself. Enjoy

Wow!

Very cool!

Thank you very much for the very helpful links from you guys. The approach of modifying camera mount to accept C/Y lens is very smart. However, it requires some sort of more mechanical skills than mine. In addition, there is no permanent modification in either camera or lens mount in my method. It is totally reversible because actually, I just swap the P/K and C/Y mounts.

This is the outline of my experiment:

1. Unscrew the P/K mount from a Pentax-M 50mm 2.0 or other P/K lenses


2. Take out the black plastic inner ring and keep only the outer shiny metal ring


3. Strip off the C/Y mount of the Yashica lens

The Yashica ML 28mm 2.8 lens


With C/Y mount:


Without C/Y mount:


4. Screw the P/K mount flange into the C/Y lens. Note: only one (1) screw (that is opposite to the red dot on the P/K mount) can be screwed in. However, I think it is enough to "super-glue" the P/K mount and the C/Y lens together (as good as 4-5 screws)

Hybrid model: P/K mount on C/Y lens


Everything aligns: The red dot on the P/K lens match the exact location of the red aperture indication mark on the C/Y lens. Thus, the C/Y lens will be mounted at the correct 12 o'clock position and locked in place just like any other P/K lenses.


Infinity focust test:
I did not make any adjustment to obtain infinity focus, it is just natural. I think the reason is the very small difference between register distance of the two lens mount systems.

This is my test shot for infinity focus (maybe @2.8)

Full frame:


100% crop at center:


10% crop at corner:


If you want to be safe, just try out my instruction. I hope it will help. Thanks

This is interesting indeed. Thanks for posting your images magicmud and xtriky.


magicmud.

Great shots! Did you just loosen the three small screws holding the bayonet and then shimmed the whole bayonet to the right "height" to fit the K mount?




strixy.

I see you used a Yashica ML lens. I have three nice C/Y Zeiss lenses, but the Zeiss brand lenses looks a bit different as the flange doesn´t have the attaching screws at the outer part of the flange, but ON the bayonet itself.  This to make the bayonet parts replacable, I assume.

Have you tried the same surgery with a Zeiss lens?  Or anyone else here, for that matter? Or maybe the pbase/wong lens IS a Zeiss?

Thank you.

// Mats

Last edited by matsoberg (2007-10-05 17:23:43)

Magic.

I´m looking forward to your report with great hope! :-)

Here´s the pbase link again (but I assume you´ve looked it over quite some times);
http://www.pbase.com/wesleywong/diy__co … _m42_mount

Would this one be a Contax Zeiss lens you think? I don´t really recognize the parts in full here, and the aperture ring doesn´t have the same knurling as mine AE version lenses.

Thanks,

// Mats

yeah, it took me a bit of work to get the screws of (they have lacquer on them) so you need to put a lot of directed force on them (i had to have a friend help with a pair of pliers to turn the screwdriver as i held the lens and pressed down on the screwdriver so it wouldn't slip and strip the head of the screw). Also give a the screws a bit of a tap with a hammer and screwdriver to crack some of the lacquer.
Mats, i don't think that its a Contax Zeiss lens in that conversion since like you mentioned it, the aperture ring isn't the same and I think the mechanism for how the aperture ring holds the correct position is different, with the planar 1.7 its a ball and spring that "clicks" into place along a metal ring underneath the mounting plate.

Hi,
I am interested in this C/Y to PK lens mount conversion. Will any Pentax K mount do or does it have to be the Pentax-M lens?

Thanks,
Simon

Hi xtriky,

Yes that is helpful. I have a Yashica ML 50mm f1.4. Unfortunately, the previous owner had the lens mount modified by machining off the three lugs leaving just the circular lens mount to fit a Konica bellow. I then bought a Yashica ML 50mm f1.9 in the hope that I can simply swap the lens mount over. It was both a waste of time and money. So now I can rescue this lens by buying a Pentax-M lens thanks to you and magicmud.

I hope to use it with my Olympus E-300 with a PK adapter.

Regards,
Simon