C/Y Planar 50 disassembly and conversion

[the_Suede]

Hi all!

I have now successfully converted a couple of lenses to Nikon by replacing the entire rear mount with a new base plate that started life as an M42/Nikon adapter - a few Oly's (easy), one Leica R (even easier!) and two Contax 50's...
My question is: Has anyone here ever gone at the apertureblades of a C/Y planar 50? I can't seem to find any references at all on the net, and I'm hesitant to accidentally break something... Without a mechanical drawing, I don't know if any of the lenses will come loose if I go at it from the front, and from the back it seems entirely impossible. I don't want to disturb the mountings to much, the lens is perfectly centered as it is. Any experience at all with dismantling a planar 50 is appreciated!

The front group SEEMS to be mounted in a one piece mounting barrel, but even with moderate force applied, it won't budge.

Anyone?

[the_Suede]

Just thought I should add a few pics of the baby, the conversion is done - and works perfectly.

I've rerouted the aperture-spring:


with a piece of a Pilot ballpoint cap, the clip, as a new seat


I've reused a part of the original mounting shim to retain the "clicks" in the aperture setting (and I've added a few half-stops as well). Here it is, superglued to the adapter:


After a few turns on a lathe, the former M42 adapter fits like a glove:


And here's the first live shooting victim, caught trespassing in my back yard

[poilu]

welcome
superb job and impressing result

[Jesito]

Wow, that's a great job!
I didn't dare to do the conversion to M42, I had the lens disassembled but at the end I run into doubts....
Congratulations, you are a braver man than me

Jes.

[sichko]

A nice piece of work.

[the_Suede]

Well, thank you for the encouragement, everyone...!

The reason for my question is that as I now have two (soon to be three) C/Y 50's, so I thought to convert one of the samples into a "soft defocus" F/2.2 lens by inserting a "star" shaped light blocker just in front of the aperture mechanism. The light-blocker would look like this:



This will cut the amount of light added from F/2.8 to F/1.7 in about half, and hopefully it will take away some of the bright outlines in the back defocus lines/highlights. The other option is to try to "soot" the outer rim of the lens-surface closest to the aperture, but I have doubts if I can do this evenly all around.
But first I have to get at the aperture mechanism... I love the sharpness and contrast in this lens, but in some cases the bokeh is a little to "busy", even showing some double lining:


But in easier cases, it can be just sublime... This crop is almost 100% size:


And some results are somewhere "in between":


As I have confidence in the main principle and access to the tools and spare lenses I would really like to try this. But then I have to know how to dismount the front lensgroup without disturbing anything... As I said earlier, all experience is appreciated!

[the_Suede]

The "Blue Pill" stuff is a movie quote from the Matrix... Neo - a character in the movie - is forced to make the informed choice: Keep your view of the world, what you THINK is reality, or be exposed to the the real truth...
I guess this means that you have realize that your own personal opinions and views do not always reflect what the true reality is. This distinction is not always as easy as you think... We tend to favor the way we SEE things over the way they really are.

This is just some food for thought.

[Flor27]

Hello,

[the_Suede]

I work in the printing industry, mainly with high volume printing, and through this I know some persons who work for a plastic precision part manufacturing plant here locally. The part will be cut from 0.8mm stabilized black Styrofoam or 1mm PStyrene with the aid of a NC high-pressure waterbeam cutter... I've mailed him a .dxf Autocad file, so the part(s) will be cut the same day that I know the three right right diameters. He'll scale my sketch accordingly and just send the drawing to the cutter.

I also have this Pentacon, albeit the "Pentacon Electric 135/2.8" model Is this the same optically? It's on my "on hold" list for conversions as the main helicoid isn't deep enough to properly meet infinity focus on a F-mount camera... At least not without some serious work on the lathe.

I would really like to try this on a Nikkor 135/1.8, I'm pretty confident in handling the old AIS lenses by now - I've dismounted quite a few.... (And totally bummed a few in the beginning also, I have to admit)

[Flor27]

That's great to have access to such tools for this kind of project

All the Pentacon and Orestor 135/2.8 are sharing the same optical layout and the aperture is easily reachable on 6 iris blades copies as the barrel that hold front elements car be unscrewed in one piece :
http://forum.mflenses.com/pentacon-auto-2-8-135-partial-disassembly-and-cleaning-t9836.html#82213

It seems to be as easy as it on older non auto models :

http://www.mqcvisions.net/Pentacon_135_2_8/Pentacon_5.html

I have also plenty lenses for such project : Yashica ML 50/1.7, Mamiya 55/1.4, Pentacon 50/1.8, and maybe just for fun a dirty Rokkor-PG 58/1.2

[the_Suede]

Thank you very much for the links, they were indeed helpful... Always nice to be certain. I have the Pentacon 50/1.8 from the same series, but there seems to be to much work involved in correcting the 50mm for Nikon F flange distance (46.5mm)... I had the ML50/1.7, sold it for the same reasons :/
I've heard great things about the Mamiya 55, in your shoes that would be my priority! And of course the mighty Rokkor... I want one of those!

But still noone that knows about the Contax 50/1.7...

[the_Suede]

Answering my own question here... - Yes the entire front group of an C/Y 50/1.7 can be dismounted a one piece. In fact it's only press-mounted into the central barrel of the lens. The trick is in getting it to move out the first mm so you get a grip on it. So, now were on to the next step!

[LucisPictor]

Wow! I am deeply impressed by your talent.
Good to have another lens-whiz (apart from Peter, Andy and Jes just mention these three) onboard.