Another cult lens

[ChrisN]

Just for interest, the tube that forms the rf cam inside my 35 Summicron and my 50/2 Hex-M are both 32mm in diameter - presumably that is the standard diameter required to put the cam on the rf follower. The Pentax K 50/1.2 lens rear element is 35mm diameter. I think that might preclude it from this conversion, unless a stepped tube was fabricated, and then it might restrict the projected image circle. Does anyone know for sure?

 

[hans voralberg]

@Chris, the cam tube diameter on my Nikon 55/1.2 Amedeo converted lens is 33mm with the rear element recessed deep into the lens and it looks to be at least 35mm in diameter, so I don't think you will have problem with a stepped tube. And the image circle of a 50mm is most of the time a fair bit bigger than the film anyway. Best way to test is put a circular rim on the rear element and check the projected circle?

 

[varjag]

Roland, awesome job!

 

[hipsterdufus]

Very cool. It looks oddly appropriate on the Leica...

 

[ferider]

Just for interest, the tube that forms the rf cam inside my 35 Summicron and my 50/2 Hex-M are both 32mm in diameter - presumably that is the standard diameter required to put the cam on the rf follower. The Pentax K 50/1.2 lens rear element is 35mm diameter. I think that might preclude it from this conversion, unless a stepped tube was fabricated, and then it might restrict the projected image circle. Does anyone know for sure?

Chris, it varies, I measured before "committing" to the right size.

Above you can see on the left the size of the Pentax lens' rear element retaining ring. On the right side, you see the inside diameter of the Novoflex mount, and RF cam inside and outside diameter of my 50/1.4 v2 Summilux and 90/2 v3 Summicron.

The tube that I picked (inside diameter 1.311 ", outside diameter 1 3/8 ") falls well between Summilux and Summicron ranges.

One of the things I still have to see from the test film is if the cam causes vignetting. It shouldn't but I might have to cut it down at the corners.

Roland.

 

[raid]

Let us see what comes out. My 50/1.4 is patiently waiting in line ...

 

[batterytypehah!]

Sorry, I have to agree that this is interesting, but far from practical. Why not just buy a Pentax body? An ME Super goes for anywhere between free and maybe $100 in top condition.

Adapting the lens to an M-4P gives you a marginally lower top plate. Apart from that, the M body is bigger in the other two dimensions, much heavier, and requires an external meter.

No, sorry, I really don't get it.

 

[ferider]

You should look at it from the other side. The only technically comparable lens (min focus, speed, etc) for the Leica is the 50/1.4 pre-asph E46. Prices for that one are north of US 2000 these days.

How is your M3 coming along 🙂

 

[johannielscom]

hmmm...

does it have to be a 50? the idea of my rokkor 58/1.2 on my M2 is very enticing even without accurate framing.

Most of the time, RF lenses have an indexed cam to make sure the correct movement on the RF following wheel is retrieved from the lens movement.

SLR lenses do not have indexed movement, no need since you focus on the ground glass.

If you want to use an SLR lens on an RF you will need to find a lens that has lens movement as close as possible to the RF standard movement, which for a Leica translates to an 51.6mm lens. (Little secret: all Leica 50mm lenses are in fact 51.6mm)

When you find a lens for the 35mm format that comes close to the 51.6mm focal length, it's rear element movement will likely be identical to the movement the RF following wheel needs.

You could adapt that 58mm to Leica M, but the lens movement will not correspond to the RF following wheel movement. As a result, you will either have to zone focus and ignore the RF patch, or use the RF patch and have misfocused shots...

Which is a shame, I also would love to convert a 58mm lens: my Nikkor-S 58/1.4...

 

[raid]

I would love to convert the Zeiss 50mm 1.4 HFT (for the Rolleiflex 35mm system) to M mount. Amedeo offered once such a conversion.

 

[Gabriel M.A.]

Awesome. I own this lens also, but I'm a complete maroon when it comes to doing something like this.

Yet if roland either does this for a fee or sells the needed part w/instructions, I'd of course get in line.

 

[MikeL]

Yet if roland either does this for a fee or sells the needed part w/instructions, I'd of course get in line.

Just don't buy the first version. Wait till the second comes out since all the kinks will be worked out. (I read that on the internets, and just repeat what I read since it sounds like wisdom to someone lacking it)

Nice mod ferider! And I like how you've set the expectation with D. that logically, you have to have a second body with each system. Gonna start working on that with the boss lady.

 

[batterytypehah!]

You should look at it from the other side. The only technically comparable lens (min focus, speed, etc) for the Leica is the 50/1.4 pre-asph E46. Prices for that one are north of US 2000 these days.

How is your M3 coming along 🙂

Hmm. For the price of even the cheap adapter, you can easily find a good Pentax SLR body. Two if you go for a Ricoh, although admittedly they are bigger. Nope, still not logical to me.

Alas, the M3 project is on hold until I can raise some cash for parts.

 

[d_c]

Surely any lens could be coupled to the rangefinder, not just one with a focal length of 51.6mm. It should simply be a case of establishing the correct curve / slope to cut the cam bearing surface to - okay maybe not so simple but achievable.

Assuming the flat profile works for the OP's lens, it may be that the Leica M rangefinder uses a lens of approx 50mm as the basis for its rangefinder action. Because there is a fixed ratio based upon the focal length linking the extension of a lens to the point that it is focussed on this should mean that you would be able to do the same with any 50mm lens provided the space exists at the back of the lens to install a cam surface as the OP has done.

 

[Nugard]

So much words... Show us some photos from the m camera with the lens...

 

[batterytypehah!]

By the way, before anybody gets this wrong: Of course simply wanting to do this is a perfectly good reason in itself. It's an interesting challenge and it looks like the OP did a great job. I just wanted to point out that it's a bit of a solution in search of a problem 😉

 

[raid]

Awesome. I own this lens also, but I'm a complete maroon when it comes to doing something like this.

Yet if roland either does this for a fee or sells the needed part w/instructions, I'd of course get in line.

Gabriel: You are Nr. 2 in line.
Let's all line up here.

😎

 

[hans voralberg]

How do you calculate nominal focal length? I'd like to try with my Zuiko glass!

 

[Phil_F_NM]

Surely any lens could be coupled to the rangefinder, not just one with a focal length of 51.6mm. It should simply be a case of establishing the correct curve / slope to cut the cam bearing surface to - okay maybe not so simple but achievable.

If the focal length is more than ~.5mm away from 51.6mm this will only work if the lens rotates when focusing. This is where the moving cam with an angle ground into it comes into play. It's how all LTM wides focus to transfer the motion of a 51.6mm lens to the Leica body cam follower. Most SLR lens rear elements do not rotate and so this won't work for focal lengths different than ~51.6mm.

By the way, I checked the specs on the Zeiss 50mm lenses for the old Contax SLR's since I have those too and the nominal focal length for the 50mm f/1.4 is 51.8, the f/1.7 is 51.9 so conceivably they could be converted too.
EDIT- I misread the nominal focal length of Leica (I had 51.8 stuck in my brain for some reason) so I doubt the Zeiss lenses will work.

The Zeiss lens with a 51.9mm nominal focal length will work fine. All Dual Range Summicrons were made in a nominal focal length of 51.9mm and the focusing cam for both near and far ranges is ground flat, no angle.

Phil Forrest

 

[ferider]

Testfilm results

Testfilm results

Some boring test shots ....

But: she is alive and kicking 🙂

1m focus distance (using camera RF):

30m focus distance (using camera RF):

Infinity:

Focus accuracy is better than expected. No vignetting either 🙂

To be followed with "real" stuff on the week-end.

Roland.