Review: ferider modified Pentax 50/1.4 in M-mount adapter

[Jamie Pillers]

So now we have to try to talk Roland into inventing a modification of the rangefinder mechanism itself! 🙂

 

[paulfish4570]

jamie, thanks for the landscape compliment.

 

[raid]

So it must be the K mount version of the 50/1.4 and not the M42 version, correct? The M42-K adapter would not work here.

Maybe this was explained somewhere.

 

[paulfish4570]

correct you are ...

 

[charjohncarter]

Cool, so Roland created the ability for the rangefinder to work with the lens?

 

[paulfish4570]

yeppie. he sure did. he showed the first he did in the thread whose link i posted in the thread starter ...

 

[charjohncarter]

thanks.....................

 

[ferider]

Thanks for the review, Paul, and also for posting pictures of the lens on the Bessa - they make a great pair together. And like Jamie, I'm a fan of your B+W landscapes ....

The image quality is awesome. Makes me think of 50/1.4 Summilux quality. Great review, thank you Paul and Roland.

Thanks, Mablo. And I agree with you - I've shot my pre-asph v2 next to the Pentax lens and the images look very similar. Not surprising, since the optical designs are closely related. Even better, the Pentax lens distorts a little less, and has a minimum focus of 0.7m; on the other hand, the Summilux is more compact which is why I'm keeping it.

Roland... VERY cool modification - thanks for trying it! Just to be clear: the modification is essentially adding the focusing 'cam' to the slr lens so that it pushes the rangefinder wheel in the camera... correct? And can I assume that its not a minor exercise to calculate the dimensions of the cam.. correct? And regarding focus distance: the pentax lens normally has a close-focusing distance of something less than a half a meter. Can the Leica M rangefinder mechanism accomodate this shorter distance, or is the modification limited to 0.7m?

Hi Jamie: the cam is made from a brass pipe by hand, with saw and file. Only in the end is accuracy needed, when I grind it with a stone to match infinity on my reference camera, an M3.

The Pentax SMC lens is a "lucky coincidence", since it's focal length matches the Leica RF standard of 51.6mm. This, I measured before I modified my first copy (a donation from a friend). It guarantees that focus is right at both close focus and infinity. When the lens focuses closer than the camera's minimum focus (0.7m), the RF cam simply decouples.

Enjoy your lens Paul. BTW, it also has a tag in the flickr Leica M forum 🙂

Best,

Roland.

 

[jsrockit]

Thanks for posting these images. I remember the original thread, and was intrigued. It looks like a relatively simple project. The resulting lens looks like it is not oversized, and well suited to an M mount camera. It seems really usable.
How accurate is the focussing?

Christian, thinking about doing this? I have a 50mm f/2 Pentax you can experiment with... 😀

 

[Griffin]

Is the lens still usable on a Pentax body after the mod? This is one if my favorite lenses. It's never off my MX.

 

[ferider]

Is the lens still usable on a Pentax body after the mod? This is one if my favorite lenses. It's never off my MX.

No, it's not, Griffin. The RF cam is glued to the ring holding the rear element. Like this:

Roland.

 

[Particular]

Christian, thinking about doing this? I have a 50mm f/2 Pentax you can experiment with... 😀

Perhaps, but it is low on my project list. I'm not sure that is the right lens though. Do you even have an M body nowadays?

 

[semilog]

The RF cam is glued to the ring holding the rear element. Like this:

Why is the RF cam cut away rather than fully cylindrical as on a native Leica lens?

 

[ferider]

Why is the RF cam cut away rather than fully cylindrical as on a native Leica lens?

It's not cylindrical on all Leica lenses (for example the 90/2 v1).

In any case, I cut it to have less work grinding and avoid vignetting (shouldn't be a problem when comparing to my v2 Summilux but just in case).

Roland.

 

[semilog]

Helpful answer. Thanks.

 

[varjag]

Nice work Roland!