Trying to get my Leica M lens to work on DSMC2 gemini

[harjotsingh]

Hey Guys, ive been reading up on getting these lenses to work on red cameras and ive gotten a bit confused. The Red mount seems to say you cant use lens wider than a 50mm. I also heard you need a thinner oplf from leitz cine? does anyone have experience with this?

 

[Les Hillis]

There are basically two issues using Leica-M mount lenses on RED cameras.

First is getting the lens to physically fit onto the camera.

The second is the optical performance of the Leica-M lens and RED sensor combination even if you can get the lens to fit into the lens mount.

The RED OLPF plays a part in both of these issues.

The problem with the Leica-M lenses is how close their very short flange focal distance makes them sit to the sensor. Which means if the lens has a rear element that protrudes out past the back of the lenses bayonet mount (the chrome part at the back of the lens body), it will push up against the OLPF frame and you won't be able to attach it to the camera's Leica-M lens mount.

All the interchangeable DSMC1 OLPF's accomodated the protruding rear lens elements to some extent by having a rounded recess in the OLPF frame that the rear lens element could fit into, as seen here - https://www.bhphotovideo.com/c/prod...11_440_optical_low_pass_filter_for.html/specs

There were still Leica-M mount lenses with longer protruding rear lens elenents that wouldn't fit though, and there were some that would fit but which had limited focusing ability, as the rear lens element would extend and retract as the focus changed (extending for closer focusing, and retracting towards infinity).

In addition to that, I believe the specific Leitz Cine Leica-M OLPF was optically different in some way than the other RED DSMC1 OLPF's, in order to improve the optical performance of the Leica-M lens/RED sensor combination, but I never tested it out myself.

Which gets to the point that even if you could get the Leica-M lenses onto the RED camera, there could be significant visible colour-shifting and blurring of the edges of the frame, as the RED camera sensors simply weren't designed to capture light rays coming in from the steep angles the lenses would project. I've heard the actual Leica-M stills cameras were designed to accommodate this to some extent, but even then I've seen some Leica-M mount lenses showing visible vignetting and blurring even on Leica-M camera's.

And so that's basically where the 50mm focal length limit came in, as most Leica-M mount lenses 50mm and up don't have protruding rear lens elements, so they can actually fit on the camera, and they aren't so wide angled as to produce vignetting and other anomalies on the edges of frame.

With DSMC2 though, the general OLPF design changed and the rounded recess was removed, I believe to facilitate better flare guarding, as can be seen here - https://www.bhphotovideo.com/c/prod...ital_cinema_790_0513_dsmc2_standard_olpf.html

With this OLPF, the range of Leica-M mount lenses that would fit on the RED camera's was reduced. Whereas there were some lenses with slightly protruding rear lens elements that could fit with the general DSMC1 OLPF's, now the Leica-M mount lenses bayonet mount at the back of the lens was sitting flush with the frame of new DSMC2 OLPF.

But at the same time, the new Leitz Cine DSMC2 Leica-M version of the OLPF kept the rounded recess and increased the overall size of the OLPF glass out to the same width and height as the new VistaVision-sized OLPF's designed for the DSMC2 VV sized sensors, as can be seen here (the Leica-M version) - https://www.bhphotovideo.com/c/product/1456026-REG/leica_11_441_optical_low_pass_filter_for.html and here (the standard VV version) - https://www.bhphotovideo.com/c/prod...l_cinema_790_0558_dsmc2_vv_standard_olpf.html

So that's where you're at with DSMC2. With the RED DSMC2 OLPF's, you can only use Leica-M mount lenses that have rear lens elements that don't protrude at all past the chrome bayonet part of the lens body. Or you can use the Leitz Cine Leica-M DSMC2 OLPF's that allow for the use of some (usually wider than 50mm) lenses with rear lens elements protruding (to some extent anyway), at the risk of decreased optical performance at the edges of frame.

With DSMC3 the user interchangeable OLPF's were gone and the RF mount was introduced, which has a flange focal distance of 20mm, compared to the 27.8mm of the Leica-M mount. What that actually means in terms of Leica-M mount lenses fitting, or their optical performance with the DSMC3 sensors, I don't know. I imagine they'd look pretty good, but I haven't tested it myself.

Didn't mean to write so much. Last thing I'll say is, even with the standard RED DSMC1&2 OLPF's, there are definitely some Leica-M mount lenses that look amazing on the DSMC1&2 camera's. But at the same time, it would also definitely be easier and less of a hassle to just avoid the whole thing and go with PL or EF lenses.

 

[harjotsingh]

Thanks for the indepth information! i wish this community allowed to give points for people who reply with so much detail

 

[Les Hillis]

No worries, glad to help out when I can.

 

[Karim D. Ghantous]

I presume that M lenses work better in S35 mode?

 

[Les Hillis]

I presume that M lenses work better in S35 mode?

Most, if not all, Leica-M mount lenses are designed for Full Frame 35mm Stills cameras.

So yeah, using the lenses on a camera that is either at, or can crop into, the smaller S35-sized frame (like all the RED cameras do/can), will cut out some of the edges of the lenses image circle where the aberrations can occur (due to the sensors of the RED cameras not being designed to capture the light from the lens like Full Frame 35mm physical film is).

But even so, going wider than the 50mm focal-length recommendation on a RED S35mm-sized sensor, might still require cropping even further into the S35 format size to get rid of the vignetting, smearing and discolouration around the edges of the frame. There's a 24mm Leica-M lens that would fit the DSMC1 cameras for example. With that amount of cropping though, you lose so much field of view (and resolution) you may as well be using a 50mm lens (without cropping) anyway (exluding the possible practical or creative reasons why you might want to do it).

Again though, on the optical side of it, I never did try the Leitz Leica-M OLPF's, so maybe there was something to them that improved the performance of the wider than 50mm lenses on RED cameras. But unless they were literally curving the light coming out the back of the wider lenses to make them hit the sensor on a better angle, to an extent that visibly improved the performance of the lenses, I'm not sure what their point was. I'm big on the Skintone-Highlight OLPF's too, wheras the Leitz Leica-M OLPF's only came in the Standard OLPF variety as far as I know, so that's another factor to consider, and one that contributed to my not checking them out.