35mm film rangefinder lenses on BMCC 6k full frame

Hi all. My first post here. I’ve searched high and low and can’t find an answer. I have a number of 35mm rangefinder film camera lenses (Leica M mount) that I love. I’m just wondering if they will have full coverage on the BMCC 6k full frame? I’ve shot tons of 35mm still images with these and used them on APS sensors but never been able to use them with a FF sensor.

Does anyone know if they give me full coverage wide open? Obviously with an M/L adapter.
Thank you in advance for your help

I can only confirm that Russian rangefinder lenses (pretty much copies of early Leica ones) cover on a Sony FF alpha series camera.

I use rangefinder lenses (M and LTM mount) on full-frame digital cameras all the time; they're among my all-time favourite lenses. There won't be any problem with coverage on a full-frame sensor but you may notice some corner smearing and other issues with the wider lenses, depending on the thickness of the BMCC 6K's sensor stack. Most lenses 50mm and higher will be totally fine, it's mainly 35mm and wider that can be problematic. In most cases even 35mm is fine but sometimes you'll see field curvature artifacts. There are other degradations in performance when rangefinder lenses are used on digital cameras with thicker sensor stacks, but those are mainly visible to pixel-peepers. You probably won't notice them unless you fall into that category.

On digital, these lenses work best on cameras with a thin sensor stack, like Leica M-mount cameras. The Nikon Zf full-frame mirrorless camera does pretty well with wide-angle rangefinder lenses, but Sony cameras generally have problems with the wider ones unless you modify their sensor (Kolari does an ultrathin sensor mod for about $300 that greatly improves the performance of these lenses on Sony cameras). On a camera with a thick sensor stack you may see corner smearing and noticeable field curvature issues on wider lenses (e.g., the outer edges of the field will be in focus when they should be out of focus). The Sigma fp also shows these issues with wider rangefinder lenses.

For an extreme example, here are a couple of shots taken with the 28mm MS Optics Apoqualia on Sony A7iii full-frame camera. Note the blurry/smeared corners; the vignetting is normal and even occurs when I shoot this lens wide open on a 35mm film camera, but the corner smearing only occurs on Sony and other cameras with thick sensor stacks.

Just before sunset by Brad Hurley, on Flickr

Riviére des Prairies, Montréal by Brad Hurley, on Flickr

In this photo, taken with a Voigtländer Ultron 35mm/f2 rangefinder lens on Sony A7iii, you can see the effects of field curvature where the people at the edges of the frame are in focus when they should be out of focus. This doesn't bother me, but it bothers some people as it looks unnatural. The effect would be less pronounced on a Leica M camera or a Sony with a modified sensor stack.

Rain dancers, Royal St., New Orleans by Brad Hurley, on Flickr

So performance of wider rangefinder lenses all boils down to the thickness of the sensor stack on the BMCC 6k. You won't have any problems with coverage, although note that most wide angle lenses will vignette at their widest apertures (they even vignette on Leica cameras, that's down to the lens, not the camera). But you may have some issues with corner smearing and other image degradation with wider lenses such as 28mm, 21mm, and wider depending on the thickness of the sensor stack on this camera.

Just be sure you have some neutral density filters that fit those lenses; some M-mount rangefinder lenses have unusual filter thread sizes. I've had good luck getting hard-to-find filters from filterfind.net. You will need ND filters much of the time unless you're always shooting in lowlight conditions.

Thanks both of you for your responses. This is a huge help.

I've been so enamored of my Zeiss Sonnar 50mm 1.5 on my 35mm Leica film camera and was worried it wouldn't work on the BMCC6k. So I'm super happy I should be fine there. I have a cheaper 35mm M lens (7artisans' version of a 35mm Summilux) so I'm not really concerned about that one as I have a Contax Zeiss SLR lenses in that focal length. I also have a Rokkor 90mm M-mount that is a sleeper lens for me and I was hoping to use that.

So I'm really happy to hear that the lenses I like the most should be good to go.

Brad, those example images are gorgeous. Thanks for sharing!

All my Leica M lenses cover and work great.

JB

https://flic.kr/p/2qpQBoj

The ones I use are a Russian Jupiter -3 (50mm f1.5) and a Jupiter-9 (85mm f2), and also an Industar 52mm f2.8. The Industar is pretty funky and was a bycatch on a Zorky camera, it's rarely used.

I love those two Jupiters for their nostalgic look wide open, and they get pretty sharp into the corners when stopped down. The 85mm looked thoroughly battle-tested, and had its focus nearly stuck. But it got excellent service by a local specialist, a retired engineer from Voigtländer, and now I enjoy it for portraits. Note how the OOF highlights stay round when stopped down, due to the high number of blades for the aperture. It's just as old as I am, and still slightly off center, as you can see in the lower left corner.

Nobody wanted their portrait published right now, so here's a quick test rectangular to a Rattan bench. Focus is on the center of that bench, and the stop is f5.6:
https://drive.google.com/file/d/1LKou2J ... sp=sharing

I've been so enamored of my Zeiss Sonnar 50mm 1.5 on my 35mm Leica film camera and was worried it wouldn't work on the BMCC6k. So I'm super happy I should be fine there.

That's a wonderful lens, it's my preferred lens for portraits although I don't use it much on my Leica film camera due to the severe focus shift (which makes focusing with the rangefinder unreliable except at certain apertures). It works great on my Sony full-frame cameras since focus shift isn't an issue when you're focusing through an EVF or the LCD screen.

One caveat to keep in mind: lenses with character exhibit that character mainly at wider apertures; stopped down all lenses look pretty much alike apart from subtle differences in rendering, colours, contrast, the shape and number of points in sunstars, etc. So if you want to employ the character of your rangefinder lenses in video, you'll need to shoot wide open or close to it. And on full-frame cameras that becomes a problem due to shallow depth of field, which makes maintaining focus challenging.

On APS-C and smaller sensors, you can fill the frame with a subject from a greater distance due to the so-called crop factor. Greater distance gives you greater depth of field. With the same lens on a full-frame sensor you need to get closer to fill the frame, and your depth of field will be shallower. If you open up the aperture to get the most character from your lens, that will decrease the depth of field even more.

I can maintain focus fairly well when shooting video of dancers in dimly lit halls using my original Pocket and Micro Cinema cameras with a fast lens wide open, but those cameras have tiny sensors, Super 16 size, which is smaller than Micro Four Thirds. I tried using my Sony full-frame camera for a dance shoot last year with similar lenses and it was next to impossible to maintain focus; I ended up setting a focus point and let the dancers drift in and out of it.

Wide-angle lenses will give you more depth of field, and you may have better luck maintaining focus with those on full frame than your 50mm Sonnar or anything longer than that, unless you're mainly shooting video of things that don't move much.

I'm revisiting this for the benefit of whomever might be interested. I shot a very quick lens comparison including the Zeiss Sonnar T* 50mm 1.5 ZM along with some of my other vintage film lenses. YT link is below. This was just very quick and non-scientific. Actually, this is the first footage I've shot on the BMCC 6k Full Frame.

I was impressed with the Sonnar and happy to see it's going to be a good option for the full frame sensor on the BMCC. Also, I was pretty impressed with how consistent these various lenses with one another. Not identical by any stretch, but nothing beyond being able to manage in the color grade stage.

Thanks all for your help and advice.