DIGICHombre

I have a voitlander 75mm f/1.8 that works very well with an anamorphic, specifically Kowa C-35. On full frame Sony A7 series there was no vignetting.
The one big catch is this lens was meant for rangefinder cameras I believe, so slapping it on a foal reducer on a crop sensor effectively turns it into a macro lens, and quite unusable. Haven't yet tried on Canon, or any other body yet. All I know is it needs to get pretty close to the sensor. Great photo lens nonetheless.

Lovely grade. Fuji film stock looks so vintage. 

Hi, I'm interested in purchasing this but I don't quite understand how it connects to an anamorphic lens? How does that gold slip ring stay secure? Is it customized fit for every vintage lens ?

Very easy to dismantle DNA...I modified mine myself. It is only the larger Inflight 1.75x that can be a bit of a pain to get it working with - other lenses (such as Kowa B&H/ 8Z etc) will work fine with the standard 75mm rear opening. Optically, the DNA is probably the best choice for now in my opinion - just don't expect precision engineering out of the box (it wobbles and makes a horrible noise when focusing) but that can be adjusted and the optic quality just about makes the price worth it IMHO. 
I tend to shoot with an old 100mm meyer optik f2.8 zebra - set no wider than f4 on full frame. Gives good all round performance and sharpness at that stop.
All vari-diopters increases the apparent defocus bokeh, so f4 can be plenty shallow enough. DNA/Rectilux/FM module/ SLR Rangefinder are all single element design to their diopters, so fast open apertures are always going to show aberrations/glow/blur of some kind. Achromatic optics (if even they could be made at scale) would be horrendously expensive and noticeably heavy but would solve this issue.
How close do you align the kowa rear element to the taking lens?
I have my setup as rail mounted - so I either attach taking lens via an empty cpl ring (so taking lens can turn into camera mount whilst still attached to everything) or simply by pushing the kowa rear as close as possible to taking lens front, using a rubber collapsible sun hood as a donut. The optic rear of the Kowa is protected by collision by a uv filter and its diameter, relative to the taking lens front. It's a setup that I find can work very well. The other advantage of having the setup rail mounted, is that i can mount a VND to the rear of the kowa and in front of the taking lens...this works very well.

Hello,
I have this exact Voigtlander 40mm Ultron, and have used it with anamorphic adapters. First, the lens is amazing by itself. One of my favorites. 
With anamorphics, in my experience, I haven't found it vignette free, if you're shooting on a full frame sensor. Anything smaller and you have a bit more flexibility but I've used SLR Magic Anamorphot and Kowa adapters and they both showed obvious corner darkness.

I would start calculating from a different point but the end results are the same:
 
target aspect / squeeze x vertical resolution = horizontal resolution
 
2.35 / 1.5 x  1080 = 1692  (1692x1080)
 
2.35 / 1.5 x 720 = 1128     (1128x720)
 
2.39 / 1.5 x 1080 = 1720.8 (1720x1080)
 
2.39 / 1.5 x 720 = 1147.2 (1148x720)
 
This way you have the least amount of rounding errors.