This Voigtländer 40mm f/1.4 lens to fit LEICA M cameras is not for use on any LEICA M cameras other than the LEICA CL and theMinolta CLE, which are the only LEICAs with viewfinder frames for 40mm lenses. The only other camera with a LEICA M mount and a 40mm finder frame is the plastic Voigtländer Bessa R3M with 1:1 finder.
It would be foolish to use this lens on any other camera simply because no other LEICA M mount camera has a 40mm viewfinder frame. Used on other LEICA M cameras, this 40mm lens calls-up the 50mm finder frame, leading to very weak images which have far more in them than indicated by the viewfinder.
Yes, you could buy an accessory 40mm viewfinder if you are a total dweeb, but why would you want to torture yourself with having to use one finder to compose and another to focus when you could use a35mm lens, for which your camera will have a viewfinder frame?
You also could take advantage of the LEICA M9-P‘s very sloppy finder that shows much less than the actual image, and use a second finger to force the LEICA M9-P’s finder to the 35mm setting, and so long as you can hold it there, you’ve got a fairly accurate finder that shows just a little less than you’ll get on your frame. Since you’d have to keep a finger on the preview lever to keep it from defaulting back to 50mm, this isn’t a good idea when you should just use a 35mm or 50mm lens that will work properly.
This lens attempts to improve on the LEICA SUMMICRON 40mm f/2of the early 1970s, however that LEICA lens is usually sharper and has a little less distortion and used for less money than this lens, so why anyone would want this lens is beyond me.