Originally posted by kadajawi The K mount would be a bit of an issue, cause it is rather adapter unfriendly, unlike those mFT cameras, but otherwise...
Ahh Grasshopper, much to teach of shopping there is....
So far, I've found decent secondhand K-mount lenses have a much lower price premium on them compared to similar specification EF and Nikon glass.
Now, given the sheer volume of Sheeple who buy Canon ( because, y'know, everyone has Canon,.. ), if you work with people who insist on shooting on any Canon with an APS-c sensor, a K-mount to EF-Mount adapter ring is a useful choice - $10(AU) gets you a ring that will do the job nicely.
Because the Flange-Sensor distance is longer on the K-mount, something like 3mm longer then the EF mount, and almost double the length of the NEX and MFT mounts, you can always stick the K glass on other cameras, but not be able to go the other way.
This also means, if you combine a FF K-mount Lens, with an EF ring, and a Metabones 'SpeedBooster' EF to MFT mount, you can get a truckload of light on to the sensor of a BMD-CC,.. Iff they ever get the MFT version out to customers...
And of course, as a full manual lens, with a proper Iris ring, a nice classic K-mount lens gives a 'look' that none of the Canon glass imitates.
I've had my Pentax and Sigma lenses on a 7D with good results, and on a 550D with Magic Lantern installed, and gotten some beautiful and cinematic looking footage.
With the Cinestyle profiles and ML controlling the 550D camera, and letting us ramp up the data rate to the maximum we could get out of the SD cards, and with my USB/DMX controller rig to match the lights to our chosen aperture/ISO, we were able to shoot dark moody scenes, that we just wouldn't have gotten with the available Canon Lenses for that short film.