'Convert' your APS-C to FF camera

"As we reported recently, the Speed Booster is an adapter that allows for a full frame lens to be mounted on APS-C or Micro Four Thirds mirrorless cameras. There are two reasons why this is very big news, and both revolve around the optics inside the adapter. Firstly, Metabones claims that by reducing the image magnification, the Speed Booster produces roughly a 1.09x focal length multiplier, promising a nearly full frame field of view on APS-C. The second claim, as its name implies, is that the Speed Booster increases the lens's speed by a stop, turning an F2.8 full frame lens into an F2.0 optic that allows for low light shooting at a lower ISO sensitivity."

http://www.dpreview.co​m …s-metabones-speed-booster

initial reviews are good. I'm considering getting this

This only works on mirrorless cameras (as it needs to reduce the distance between the lens and the sensor). Are they working on an EOS M version?

gcogger wrote in post #15558991
Are they working on an EOS M version?

Doubtful. It's a niche item and EOS M has very few owners.