This particular $10 Canon adapter for Fuji X mount is labeled K&F Concepts, but there are dozens of similar designs sold on eBay. Here are some Frankenstein-looking photos. Needless to say, the larger lenses feel really heavy and imbalanced attached to the tiny X-T1.
And here is an image of how I did these product shots. Just something quick and fun with a remote flash pointed at the ceiling and a white background (a white sheet would have worked, too, but I had this taped-together poster board out for something else that I was shooting).
Images with this adapter can be sharp IF you can get the subject in focus. This is a manual focus only adapter, and even with the excellent help of Fuji’s focus peaking assistance, the difference between being in focus and being out of focus is less than 1mm of turn on the focus ring. (Take a moment to let that sink in. Ouch!)
For objects closer than 10ft, 1mm means around 1/2 – 1″ distance (putting an eye out of focus in a portrait). For objects farther than 10ft, 1mm can mean a few to several inches distance (putting a person out of focus). Shoot lots, check and recheck.
Manual focusing on the 50mm and 15-85mm is also more difficult due to the lenses having thin manual focusing rings.
Also, infinity is really hard to nail with wide apertures (the lens stops past infinity probably to deal with focusing to infinity in extreme temperature differences).
Since this adapter also does not control aperture, to get the Canon lens to change aperture, you can try this nifty trick.
Mount the Canon lens on a Canon body with a depth of field preview button. Change aperture, hold down the depth of field preview button (don’t let go) and detach the lens. Viola!