Scapevision wrote in post #15975837
Yes they do, everything works as with stock screen. I use a focusingscreen.com screen with microprisms. Switching was a matter of unscrewing 2 small screws.
Well, not everything will still work...
If you go to a focus screen with a split image center spot (which is what you'll want for manual focus with larger aperture, shorter focal length lenses), your 7D's Spot metering will no longer be accurate. It might effect Evaluative metering, too, if and when the center AF point is the selected or primary active point.
Most manual focus cameras had both the split image center spot and a "donut" of microdiaprisms around it. The center spot, as mentioned above, works best with shorter focal lengths and larger aperture lenses. The microdiaprisms work best with longer focal lengths and smaller apertures, where the split image is difficult or impossible to use.
If you don't already have them, I wouldn't recommend buying Canon FD lenses with plans to convert them. It is possible, and some FD lenses are great, but they are tricky to convert and only certain lenses can be used fully (many lose infinity focus, unless you use an optical adapter that costs a lot of image quality).
Instead I'd suggest you choose among Nikkor F mount, Oly, Pentax, Contax/Yashica, M42 and a host of other vintage, manual focus lenses that are very easily adapted for use on modern Canon cameras. See Bob Atkin's website for a lot more info about this.
I can't personally recommend one brand or another of adapter. I don't have a whole lot of conversions, but do always use the chipped type, since they give me Focus Confirmation and I usually just buy generic off eBay or Amazon. I also have several modern manual focus lenses (tilt-shift, for example), but I do not find it necessary to change out my camera's focus screens. Focus Confirmation, a magnifying angle finder and the rear LCD on the camera are all adequate focus assists for my purposes.