When you write "vintage lenses" are you referring to vintage manual focus, manual aperture lenses without any electronic communication or to older EF mount lenses with electronic AF and aperture (either of which can be adapted to use on EF-M mount cameras)?
If it's the older manual focus/manual aperture type of lens, you have to set "allow shutter to fire without lens on camera" in the menu to use them. The reason is because the lens has no electronic communication with the camera,so the camera doesn't "know" a lens is installed, By default, the camera is designed to not allow the shutter to be fired without a lens, so this override is needed. Setting it to allow the shutter to work doesn't change anything when using the camera with more modern lenses that have the electronic communication (both lenses in EF-M mount and adapted EF-mount lenses).
Incidentally, there are also modern lenses that are manual focus/manual aperture, that require this menu setting to allow camera to "shoot without lens".
Finally, when using any lens without electronic aperture control, you will have limited use of the exposure modes. "M" or fully manual mode will work, of course. "M + Auto ISO" also should work. "Av" or aperture priority mode also should work. Experiment with them on your camera to see if they work okay. But, "P" (program) and "Tv" (shutter priority) will not. Both of those require the camera have means of setting the lens aperture, which it doesn't with this type of lens. The "scene modes" such as "sports", "landscape", "portrait", etc. will probably also not work. (I honestly don't know because I never use them).
Hope this helps!
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5 and some other cameras, various lenses & accessories
FLICKR & ZENFOLIO
