The Canon EOS Rebel SL2 (200D). I saw that in the manual. But Canon didn't really explain it other than that it slows down the framerate. What does it do?
The manual doesn't really explain it, but I googled, and it looks like all it does is slow down the speed of the mirror. The mirror still goes up and down for each shot same as in all other drive modes. I guess a slower-moving mirror might produce less vibration, but would have to test it at a long enough focal length to find out. Might be worth checking out though.