Intuitively, I think a small plane mirror will act "like" a pin
hole. A member of tap-l claims that a large mirror (eight inches
diameter) will do the same if the "focal" length is long enuf.
(logically meaningless). He then backed it up by experiment. i.e.
nice image at 50 feet.
My calcs. (remember I'm maths challenged) predict that image was ~
five inches and (with ray tracing, trig, and algebra) the "circle of
confusion the same as the radius of the mirror (what ever the
distance). So am I very challenged or is the tapper ...?