Actually, I believe it was Hasselblad who first presented the idea of using round, flat mirrors to square away the camera perfectly (they claimed 2/60 degree accuracy), but their device, called the Linear Mirror Unit used two mirrors, one mounted through a T-mount onto the camera body. http://www.clubhasselblad.com/hassel...ar-mirror-unit
Using one mirror can get accuracy above 90% quite easily, but if you use two opposing mirrors, you get crazy degrees of accuracy, provided the mirror on the camera is mounted parallell to the film/sensor plane.
Now, imagine using a view camera, a normal to longish lens and front rise to repo any kind of reflective artworks through glass or large, moderately flat areas of reflective oil paintings.
Waah, all the old bird secrets come out liao. Wonder if the newbies know how to use or not.
In this day and age, not much secrets liow lar. As catchlights said, sometimes tell the secrets also on one believe, think you are kooku
I get paid more shooting part time ...... damn, I should find more time to shoot part time