The image is flipped by the mirror, then flipped again by the second mirror...
The Aperture!; The Aperture works like a human pupil, opening wider for aceptance of more light, or slimming to reject light.
Shutter Speed; Controls the speed of shutter, the quicker the shutter, the less light is allowed through, the slower the shutter, the more light is allowed through!...
Rule Of Thumb!: While Using A Handheld Camera You Shouldn't Got Below 1/25th Of A Second...
D.O.F! Depth Of Field; The wider the aperture, The smaller the depth of field,
the smaller the aperture the bigger the depth of field.
Http://www.photonhead.com/simcam/shutteraperture.php