I was reading this thread on another chat board, and they were discussing the normal FOV lenses like the 50mm lens on a 35mm camera. The way I read it, to figure out the normal FOV lens for a given media you measure the diagnol of the sensor or A squared + B squared = C squared. According to this method of thinking, a 35mm(36 x 24mm) film camera would need a 43mm lens. The thread went on to say that since no 43mm lens was available, photgraphers adopted the 50mm lens as the normal view lens. According to this philosphy to get a normal view lens for a Nikon D70(23.7 x 15.6 mm) you would need a 28mm lens, Canon 20D(22.5 x 15mm)a 27mm lens, 6x4.5(56x42mm) 70mm lens, 6x6(56x56mm) is a 80mm lens (79mm actually, rounding up to 80mm), and 6x7(56x67mm) is a 90mm lens (87mm actually, rounding up to 90mm). Here is the thing I need help with. If you use a 50mm lens on a 35mm and you want the same angle of view on a APS-C camera you would use something close to a 35mm lens. If your intention from the begining was to get the angle of view that the normal eye sees, would you use the 28mm lens or still use a 35mm lens? I am not sure on all this math stuff when it comes to Field of View and Circles of Confusion stuff. Infact it can all get kind of confusing to me. Is this formula correct on normal angle of view lenses?