Originally posted by Cannikin A 100% coverage, 1x magnification APS-C viewfinder will appear exactly the same as a FF viewfinder with 66% coverage, 1x magnification. Does that clear everything up?
No, while true, it is extremely misleading.
The full formula for virtual viewfinder size is
Magnification x coverage/100% / cropfactor
Of course, you can interpret (coverage/100% / cropfactor) in any way as long as the quotient remains the same. And of course, 66%/1.0 = 100%/1.5.
But your interpretation makes no sense and will confuse people.
By convention, coverage is expressed in relation to the sensor/film and we don't want to change this.
By convention, magnification is expressed in relation to a 50mm lens and even this nobody wanted to change.
Therefore, a third factor, the crop-factor, is introduced to express virtual viewfinder size (cf. formula above).
The "
35-mm equivalent magnification" is (Magnification / cropfactor) and expresses magnification wrt to a lens 35-mm equivalent to 50mm. It is crucial to evaluate the ability for manual focus thru the VF.
Your statement is misleading because it assumes that an APSC and FF camera would use the same lenses while they don't.