Khun Hans wrote:
Yes, John understand what you say. What I was trying to say is that it is either a so-called crop in terms of FOV on a smaller sensor or an extension on larger film/sensor.
Not so much, there's nothing special about the 35mm format other than it's what most people are familiar with. The entire thing about 'crop' comes from the introduction of cameras with 35mm format lensmounts with sensors that are smaller than 35mm so that people could quickly get an idea about how a lens would behave on the new, smaller, sensors.
Prior to that it was generally just assumed that one could figure things out based on what the normal length of the format is (which is about 43mm for 35mm format, 29mm for APS-C digital, 75mm for 645, 150mm for 4x5 Large format.. etc)