Really people, I cannot but wonder. I thought this forum had evolved into a more mature one. My bad.

Equivalence is a theorem, not a belief, religion, argument or opinion. As such, it needs to be taught to newbies not knowing it yet.

The fact that normalizing 1. focal length, 2. fstop, 3. iso leads to a specification of a photo's capture parameters which are

*entirely independent of sensor size* (i.e., the sensor size cannot be deduced from the resulting photo's properties, even if you look at noise or diffraction or bokeh or other artefacts) is a surprising yet

*fundamental truth* which any knowledgeable photographer needs to know and to use in a discussion involving more than one sensor size. It is now a textbook content for any lecture on photography. Just like fstop is.

As such, it isn't trivial at all. To many, it comes as a surprise so big that they can't understand it. It isn't clear a priori that the equivalence normalization has this property. After all, e.g. if you look at "depth of field" formulae, it seems to depend on focal lengths and image circle diameters ... Equivalence is the beautiful theorem that it and any other optical property doesn't upon closer inspection. I.e., a camera can be specified 100% without specifying its image circle.

All this debate just obfuscates this simple to state yet powerful and therefore inherently beautiful truth. It is driving me nuts if I see people trample on beauty.

I'll leave this topic alone now (in this thread). I only contribute to few threads on PF anymore nowadays. The experience in this thread wasn't a rewarding one. Anyway, the topic was K-3, right?