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Michel Rabe wrote:Why? Personally the analogy made it much easier for me to understand the concept of exposing for raw when I got my first RED camera. I remember how many people on REDuser had to rethink exposing and how RED tried to educate everyone.
Michel, I think what John means is they are really very different; the analogies are sometimes just that. For example it was common to get a 'thick' negative, back in the day, by over exposing (conversely it was advisable to underexpose reversal stock); because negative film could be pushed and pulled in development considerably, and highlight fell off gracefully. Whereas digital is really video with a log curve and raw; but highlights will still clip eventually in an ugly way. And so here ETTR which may be considered a broadly similar and analogous approach may not be suitable, in the same way.
ISO is really a complete fiction, in the sense of photochemical equivalence, that is; it is really db digital gain simply, with fixed 1 or two ADC amplitudes. Your selection of ISO/db does obviously influence your exposure settings choice and raw allows more latitude in post, analogous to negative film, but that's where it ends with real ISO or ASA, or whatever. ISO comes mainly from stills anyway, from the DSLR craze; it was more common to think in ASA back in the film days.
The incredible latitude of of Digital film cameras now does approach film and in some ways exceeds it; and these terms have most certainly helped the almost total transition to digital, so you are right too, they can be very helpful in the end. But the terminology is strictly analogous not scientific.