Whisky-dave
So in your new world would 15 ISO be a fast or slow 'speed'

Sandman
"fast" and "slow" was only ever used in relation to analog film, no one is calling "ISO 6400" a "fast" sensor setting or whatever.

As for what ISO EV+15 would be - see my OP, I had a table in it.

Whisky-dave
I doubt I'd have any trouble working out what 12,800

Sandman
Which is why it's only a problem now when we have ISO values of 3,200,000 and 4,000,000

Whisky-dave
but it's not if you just use whats called teh significant bits/number like you have above why is 4 million ISO so complex it's twice as fast as 2 million and half the speed of 8 million ISO or 8M just like we do with semsor sizes and hard disc sizes.

Sandman
Right, but how many stops faster is ISO 4,000,000 to ISO 51,200? Not so easy to calculate in your head any longer, now is it?

For the answer, ISO 4,000,000 is 6 stops faster than ISO 51,200. Just as ISO 6,400 is six stops faster than ISO 100.

Whisky-dave
would have meant either. which is why DIN or EV would be better than ISO as sensitivities increase as they do today.

Sandman
Which incidentally, is what I'm saying. In fact, the old arithmetic ASA standard had a logarithmic equivalent later called APEX which is very similar to what I am proposing, where APEX 5° = ASA 100 and APEX 6° = ASA 200 etc etc.

Whisky-dave
So why change it then, no one really used APEX because there was no reason to.

Sandman
Since the ISO range was limited and not that easy to calculate in your head. Mostly it went from ISO 100 up to a whopping ISO 1600. So using an arithmetic scale with those few numbers is easy. When using an arithmetic scale with values from 100 to 4,000,000 it's no longer as easy.