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?

Whisky-dave
No it isn't but not much more difficult working out anything else that yuo get used to.

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.

Whisky-dave
limited in what way ? and I can calculate it in my head even more easily than aperatures, but no calculation is needed you just memeorise it. Tell me how or why you calculate £5.6 lets 4 times the light it than f11. How did you calculate it ? No one calculates it anymore, unless you're learning photography.

Sandman
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.

Whisky-dave
Which is why DIN would be better as A it would have less digits B it'd be the same systems as sound. You could also then have a light signal to noise ration in DIN presently with IOS it's virtually impossible to work out.