Sandman
So with the D5, it can boost its ISO to ISO 3,280,000, and suddenly how ISO is named is becoming just stupid. We should use EV steps instead:

Whisky-dave
SO why start at -1 ?

Sandman
The base would be what is today called ISO 100, which corresponds to an expected brightness level of the resulting bitmap image.

Whisky-dave
Why limit it to bitmaps?

Sandman
Because ISO is film sensitivity and sensor amplification, so it's only a variable for the resulting image.

Whisky-dave
which might not be a bitmap image BMP.

It'sz got nothing to do with sensor amplification eithert.

Sandman
So ISO 50 is one step lower than that, naturally.

Whisky-dave
not a 'step' but half I'd say.

Sandman
No, going from ISO 50 to ISO 100 is one full stop. The scale is arithmetic, remember. Each stop is a doubling of the value. ISO 100 is one stop more sensitive than ISO 50, just as ISO 800 is one stop more sensitive than ISO 400.

Whisky-dave
yes so, my point was that most cameras you normally set to fixed common ISOs 100, 200, 400, but with DIN the was more choices as thre were with film. you said 50 and 100 like you have to use either of those are you forgetting 64 and 80 ? DIN 19 and 20

are you sure about that as it makes NO sense or is it nonsense. Doubling the ISO effectively doubles or makes it twice as sensitive to light meaing you only need half the exposure.

Sandman
Which people understand when you talk about ISO 200 or ISO 6400 because those numbers are easier to understand.

Whisky-dave
I don;t remmeber having problems when I was exposing film at 10 ASA up to 6400 ASA

Sandman
Which is what I just said...

Whisky-dave
so why change it

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

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.

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
So any given exposure has an exposure value. Using ISO, you can then amplify the signal by one or more stops to emulate a different EV.

Whisky-dave
That's no use though is it as the EV is fixed that's the point. It represents brightness as seen from the sensor or film plane, that's why it's useful.

Sandman
So, shoot an image with 1/250 shutter speed at f4. That results in a bitmap with a given brightness. Now, change the ISO to 200 and that result would be amplified to be an equivalent EV as if you had used 1/250 f4 or 1/250 f2.

Whisky-dave
So that doesnt; change the amount of light on the sensor does it, so the lighting level is the same that's why you get the same brighteness.