Sandman
Which people understand when you talk about ISO 200 or ISO 6400 because those numbers are easier to understand. While few understand it's "only" five exposure stops between those values and they may seem like a larger difference than what they really are, the entire system falls apart when you compare ISO 102,400 with ISO 3,276,800, which is also a five stop difference.

Eric Stevens
What's wrong with 3.2 MISO?

Sandman
There's nothing inherently wrong with it. And since most people learn quickly that ISO is an arithmetic scale, they know the value doubles for each stop.

And thus, most people can easily calculate in their head how many stops of difference there is between ISO 800 and ISO 3,200.

But, how many stops are there between ISO 51,200 and ISO 3,276,800?

It's becoming increasingly unwieldy.

Eric Stevens
Or at least it will be if these levels become the normal operating range for photographers.