Quote Originally Posted by Stephen Benskin View Post
I'm surprised you don't remember either thread. The 1.0 ratio is the reason why there's a consistent discrepancy between ISO speeds and Zone System EIs.

The proof for the ratio is with exposure meter calibration and how it relates to the metered camera exposure point.
I sometimes skip or ignore threads and posts that say "zone system" so I may have missed that. I do remember a thread where I was posting about uncertainties in zone exposure being at the beginning, middle or end of the zone, so it was probably in that thread.

But is the "1.0 difference" a definition? If so, wouldn't all meters be required to have the same "k" constant?