"Severi Salminen" wrote in message
...
Dan Quinn wrote:
Another attempt has been made to dissociate ISO from EV. I'll leave it
up to the reader.

I believe that EV and ISO are inseparable. As those familiar know, the
EV does change as the ISO changes. Ipso facto. Dan

Correct! (If the light level and resultant film density are held
constantg.)

You are confusing EV and "correct exposure". EV is simply a
speed/shutter combo (all combinations resulting same exposure) and holds
no info on ISO, subject brightness, correct exposure etc.

Hmm. The dictionary at hand defines EV as being LV + film speed, where LV is
the light level.

In the APEX system: EV = AV + TV = BV + SV

Where all values are logs, AV is aperture, TV is shutter speed, BV is the
light level in foot candles.

EV does not change as the ISO changes. But it has to _be changed_ if the
user wants to keep the exposure on the negative the same. That is a
different thing.

As Lassi said, EV15 is allways 1/125s at f/16 (or 1/250, f/11 etc.) no
matter what subject, ISO or weekday.

It seems you're both right. The EV value for a given light level changes
with the ISO, but the shutter speed/f stop combination for a given EV is
always the same.

David J. Littleboy

Tokyo, Japan