Lars Michael wrote:
> > This statement sounds contradictory to the equation introduced earlier
> > (remember that you said manufacturers assume ISO 100.
> I read the original statement again, while it may seem a bit misleading, I
> understand it now.
I don't know if it's misleading, but I can see how it's confusing. A
better approach probably is to distinguish between "EV100," the luminance
equivalent for ISO 100, and the "EV" used to determine camera settings.
Then, from
2^EV = A^2/T = LS/K
one obtains
2^EV100 = L * 100 / K
L = K/100 * 2^EV100
and
2^EV = LS/K = K/100 * 2^EV100 * S/K
= S/100 * 2^EV100
Of course, "EV100" really doesn't have any meaning unless you know K,
although the difference between the two common choices (12.5 and 14) is
only 1/6 step.
My statement
> So in this sense, the change in EV is linear with ISO speed
was sloppy--it's obviously "2^EV" rather than EV that's linear with ISO
speed. I suspect that's actually what Carlos and I both were thinking.
> Here's a little table I use to "translate"
> EV to camera settings:
Would seem to cover most picture-taking situations ...
Jeff Conrad
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