Well, Mike, even if the meters are setup for a 13% gray, and
I still doubt that because as I have said my Sekonic 308
gives the same reading with light reflected for an 18% gray
card as it does in incident mode, all you have to do is
reduce your ASA by that amount and use 18% because all that
is affected by that is where the calculator scale is set
relative to the meter reading . The meter calibration is
actually done as I have describe here several times. BTW is
the difference between 13% and 18% 1/3 stop or is it 1/2
stop? (I don't have a scientific calculator any more).
--Tom
Mike Johnston wrote:
>
> Tom R. exploded:
>
> > I am the one who argues that this 13% thing is bull.
>
> Tom,
> Actually it's not. The ANSI standard is around 12% and a lot of
> manufacturers use 13%. Of course, as with film speed, the manufacturers do
> what they want to do, so many of them do calibrate to 18%. I wouldn't be
> surprised if some of them have enough tolerance built into their
> calibrations that they VARY from 12% to 18%! <g>
>
> Just because you get two meters to agree with each other doesn't mean all
> other meters are like those two. Try comparing a Nikon and a Contax meter,
> for instance.
>
> As I said before, Ctein has tested this and reported his findings in his
> book. His original source was Dick Dickerson, who is just a wee tad more
> authoritative than Bob Shell--Dick oversaw the development of the T-Max
> films, Polymax papers and chemicals, the Kodak chromogenic film, and Xtol,
> among other things.
>
> You want me to ask Dick about it? Or Ctein? I will if you want. The thing
> is, I really think that since Ctein went to all the trouble to write it all
> down in his book, the least we can do is give him the courtesy of going to
> read about it there, instead of asking him to rewrite it again in an
> individualized e-mail. But I'll ask him if you'd like me to.
>
> His book is called _Post Exposure_, Focal Press (www.bh.com), ISBN
> 0-240-80299-3. The whole book is well worth having.
>
> --Mike
>
> P.S. Mark Roberts, No, I don't know the title of the relevant ANSI document,
> but perhaps I can find out.
>
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