On Oct 31, 8:00 pm, Peter Irwin <pir...@[EMAIL PROTECTED]
> wrote:
> UC <uraniumcommit...@[EMAIL PROTECTED]
> wrote:
>
> > It is my opinion, and that of many others, that the 'new' ASA speed
> > sytem introduced in 1959 gives numbers that are too high, by about 2/3
> > stop.
>
> I think the primary reason for this is that the question
> you want the ISO rating to answer is a different question
> from the one it was designed to answer.
>
> The question the speed rating is designed to answer
> is "what is the minimum exposure required to produce
> a negative from which a print judged to be 'excellent'
> can be made?"
No, I don't think so.
It was "What index will produce the greatest number of correct
exposures without losing definition through overexposure on automatic
cameras".
You have to remember that the late 50s saw the introduction of
numerous compact, semi-automatic and meter-coupled 35mm cameras with
primitive meters.
The way these cameras metered resulted in overexposure errors more
often than underexposure errors, if I recall correctly. It was felt
that a reduction in exposure was warranted because of this.
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