"pico" <pico.pico.net> wrote in message
news:13iic4e3pc0a24b@[EMAIL PROTECTED]
>
> "Peter Irwin" <pirwin@[EMAIL PROTECTED]
> wrote in message
> news:fgb4vl$o0s$1@[EMAIL PROTECTED]
>> UC <uraniumcommittee@[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?"
>>
>> The question you probably want answered may be
>> something like "What exposure meter setting will
>> consistently give negatives that are easy to print
>> well?"
>>
>> The answer to the second question is going to generally
>> be a lower exposure index than the ISO standard.
>
> MOST EXCELLENT observation. Kodak set the metrics. Those
> are the same folks who conducted a hugely expensive and
> detailed survey of average customers (largely of automatic
> processing) and Kodak set their metrics to those
> standards, as abysymal and utterly tasteless as they were,
> they still represented the drug-store processing majority.
> (Imagine the Bell curve - who wants to live on top?) Oh,
> and what camera did Kodak come out with in response to
> that study? The wholly embarassing failure, the Disc
> Camera!
>
> But to add a contem****ary data point - with so many people
> scanning negatives, a whole new scale must be developed
> (no pun). Me, I'm still scanning prints. So shoot me
> already. :)
>
This is simply not true. The Kodak speed method was
developed over a very long time by quite valid research all
of which has been published in peer reviewed journals. Much
of the work conducted under L.A.Jones leader****p was
published in the Journal of the Franklin Institute.
There is a big difference between market surveys and
scientific investigation and you are confusing the two.
Kodak's main thrust has always been to make photography
practical and easy for amateurs, that's what George
Eastman's philosophy was and he built one of the most
successful businesses in history on it. The influence is
still there even though Kodak has moved from chemical to
electronic photography.
Actually, the ISO speeds are quite practical but many
photographers do not understand how they are supposed to be
used. The speed applies only whan the specified developer is
used and when film is developed to the same contrast index
as is used in the standard measurement. This is about the
contrast for contact printing and diffusion enlarging. If
film is devloped to a lower contrast the exposure must be
increased.
Also, Jones found that the quality of the prints changed
little once the minimum exposure was reached. Minimising the
exposure minimises the density of the negatives, which, in
genera, is better for minimising grain and maximising
sharpness, however, it is often the case that increasing
exposure a bit improves tone rendition, perhaps because of
errors in using an exposure meter.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]
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