on 07/23/02 13:43, [EMAIL PROTECTED] shared with me:
> In a message dated 7/23/2002 12:28:43 PM Pacific Daylight Time,
> [EMAIL PROTECTED] writes:
>
>
>> It's been mentioned before that 100 ISO film pushed 1 stop should be shot
>> at 320 ISO and that shooting it at 200 ISO is not a 1 stop push. How valid
>>
>> is this?
>
> A doubling of film speed is a one stop push. Rating ISO 100 film at ISO 200
> is a one stop push, at ISO 400 it's a two stop push. This is the way I've
> always understood it.
>
> I found this, however, on the Kodak web site:
>
> "With longer development times, such as those used in push processing, EI
> values actually do increase, but only slightly. Underexpose a film by two
> stops and give it a two-stop push, and the real film speed will typically
> increase by perhaps a half stop. This means that the film is really
> underexposed by only 1 � stops, not two stops. But it is underexposed. "
>
> So, rating ISO 100 speed film at ISO 400 is only a 1 1/2 stop under exposure.
> Hummm....
Making an assumption, I'd say that the push processing of film is akin to
long exposures. The longer you expose a film, the longer you must actually
expose it to get the exposure you were aiming for. I don't remember the
phrase for this, but it means if you expose film x for one minute, to
achieve what any exposure chart will calculate for you, you must really
expose for 1.5 minutes. Other films will need other adjustments (is it
Reciprocity Failure?) based on their inherent exposure properties. Sometimes
wrongly confused with developer exhaustion.
JoMac, Pentaxian
"Pentax, Quadraphonic, Betamax, Macintosh"
and above the rest.
k t,
s e n
Living life a w o
almost parallel to, r
yet ever so slightly o u t -------> f
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