Thanks for this response to Wayde's request for further clarification of my
statement. Not being much of a mathematician I knew myself to be in trouble
when he wrotee "y = Mx where M is the proportionality constant."
Your chart is an accurate representation of the silver curve, on bottom,
and the silver plus stain (on top). It certainly is much cleared than my
original comment re: linerity and prportionality.
Sandy King
>Perhaps this attempt at a graph may help explain what Sandy is saying.
>Think of the "o's" as silver density and the "x's" as silver plus stain
>density. While each of these hypothetical lines is linear, their slopes
>are different. The bottom line (no pun intended) is that there is a
>greater amount of stain in areas of higher silver density, therefore the
>difference between silver density and silver plus stain density becomes
>greater as you move up the scale. And, to reiterate, because platinum
>sensitizer is only sensitive to UV light and the UV light is very blue,
>proportionally more of the UV light is blocked by the yellow-green stain
>of the Pyro developer as silver density increases. This is what causes
>Pyro negatives to exhibit higher contrast relative to UV light than
>conventionally processed negatives.
>
>I hope this helps and hasn't further confused the issue!!
>
>|
>| x
>| x
>| x o
>| x o
>| x o
>| x o
>| x o
>| o
>|----------------------------------
>
>
>Also, Carl mentioned FP4+. I very much prefer to use this film over my
>other choice (since I shoot 7x17 my practical choice of films is
>limited) which would be HP5+. FP4 has a much clearer base than HP5, and
>this goes for "standard" developers as well. I also have found that I
>prefer the scale of FP4 and the look of the prints made from FP4
>negatives over HP5. I do occaisionally shoot HP5 when I absolutely need
>the film speed. I agree with Carl that the film base plus fog level is
>approximately the same for pyro and non-pyro negs. Since there is very
>little or no silver in the non-exposed parts of the film, there is also
>very little or no pyro stain. Terry's suggestion that the negative is
>awash with a brown muck simply indicates that he has never tried it.
>Conversely, I've yet to try Terry's beloved acid-amidol, but I do intend
>to. My mind is open!
>
>Kerik Kouklis
>http://www.jps.net/kerik/
>
>
>> On Thu, 29 Jan 1998, S. Carl King wrote:
>>
>> > 2) There is a linear but not proportional relationship between the
>> silver
>> > and stain densities (of the PMK processes negative) as exposure
>> (time of
>> > devleopment) increases.
>>
>> I could use more explanation here. How can something be linear but
>> not
>> proportional? As far as I know a linear relationship is directly
>> proportional (example: y = Mx where M is the proportionality
>> constant).
>>
>> - Wayde