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Re: filmscanners: Grain in Color negative Film



At 18:30 23/03/2001 +0000, you wrote:
>On Fri, 23 Mar 2001 20:31:23 +1100  Roman =?iso-8859-1?Q?Kielich=AE?=
>(panromek@bigpond.com) wrote:
>
> >  Grain pattern is
> > dependant of the film structure, not developer.
>
>Up to a point. The precise agents used and solvent action of a dev can make a
>huge difference to grain. EG TriX or HP5 can be absolutely marvellous in deep
>tanks, as they accumulate a higher concentration of sulphite and halide. It's
>virtually impossible to match this in one-shot processing. I have tried
>modifying several developers by adding sodium sulphite and HC110 in 
>particular
>gave much reduced grain using it.

true, but don't mix B&W with color processing, they are two different 
animals. You don't have that sort of freedom in processing C41 films.


>It seems unlikely that all C41 devs use the same dev agents or solvent 
>content,
>so some variation in grain would seem quite rational, to me.

ALL C41 kits use CD4 as a developing agent, if not, you can sue the seller 
for selling the product not fit for the purpose.  C41 developer consists of 
2 g/L hydroxylamine salt, 4.25 g sodium sulfite, 1.3 g sodium bromide, 37.5 
g potassium carbonate, 4.75 g CD4, 0.002 KI, Anticalc - the only variable. 
There is only one standard formula for C41 developer. There is no acutance, 
or high sulfite, or high energy, or whatever equivalent. If you replace CD4 
with any other developing agent, you firstly get different kinetics due to 
different redox potential, different diffusion rate, different coupling 
rate, and the formed dye will have different spectral properties, like max 
absorbance shifted 10-15 nm, or more. Composition of C41, E6, RA4, is not 
secret, any skilled chemist with access to a lab and analytical equipment 
can reverse engineer it in one day. The real challenge is to investigate 
the emulsion, type and quantity of sensitizers, auxiliary stuff, 
crystalline forms, etc.


>Regards
>
>Tony Sleep
>http://www.halftone.co.uk - Online portfolio & exhibit; + film scanner info &
>comparisons




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