Digital BW, The Print

fredfischer77 wrote:
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Bruce Watson <bwyg@...> wrote:
> Hi Bruce
>
> I believe grainier highlights are a product of development. Highlight areas tend to exhaust or have slower development activity, because of the large amount of exposure they receive, creating a larger "grain" where as shadow areas develop more fully. This really holds true 
> with "silver solvent" developers like D76.
>   

Interesting theory which holds some truth if you are talking about stand 
or semi-stand development where the point is to induce developer 
exhaustion in the highlights. For normal agitation however development 
doesn't exhaust anywhere on the film. That is actually the point of 
normal agitation -- to prevent developer exhaustion.

Grain clumps vary widely in size depending on exposure and subsequent 
development. One of the reasons for this is the 3D nature of the 
emulsion. More exposure means that photons transit deeper into the 
emulsion. When developed to metallic silver, the individual grains 
overlap forming a larger overall grain clump. If you want to see some 
photomicrograms, have a look here:

http://aic.stanford.edu/sg/emg/library/pdf/vitale/2006-03-vitale-filmgrain_resolution.pdf

Mr. Vitale has been researching this and other film topics for decades. 
There's way more information here than most people want to know. But it 
all makes sense, and other researchers like Kodak's Grant Haist back him 
up.

I specifically refer you to page 17, figure 18-D which shows an 
excellent example of grain clumping.
--
Bruce Watson