When you could be using 'contrastwise film bleaching' ...
Contrastwise film bleaching as explained by David Kachel et. al. involves bleaching the film after exposure and before development. It is achieved by using a very weak dilution of potassium ferricyanide which sounds highly toxic but I believe is not nearly so.
One simply immerses the film into the bleach with full agitation for a number of minutes. The result is a film response curve that is laid down to achieve a lower contrast ratio. I believe the process is entirely proportional to the amount of exposure. A slight loss of film speed should be countered during exposure.
As I understand it, a CI of between 0.4 and 0.5 is easily achieved. Thus a photograph with a more extreme SBR range can be accommodated for traditional printing methods with this process.
Similar outcomes can be had with divided developer techniques. Of particular interest is the Divided Pyrocat process which, by all accounts, produces wonderful results. Simply using Diafine is another well-known divided developer.
The difference is that the concentration of the Pyrocat in the Divided Pyrocat process is commonly 15:300 which is about 5 times what others use in a rotational process at 3:300. This makes the Divided Pyrocat process pretty expensive.
The other difference is also that a divided process is strictly a 'stand' process which is not possible with daylight tanks unless you want to completely fill a 3005 or 3006 for example !! More than a litre at 15:300 is extreme.
I suspect the answer to this question might be something to do with the range of results. For example, perhaps the contrastwise bleaching can't produce N-5 development as well as the Divided Pyrocat process ??
Cheers,
Steve
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