Photo Engineer
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There have been several posts here about the fact that Crawley's iodide addition method did little or nothing to some films and more to others. Since I know nothing about other manufacturers iodide content or positioning, I cannot comment. I did comment on the results from Kodak films.
It is known for example, that bromide addition to a given developer will change edge effects in the same manner. In fact, this has been reported on here on APUG years ago from someone using a dilute developer hoping that extreme exhaustion would give more edge effects, They got them plus fog and added bromide to improve fog, but instead got lower edge effects along with lower fog.
Bromide drag is an extreme example of this kind of effect.
All of these were studied years ago at EK and this is one reason that the E6 FD contains some iodide (as does the C41 CD). It is used to moderate edge effects with the high Iodide emulsions. In C41 in fact, it is there to allow the DIR coupler fragments mainly control the edge effects rather than Iodide as the PMT is more controllable.
PE
It is known for example, that bromide addition to a given developer will change edge effects in the same manner. In fact, this has been reported on here on APUG years ago from someone using a dilute developer hoping that extreme exhaustion would give more edge effects, They got them plus fog and added bromide to improve fog, but instead got lower edge effects along with lower fog.
Bromide drag is an extreme example of this kind of effect.
All of these were studied years ago at EK and this is one reason that the E6 FD contains some iodide (as does the C41 CD). It is used to moderate edge effects with the high Iodide emulsions. In C41 in fact, it is there to allow the DIR coupler fragments mainly control the edge effects rather than Iodide as the PMT is more controllable.
PE