Bill, thanks for the reminder. I had forgotten that Mike wrote that chapter.

Michael, Crawley was both right and wrong. The older emulsions had buried iodide and were slower. They had little edge effects. The newer, double run emulsions, had surface iodide and thus had edge effects. In addition, modern or high speed emulsions have very efficient acutance dyes in them to aid in sharpness over and above the enhanced edge effects.

These effects are often difficult to see without the tests I described, except as enhanced sharpness.

The surface iodide seen in modern emulsions is also the reason why it is difficult to see enhanced sharpness with the older Crawley formulas which used iodide to enhance sharpness. These Crawley formulas relied on rapid adsorption of iodide on the grains surface and then release during development to cause mild edge effects.

You are in Montreal. This is not all that far from Rochester. Get a few APUT members together and then get GEH to lend us their classroom!

PE