I know, every scientist I work with uses "micron." "Micrometre" pegs you as a geek.
My question would be how important is this information anyway? Couldn't you get the answer from a simple densitometer? Not in terms of individual grain, which I think is not very useful, but simply the efficiency of the emulsion to pass/reflect light. You should then be able to scale to area? Perhaps not. Not sure.
Although, right now, I can't remember what the actual question was.
If I find an old B&W neg or print, I will put it under a microscope.
A micrometre is one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm, or about 0.000039 inches). The term micron and the symbol µ, representing the micrometre, were officially accepted between 1879 and 1967, but officially revoked by the ISI in 1967. It's still in use in some English speaking countries though.
I don't care what gear I have.
Things I sell: http://www.shutterstock.com/sets/413...html?rid=61105
From what I recall reading many years ago (and for me "recall" is a relative term for me personally...LOL)...B&W emulsion is on the order of 10 microns give or take, greatly depending on the film stock. Just as Bob (and others) estimated.
Shashin, very cool and yes, the whole world (especially the scientific community) works in metric . Just don't ask me why I have a couple of "english measurement" rulers in the draw next to me...LOL.