Under the microscope the trichomes appeared less "cloudy" than when I looked at them with a hand-held loupe under the growlights, so this could be tricky. My grower-friend who was over a few days ago said it's hard to get all the buds to have the same degree of maturation, so you have to go on an individual basis. He said his rule of thumb was to pick when the bud had mostly cloudy trichomes, with an equal amount of both clear and amber/black. But Rosenthal says it's a bit of a user preference because you're really selecting for THC vs CDBs, with the latter being present in the cloudies, the former enriched in the clears.