s62, When I see cloudy triches that are beginning to bend over, I harvest. Ed Rosenthal says harvest when they start to turn cloudy with bulging heads, and that's what I do; I don't wait for them all to turn cloudy, because I don't want the THC to start degrading.
You should see that almost all the stigmas have turned brown and curled inward. You might still see some new stigmas emerging as the plant makes a last-ditch effort to get pollinated. But basically the buds stop changing, the aroma is intense, you can see lots of trichomes.