2 ways to tell ripeness:
One is to check the trichomes with a 40 x power magnifier/microscope.
But thereare differing opinions as to how to interpert what you see.
Some say harvest as soon as the trichomes change from milky to amber, others say harvest when they are 50/50.
Then there's the "old school" way: harvest when 75 % of the bud hairs (no magnification needed) change from clear/milky to red/brown.
Both those methods are used to determine the max. THC.
But there are other psycho-active compounds contained in marijuana besides THC. All contribute to the high.
I find that with indica/i-dom's, I like the high obtained by harvesting a little early (say 40%--50%) just as much as waiting until 75% color change has occured. The earlier harvested pot produces more of an "up" high, as opposed to the couchlock stone of later harvested buds.