You need to get a microscope and check the trichomes.
It is impossible (regardless of what people my try to say) for us to know if a plant is ready from pictures, unless it is through a usb microscope. It is impossible for you to know if it is ready without looking at the trichomes through a scope. Any other way is a complete guessing game and you can be far off depending on strain. I have seen plants that looked past ready that were not and I have seen plants that appeared to have weeks to go that were past their peak.
The plant is ready when you are happy with it, and enjoy it most its a personal thing, perhaps like how folk like their eggs or how well a steak is cooked
best thing to do it take samples throughout the grow, from perhaps 7 weeks onward this hands on approach is much more fun
you can then decide when to harvest your plant via direct personal testing
personally i like calyx to fatten up hard before i harvest i like as much of a full bodied taste as possible
when you are sampling your bud you can look at it through your spy glass and pretend you are a scientist too if you wish
the only logical reason i can think of for letting the spy glass alone decide when to harvest, is if you are going to strip all the thc from the plant matter
and discard the plant matter, if you are going to smoke or consume the buds, then the consistency of the buds (plant matter/calyx /pistils) is of importance too
i do very much appreciate a good tasting bud, for me THC content is not the only important factor to consider
i would keep a good tasting strain over a more potent bad tasting one
i do not like beer that much, but i do prefer the medium alcohol content beer or export strength 5% vol
rather than the 9-10% strong beers
maybe folks that consume bud only for a medicine and not for pleasure do not care what it taste like, they only care about THC ?
each to their own
peace