an inexplicably intoxicating 2-minute slow-motion video of an espresso extraction
Just for my edumacation, was that shot starting to blonde at 1:22? The stream lightened slightly. Also at 1:24 there's a blonde patch (I think) just left of centre. Am I seeing incipient blonding or is that normal variation?
The shot is usually "stripy" coming out, just mixes together in the PF so without a naked, the contrast is not as pronounced. You don't cut just as it starts to change colour, but when it's changed colour and consistency.
Newer beans tend to produce a shot which looks lighter and foamier (thicker and more voluminious) from the star tdue to higher CO2 in the beans released during grinding and extraction. The darker stripes would probably be the coffee oils.