Thanks, that's exactly the type of feedback I was looking for! How would you say they are for going quickly between areas with a lot of tree cover and full sun (like biking/running)? Would a Prizm lens be more suitable for something like that?
I've used a pair of photochromic flak jackets for mountain biking in UK, WA and BC since about 2012 and am very happy with them. They are effectively fit and forget, put them on at the start of the ride and then let them adapt to the conditions.
I've got the clear to grey pair and they went plenty dark enough for August sunshine in whistler, but also go light enough for riding in the forest in UK winter.
Occasionally if it's really Bright in the sun and dark in the trees, I find myself thinking 'come on glasses, change already', but this is very rare.
The only issue is they don't change inside a car because the glass filters UV, so are useless for driving.