Me neither but my understanding, from the podcast with the Chameleon reseracher (I forgot his name, I'll find the podcast later, painting right now, just taking a break

.). That Chameleons are always hunting, never laying around.
They don't get food on a plate like they do in captivity.
That all said, shade in the wild is 50k lux, a T5 UVB and a 75w basking light is 6k lux at the screen. There is a huge difference between those.
And like I said, light differs for a rainforest Cham, then a panther or veiled. Panthers in the wild are found alot by the sides of roads on dead branches of liana's, there is no shade there. There is no leaves, just dead branches.
I would go and take a look of some of the climate pics on Madcham.de, for Panthers (I don't know if they have Veilieds) they don't live in a rainforest. There environment is much closer to a desert. It's still wet, it isn't a desert, but it isn't what most keepers design there cages to resemble either.
I was suprised, when I looked more in depth as well, when James pointed it out to me.
And as far as montanes they stay in the undergrowth areas, but the sun is still bright there as well, the trees are mostly palms in that area, or palm like, they don't block the amount of light people think they do.
They are not hiding from the light in your example, they are hiding from the heat, they are thermoregulating to a cooler part of the cage.
If you look at pics of alot of montanes where keeps don't use basking lights, they stay in the light a good part of the day.
Then there is also, of course personalities, so chams could prefer low light, others prefer high light.
Also in humans, (I don't think there has been study's done on reptiles) low light levels make us tired, and not want to do anything, where bright lights increase productivity and energy, that is why office buildings are lit so brightly.
Chameleons also use the brightness of light, to tell time and season, and they adjust their behaviors accordingly to the amount of UV light, the brightness of light, ect. Low lights could be putting them a in a restful, winter state. Where they feel the need to sleep and relax, instead of be active and hunt.
This is a great read on it. With 1 correction, it's an old article, and we can recreate the sun much much better than back then, by using LEDs and computerizied controllers. We can adjust for time of day, and season, with relative ease now. If you went that extreme, in a cage built for the purpose, would could even recreate the sun's movement across the sky. We can even program storm's, that are accompanied not just misting, but lighting lowering and simulating clouds, ect.
ntp
://www.reptilesmagazine.com/Reptile-Health/Habitats-Care/Reptile-Lighting-Information/
And to be clear, I am not bashing anyone for useing the tried and true, old school approach. It's exactly that, tried and true, easy, accessible, and fairly inexpensive. However that doesn't mean we should be afraid of moving forward either. Or trying to improve.