Silly me, but here's my take on it:
If larger sensors 'gather more light', why is it they produce the same exposure as smaller sensors when the three settings of aperture, shutter speed and ISO are the same on both cameras? If there's a 'crop factor' for focal length equivalences, then there would be a corresponding 'exposure factor' between the two formats.
Full-frame: ISO 200, 1/60 sec, f/8 would require ISO 250, 1/30 sec f/5.6 for a crop. But since any triad produces identical exposures for both (given the same scene), then I guess 'full-frame gathers more light' doesn't stand up.
which is correct.
but..................
cover your entire body with SPF50 suntan lotion except for a micro 4/3 sensor sized patch and a 35mm patch.
expose them for the same amount of time in direct sunlight. Which patch is going to piss you off more the next day?
Think about it you've exposed
two different sized areas with the same amount of light, so it's kinda hard for the larger sensor not to gather more -- there's more area of coverage, so more light is captured.
Or I liked the sheet pan analogy before.
let's say it takes 1 cup of water to fill an 8x8" baking dish with 1/4" of water.
if you pour 1 cup of water in a 13x9" baking dish, can you still measure 1/4" of water?
If 1/4" of water is the equal exposure, then the larger pan/sensor needs more water/light in order to achieve the same exposure.
I'm still in the "who cares" crowd however.