3x crop, readout speed/technique

[roisinmurphy]

i did some useless quick rolling.shutter tests on my 5d.mark3...

and the rolling shutter on the 3x crop, is the same

so i assume, magic lantern cannot just quickly read out the 1920x1080 pixels in the middle, it still has to wait for the whole sensor read.out, and then just records the crop, instead of binning the pixels?