it's easy, you don't have to be a programmer
some detailed instructionsturn you camera on
set M mode
go to mem_spy settings in debug menu
set look for int16 (maybe int8), halshutter related on, range of adress 0x0 - 0x20 000, changes 20 - 300, other options should be turned off
turn mem_spy on
wait 10s and go to info screen (dont press halfshutter)
hold halfshutter until you find correct value
20x changes scene brightness
some variables will occur
look at the values in every third column how they react on scene brightness
if you have some suspicious, look at the exposure compensation and analyze what values have 0EV +1EV -1EV
if you will testing for long time some variables will hide, that's max 300 changes limit, in other word if you 300x changes you exposure our variable will hide (~ 2 changes in second on 5D2)
on 5D2 and 5D3


look at these images should get 1EV and your value 2049 or -1EV value 2047