Quick analysis of the gradient:
I took a regular picture at 1/4 seconds, and compared it to a silent picture, with shutter set to 1/8000. 5D2, no lens (totally defocused), ISO 100.
Script used for taking the pictures: dont-click-me.c
The test images: regular.CR2
(warning: large files)
Since the test images were taken from the same static scene, same ISO, same aperture, I should be able to plot the exposure difference and figure out the shutter speed from there, right?
So, I've loaded the two images in octave, and wrote this script for analysing them: gradient.m
Images in linear space, brightness scaled to fit the entire range (0-255):
Images in log space (EV), brightness scaled:
Image difference in log space (EV), brightness scaled:
Exposure difference per row, in EV (left) and linear (right):
Exposure range : 1/59.97 ... 1/3.86
Rolling shutter : 0.24 seconds
Not exactly ideal for moving subjects, even if we find a way to fix the gradient. But it could be interesting as a fast slit-scan mode.
You are welcome to run these scripts on more cameras, and post the results. I expect a little less rolling shutter from 5D3.
edit: this rolling shutter value was actually expected - in LiveView, Samuel H measured a rolling shutter of 25.9ms on 5D2
, and here it's reading out 9x as many pixels.