Here's an idea. I haven't tried it yet, but it may give a good starting point: Set up your camera outside on a tripod and lock it off. Take a few seconds of footage during the day with the apprpriate aperture, exposure, gain settings. Then wait for it to get dark. Take a few more seconds of footage with new aperture/exposure/gain. Get stills of each and try to make the day shot look like the night shot. Notes: The night shot will likely be grainy, due to the increased gain needed in the camera, but it should still give a good reference. If anyone does this, let me know how it goes. I may try it soon myself.