I’m about a week into a new Comedy series. We’ve taken the
foolhardy brave decision to shoot with a Canon 1Dmk4 and a 7D.
I already discovered an issue when using the cameras in low ISO and underexposed conditions with the “Highlight priority tone” function.
In testing I’d been please to see “Highlight Priority Tone” seemed to roll off the highlights in video in a more pleasing way. Sort of like the KNEE function on tape cameras.
Well after leaving it on and shooting an interior day scene at 200 ISO with highlight priority ON we found the dreaded banding artefacts were even more pronounced and that a sort of fixed pattern noise seemed to develop. It looked a lot like an improperly black balanced camera, something I’d seen especially with RED.
I guess it as perhaps because of the fact that cameras are constantly in “live view” so the sensors are getting toasty warm. The 7D has flashed the sensor overheat warning a few times as well.
But further research lead me to conclude that the fixed pattern artefact is induced when shooting at low ISO’s in underexposed conditions with Highlight Priority ON.
Once we turned it off and started shooting at moderate ISO’s such as 320 or 640, it basically disappeared and the banding seems to also have been greatly reduced.
It’s a shame because the function itself did seem to but me a little more headroom, but it seems at low ISO it trades off fixed pattern noise as well.