06-02-2019 10:47 AM
I've had a problem with using AUTO ISO for videos using my Canon 5D IV. I've tried filming a clock for 10-20 minutes in constant photographic lighting condition using manual shutter speed (30) and aperture (2.8). I filmed the clock with both a Mark IV and a Mark III camera at the same time using the same settings. The clip captured by the Mark IV camera has shifting exposure (turned dark in the middle, and after 6 minutes, went back to normal again) and then shifted to dark again for a minute and then back to normal), whereas the clip captured by the Mark III camera has a constant exposure level. I had upgraded the firmware for the Mark IV camera and it still happened. I wonder why this is the case - have I done something wrong or is there a problem with my Mark IV camera?
Is it an analog clock? What camera AF mode are you using? What metering mode are you using for the video? Is there anything moving in the scene besides the hands on the clock?
I would manually focus a static shot like this. If the lighting will not be changing, then why not set ISO to a fixed value, too? I know that is a fix, and does not address the cause of the problem.
06-02-2019 12:01 PM
The clock is analogue. It's just a test before I do an interview. I did an interview two weeks ago and noticed this exposure issue and so decided to run a series of tests. The AF Method is Face Tracking and the problem occurred with both Movie Servo On and Off. Sorry I don't know about metering method. During one of the tests, I left the room and there was no other light source apart from the photographic lights and nothing else in the room would have moved. Then I sat in for another test and with the Mark III to make sure it was not the lights.
I'll need to do more interviews which involve a mixture of diffused natural light and photographic lights. That's why I wanted to try Auto ISO but after these tests, I would opt for fixed ISO but it would be useful to find out what exactly caused this behaviour of the Mark IV which did not happen with the Mark III. Perhaps the Auto ISO in the Mark IV is only useful for still photography?
If it is something to do with the metering method, would I be able to choose the method and how could I do that?