CRT TV Filming Motion Issue

[David Gordon]

I'm shooting a scene with 10+ CRT TVs in frame on digital without a global shutter. I ran some camera tests at 23.98fps, 144º shutter and found that the rolling line moved slowly up the screen on camera, but it was almost unnoticeable. However, on camera, I noticed that the motion on the TVs occasionally had a similar effect to dropped frames at certain points (the motion would seem to "lag" a noticeable amount). I confirmed that it was only happening on camera and not to the naked eye, so it wasn't an issue with playback itself.

Do you know what could be causing this issue with perceived movement on camera? Also, is there a way to fully eliminate the rolling line when shooting on digital with a rolling shutter camera, or is it something to live with?

Does anyone have general advice for shooting with multiple TVs at once (the same image on all of them) / things to look out for? Maybe models of TVs that might work best on camera (ideally 80s-themed)?

Thank you!

 

[Karim D. Ghantous]

This might help. TL;DR: you might have to set your camera at either 30fps or 29.97fps. A wider shutter angle is probably a good idea, too.

Edit: Can you not set a wider shutter angle than 144º on your camera?

(6:21)

 

[Howie Roll]

The bar is the blanking interval. It represents the 45 lines of ancillary data and blanking that are masked by the CRT bezel. When one captures a non sync’d frame the bar represent the delay between fields. At 144 degree shutter you’re going to see x amount of lines from field 1, the blanking interval, and x amount of lines from field 2. The darkness of the bar is a function of shutter speed and phosphor decay of the CRT.

I imagine the lost frame occurs when the blanking interval bar is correctly offscreen. Here is where you’d jump from field 1 to field 3 on the capture.

A 288 degree shutter may help mitigate both the darkness of the bar and the missing fields, but it may be a bit mushier.

Good Luck