A7s Weird Rainbow Rolling Flicker in 720p120

J

jb.

Veteran
I'm getting a weird rainbow (RGB) rolling flicker at times with my test footage for 720p120 on the A7s.

Shot in 720p120 XAVC-S 50Mbps, f/1.4, 1/250th shutter (does it with 1/125th shutter too) imported into Premiere CC 2014 and duration adjusted from 120fps down to 24fps (20% slow-mo).

Here's what it should look like:

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Here's what the flicker looks like as a screen grab:

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It comes and goes, definitely not there all the time. It also doesn't seem to be present when played back on the camera LCD as far as I can tell, so maybe it's an encoding/decoding issue?
 
What lights are you using? Fluorescent? Looks like it could be flicker from fluorescents/leds due to the high shutter speed. When viewing on camera, are you viewing slowed down to 24p or is it full speed? Many flicker issues will only be visible when you view video slowed down so that you can see every frame. If it records full speed material, and you play back at normal speed, you may not be seeing all the frames or the particular speed of playback hides the flicker so the flicker may not be visible. That happens to me all the time on the FS700 in 240fps, I record a clip and while it buffers it out it shows the 240fps clip played back at 60p while it writes to the card and still no flicker is visible, but the flicker can be very bad when viewed at the final 24p speed.

Try shooting in sunlight. If you still get flicker, there is something very wrong.
 
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Definitely not fluorescent bulbs. That should have been natural light (there aren't any lights on in my office right now).
 
jbregar said:
Definitely not fluorescent bulbs. That should have been natural light (there aren't any lights on in my office right now).
Click to expand...

Are you sure? Then something is very wrong... Does the camera have a black balance option?
 
I just shot something else in a separate part of the house and it didn't do it... maybe it was something odd between the lens adapter I'm using and the way the light was coming into the room.
 
it almost looks like the camera is trying to white balance the forward part of the image where the blades move through. I would see if you can replicate it again in the same shot, then change WB options to see if you can still replicate it.
 
that is light flickering, it will happen with any camera recording at that fps with that shutter speed
use different lights

(if it happens in sunlight too, then I'm wrong and it is something else)
 
I've had a strange issue like this happen to me on two separate occasions, and shooting in 24p. I was using tungsten bulbs, so it wasn't an issue of flicker. Was your camera hot? Both times it happened to me, it was toward the end of long shoot days.

EDIT: Mine may not have been so much rainbow, but almost like a varying auto-white balance look
 
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