A7S Color Flicker

R

Ryan Lightbourn

Well-known member
Anyone experience a mild color flicker with their A7S? Almost as if there's some sort of auto white balance even when the camera is in full manual mode?

I've been seeing it pop up once or twice on every shoot day...weird green/blue flickering. I shoot ISO 3200 Slog 1/40 shutter, and a custom white balance.

Initially I thought it was from fluorescents or practicals on a dimmer switch, but I saw it subtly last night with a Lowel halogen kit and a practical/edison bulb (non-dimmer). I can upload a sample if necessary. I hope my camera isn't a dud. I also saw four brownish squares which looked like sensor pattern shenanigans in each corner of my frame last night. My A7S is starting to feel very BMPC-ish.
 
The splashes of color at the borders seem to be normal at high ISOs. I see purple blotches all the time on mine when shooting in the dark.
Do you also get flicker at 1/60s? 1/40 should be flicker free with 60hz mains but only if the electricity is very stable. Halogens can actually flicker even though they aren't discharge lights; the smaller the lamp power, the more likely it will flicker.
 
***EDIT: Never mind re: solved message (uploaded video to show the issue...maybe my camera is a dud)***

If you want to see what I'm talking about, set to Slog2 in "M" mode, point at a black object, look at the monitor and roll through shutter speeds or ISO settings. Watch the black object flicker from green to blue briefly after changing the setting (some sort of auto-correct). I infrequently see this while in record mode, but it does pop up from time to time (even with constant ISO/shutter settings).
 
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Seems like a rolling shutter artifact, possibly from a light source that is out of phase with your selected shutter.
Can you try this with a known working lamp such as am ARRI 650 at 24p50 at 1/50 shutter?
 
Haven't seen any color shifts of any kind. Strange colors- yes (not quite as strange as the FS700). Perhaps post an example where it's happening without changing settings? Maybe it's a bug? Have you opened camera and checked for a blue/green spider? ;)
 
bill totolo said:
Seems like a rolling shutter artifact, possibly from a light source that is out of phase with your selected shutter.
Can you try this with a known working lamp such as am ARRI 650 at 24p50 at 1/50 shutter?
Click to expand...

just tried it with the sun...same deal.

ill post an example later where it showed up on set and affected skin tones (same blue/green shift for a brief period while settings were constant)
 
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Ryan Lightbourn said:
just tried it with the sun...same deal.

ill post an example later where it showed up on set and affected skin tones (same blue/green shift for a brief period while settings were constant)
Click to expand...

Do you mean in the middle of a shoot it would flash blue/green? Do you have any examples of that. The door example, well my first thought would be a compression problem, because that iso change would force a complete frame update in the compressor. But i've not noticed this although i tend not to use SGamut much

cheers
Paul
 
paulcurtis said:
Do you mean in the middle of a shoot it would flash blue/green? Do you have any examples of that. The door example, well my first thought would be a compression problem, because that iso change would force a complete frame update in the compressor. But i've not noticed this although i tend not to use SGamut much

cheers
Paul
Click to expand...

I do have the example, sorry, haven't had time to upload it but I will later on today. It's the same effect...it just kicks in for a second or two. It gets sent out to ProRes too, so I don't think its a compression issue.
 
Here it is in a real world scenario with halogen lights (shouldn't have been a frequency issue).

https://vimeo.com/120326256
pass: a7s

Fun fact: when the old man looks up & laughs at the camera, it's because he ruined the take with a shart (so either way the take would have been ruined...but the flicker happened twice on this day & one of them ended up in the final product).
 
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Are you saying shart as in "****/fart" lol That guy is one creepy looking cat, damn I would love to use him for a horror flick, I love his look!
 
Can someone test the "M" mode blue/green flicker when scrolling through ISO or shutter? I'm still trying to figure out if I have a lemon.

Thanks in advance!
 
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