Random Colour temperature change in Raw

C

Colinelves

Well-known member
Has anyone experienced this:
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The apparent colour temperature of the image changes dramatically from one frame to the next. Shooting 4K Raw (in extreme low light). As I recall I think I saw this on the day but thought it was an issue with the Odyssey - which it may well be (not sure) but could be with the camera.

Looking at the waveform it seems to be a dramatic change in colour temperature rather than simply an increase in red noise (as the blue jumps as well) - so may be something odd going on with the gain levels in the camera.

It's Raw so largely correctable (not entirely) but it is a bit weird to have to deal with.
 
I don't think so - I never use auto anything, but I'm going to test today if changing the white balance could have caused this.
 
Colinelves said:
I don't think so - I never use auto anything, but I'm going to test today if changing the white balance could have caused this.
Click to expand...

There have been others having issues with extreme whitebalances.

Like 2000/2400K etc.

I cant remember what the concensus was however.
 
Okay. So I've been investigating this further in the office today. The issue is not due to me being a muppet and having auto white balance flipped or changing WB mid way through shot (although that was a reasonable assumption). Nor is the issue in the Odyssey as I can see it on the camera monitor as well.

As far as I can tell the 'bug' is a 'feature' of the camera*. It only happens when the the frame is significantly filled with an underexposed (and therefore very noisy) image (i.e. if there is a large enough patch of . To me it looks like the camera is adjusting the gain settings (reducing red and blue, increasing green) to reduce the noise and make itself more 'sensitive' in dark areas.

Notably it occurs in all 4K settings (24p, 30p, 60p, 25-, 50p) except 120fps burst. It also doesn't happen in 2K Raw in any frame rate (24,25,30,50,60+).

Also, notably, it is unaffected by black gamma settings (as you might expect given it's Raw) and running a black balance also doesn't stop it.

If anyone of you fine gentlemen (and ladies) could find the time to have a go to check if it happens with yours that would be ace as I'd like to see if it is just mine. It's pretty easy to do: Set your camera to 4K Raw - and close down the lens (or flip in the ND) so you can jump between a 'normal' exposure and one severely underexpose. You should see underexposed image suddenly become a little green.

Thanks!

*I was hoping to speak to someone at Sony Prime Support to try and confirm it is a feature not a bug (or my camera being damaged!, but they're answer machine is telling me the office is closed - despite the fact the recorded message also says it should be open: glad I don't have a major issue then!
 
sunnyjimfilms said:
I'm afraid I'm not seeing that change - temperature remains constant, as does values in RGB parade.
Click to expand...

Hey Sunnyjim,

thanks for checking. Can I just ask: how undercexposed did you go? It really has to drop quote low (maybe lower 20% on the waveform) to work with my camera.
 
I shoot a lot of 120fps and 240fps slowmo, internal recording AVCHD 28mbps 60p, ISO1600 or ISO 3200, and I see this *all the time*. I've seen the exact same thing on two different FS700's, so it isn't just a case that mine is broken, and I also always set manual WB, so I know that wasn't the issue.

Usually, in fact I think in every case where I've seen it, the background is dark, or black... in fact, checking further, it happens in very clip where the background is dark.

Colin - Interesting finding that it may be a "feature", not bug. I always assumed it was bad programming - much like the 1.5 second delay on starting 120fps slowmo when using "start trigger"... really bad programming there.
 
Interesting. Maybe conditions have to be a bit more specific. I couldn't see it in a low lit office. Will try again when I get mo.
 
Maybe don't try incremental - do a quick shift - e.g. flip in the ND. Or (as I did) expose for a window then move into the dark office interior.
 
Well it always seemed odd that black balance isn't available in RAW mode. Perhaps they implemented an auto blackbalance that is constantly working on the shadows to some degree.
 
Hmmm. Maybe. It's kind of crappy though. Just having a proper black balance would have been better. Also - it doesn't occur on frames that have a portion of highlight in - only in dark frames - in comparison a black balance would have helped everything, and not ended up poo pooing up shots when fighting for the light!
 
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