Originally Posted by Ken Ross
But we do know that Panasonic has had some significant color issues that the Canons have not had.
Which doesn't ever seem to show up in reviews no matter how technical, it's a strange one.
Personally I think many examples of bondi-blue skies are simply over-exposure, this youtube
clip demonstrates it very well. Freeze it at around 17 seconds where the brighter part of the sky starts getting a green hue as the person starts deliberately over exposing.
Take a screen shot, dump it into a paint program and sample the colours at around 17 seconds.
All that is happening is blue sky contains a lot of blue, a good chunk of green but very little red. On over exposing once blue reaches 255 it can't go any higher, it is clipped, so the blue channel is overexposed, but as exposure continues upwards, the green and red channels continue to register more as they have some head room. Eventually green clips at 255, but with there being less red in sky that takes a lot more to over-expose.
At around 17 seconds if you sample the sky towards the left/middle, you will find RGB values of Blue 255, Green 255 and Red around 200. With blue and green at 255 that shows overexposure and clipping, what the camera is really seeing is perhaps blue at 400, green at 300 and red at 200, but can only register 255 maximum.
Mix the clipped RGB values with the not yet overexposed lower Red value and what do you get? Towards the right at the same 17 seconds the sky is brighter and over-exposed more and we get red clipping also, so essentially white sky, which no one thinks to complain about. At around 20 seconds into the clip it is over exposed even more, so we get the darker sky taking on the bondi-blue and if you sample you can see blue is clipped at 255 over what was blue sky, so the colours are now skewing towards green.
If this were a single chip camcorder with interpolation, I expect you get this scenario much less often due to the way colour is derived by taking averages of surrounding pixels so as one channel starts to clip and over expose that pushes the others towards over exposure much quicker.
Watching various TV programs, I've seen similar bondi-blue skies popping up from time to time. I expect many more are tweaked afterwards.
It is basically the cameras ability to process colours separately that shows up how overexposure is effecting colours. It might explain why one report which I think I read here reported using the extended colour space to a TV that supported it showed blue sky, yet it was green on the computer. The extended colour space meant blue and green were not over-exposed and could be recorded correctly, but were clipped on a computer that didn't support that extended colour space.
I suspect if you sample all cases of bondi-blue skies and test the blue, they will probably all show blue as clipped at 255. Once blue is over-exposed, the colour can only skew. That isn't a fault with the camera, it's just how these things work and why we have things like graduate filters etc.