Originally Posted by Philip_L
Possibly not, if you expose for the sky, then the darker areas would become under exposed and very dark or black. This is where dynamic range kicks in, the camera can only capture a limited extreme of dark or bright with the same exposure setting. Something has to go out of range when you have very bright and dark areas in the picture.
Remapping values above 235 gets a bit more dynamic range, but even then that may not always help.
The professional way is to use a graduated ND filter, this filter is shaded at the top and clear towards the bottom (similar to half tinted sunglasses), so the sky is darkened and bringing it into range to allow the whole frame to be captured without blowing the highlights. You often see this on some lower budget TV programs or news reports where they've added a graduated ND filter but then decide they need to pan. The shaded area becomes visible as the picture changes.
Sometimes you need a matte box to make these sorts of graduated filters work well, and they only work on shots where the frame is split cleanly across the horizontal so sky at the top and landscape at the bottom. It has to be a steady or a tripod shot as movement will make the filter become visible as the line between shaded and unshaded will not move with the image.
Other ways are to brighten the subject or the shadows using reflectors and/or lighting.
However these techniques don't lend themselves to our domestic use of camcorders, so it is case of avoiding such scenes, letting the highlights blow out, or dealing with in post.
An ordinary ND filter will not help as the whole frame is affected, the sky becomes less dark, but the shadows become darker so you still have the same difference between light and dark.
Another option that can help with blue sky at certain times of the day is a polarising filter, as this will darken the sky without darkening other parts of the image, helping to stop the sky being blown out.
Originally Posted by Ken Ross
Since we all look at videos with different monitors, many of them totally uncalibrated, it's difficult to see exactly what you're seeing.
With that said, if you scrub to that portion of the video, you can easily see how the sky changes color as he changes exposure. At the beginning of that clip, before he lowered the exposure, there was nothing odd looking about the sky on my monitor. In fact, I might have left the exposure right there. There also appeared to be a slight haze which can alter the color of both sky and objects. That happens in still photography as well. Once he reduced the exposure, the scene looked a bit 'off' in terms of color, not just the sky.
I don't believe this is a limitation of RGB values or superwhites at all. As I said, on my monitor the beginning of that clip looked fine. Only the person shooting can tell us if it was truly 'accurate'
Edit: Didn't see your screengrab, just the video. I thought you were referencing the castle shot.
So for that shot a better compromise could probably have been established with a lesser exposure. Not sure if the sky would have been totally natural given the stark contrast, but it could have been improved, I'd suspect. As with any shot, you have to determine what the subject of the clip is. If the sky is important to the scene, than either expose for that or seek a compromise. In short, you work with the dynamic range that the camera you're using offers.
Phil and Ken,
Thank you very much for your valuable feedbacks to my questions.
Again, my intention was to learn what was causing the sky "discoloration" and how to possibly control it or even better avoid it.
It was not meant to be critical of equipment or video itself.
May I also add, that the reason, I have focused on the sky in that part of the video, is that my own camcorder Panasonic SD600 is driving me sometimes crazy with incorrect color and not necessarily "bondi" blue issues.
I have found out that it helps a lot (with my camcorder) in some situation, like filming a beach scene, to first focus on the beach sand or rocks and then slowly move towards the water (sea/ocean).
Another example of a really challenging situation I noticed recently, while watching FIFA World Cup Soccer games, was when the field/grass was partially in the shade, while the rest of the field was in the sun. Even professional broadcast camera had difficulty with the exposure, as the shaded part of the field was to dark on the television screen.