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Replacing white sky.

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Jason FlorReplacing white sky.
by on Feb 21, 2015 at 1:53:43 am
Last Edited By Jason Flor on Feb 21, 2015 at 1:54:16 am

In the frame grab you can see a woman driving a car against a white sky. Note that the scene was shot with a Pro Mist filter which softens the edges. What is the best way to replace the white sky with blue taking into account the car is moving. I am using After Effects CS4. Thank you.

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Dave LaRondeRe: placing white sky.
by on Feb 21, 2015 at 4:54:28 am


Every sky replacement technique I've ever seen worked with foreground objects that had clearly-defined edges... which that filter got rid of.

The filter did another nasty thing, too -- it created just tons of light wrap. It's really blatant on the back of the subject's head. That's something that wouldn't even be there if it had been a blue sky with the sun shining on the subject. Simply putting in a blue sky would result in a shot that just screams, "FAKE!"

And speaking of the sun, it shines when the sky is blue. It casts shadows and it shines in a definite direction. But the lighting in that shot is flat. So as you replace the sky, you would have to pick a sun angle, then animate highlights and shadows.

All in all, that's one of the worst candidates for sky replacement I can think of. No, wait -- it could have been night, with a fog filter slapped on the lens.

Sorry to be the bearer of bad news, but if I were you, I'd start formulating a Plan B instead of trying a sky replacement. The prospect of devoting weeks to salvaging a poorly-shot image would be enough motivation for me.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA

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Jason FlorRe: placing white sky.
by on Feb 21, 2015 at 4:02:32 pm

Thanks Dave....I kind of suspected this would be the case but I thought I'd check with the experts before I gave up on the shot. The original footage was shot on a RED camera so I'll go back to RECINE X and try to do some more tweaking to bring the sky brightness down a few notches and lighten up the face. Unless anyone else has any other non sky replacement ideas.

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Tudor "Ted" JelescuRe: placing white sky.
by on Feb 23, 2015 at 2:04:31 pm

If the original footage is from a RED camera then you have plenty of color information to bring back details in the sky. Since you have clouds in the shot it will not be blue, but you'll get a lot of details. I would export a flat uncompressed sequence of files in a format that AE can work with (Open EXR, DPX...) and then do some grading work. Bring back the details in the sky using garbage masks and then tint the sky overall with blue. The final effect will be better than what you have now and you may get what you're after. I did this kind of grading on a spot shot on RED where the sky was supposed to be blue, however on the day of the shoot we had plenty of clouds. See example below

Tudor "Ted" Jelescu
Senior VFX Artist

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Jason FlorRe: placing white sky.
by on Feb 23, 2015 at 10:39:36 pm

That looks really good. I'll give it a try. thanks.

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