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Keying out and replacing sky

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Jamie Coote
Keying out and replacing sky
on Jan 21, 2014 at 3:16:59 am

Hey!
I have an extraordinarily detailed shot, you name it, it's there; trees, reflections, fine lines, etc. It was supposed to be sunrise but as winter would have it, there was little to see but grey flatness. Great, I'll just key that out, matte, luma etc... Or so I thought...
I've tried combinations of everything to swap it for a tracked still of golden loveliness, to no avail. Hence I'm here hunting for help.
I've stuck the proxy on youtube to show you all with what we are dealing (if it helps this was shot in raw). Apologies in advance, it was my first crane shoot!





Thanks in advance
=]
J


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mathew fuller
Re: Keying out and replacing sky
on Jan 21, 2014 at 3:24:05 am

The best thing to do in this case is to get a decent track first, get your sky moving as it should with the shot. Then multiply the layer ON TOP of your footage. You will need some rough mattes around buildings etc. But it will look great if (if done correctly) through all the trees, power lines etc.

~ Mat

Try the technique on a still image in photoshop first and you'll get what I mean.

My Work:
http://www.morecompletefx.com


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Jamie Coote
Re: Keying out and replacing sky
on Jan 21, 2014 at 3:35:45 am

Thanks for the speedy reply! The track is simple and I've got that working well, it's the areas around the tree branches and bridge that just look horrible. I just can't get the detail to come through. I can do it in PP because I can refine the sky selection perfectly but there isn't that dexterity in AE (or at least I dont know how) especially with the camera move as the selection changes so much.
Can you explain how you would matte to preserve the trees?
For the sky removal I've tried- Extract, Keylight and Luma key. For the Matte- Refine Hard/Soft and Choker. Whatever I do something spills over or looks mad and lumpy or mushy (technical words, I know). Nothing looks good and I can't face masking and key framing the whole thing as it'd take a lifetime with that bridge!


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mathew fuller
Re: Keying out and replacing sky
on Jan 21, 2014 at 3:39:43 am

Don't matte the trees. Just lay the sky right on top as a multiply layer. When you do it, you'll see what I mean.

You can also lay the sky on top (as stated above)...Then make a luma matte out of your original plate by crushing your levels so the sky is mainly white and everything else is black. then use that as a luma matte on your sky layer.

My Work:
http://www.morecompletefx.com


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Jamie Coote
Re: Keying out and replacing sky
on Jan 21, 2014 at 12:46:20 pm

Wow, that's looking a hell of a lot better. The multiply works a treat for the sky but darkens everything else quite a lot. Hence I tried the luma matte solution, just to check......
Layers are
1 - footage with blacks/whites crushed (layer invisible)
2 - Sky on multiply with layer 1 as its Luma track matte
3 - footage
This rectifies the darkness but causes that white featheriness around the tree.
What am I doing wrong?


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Chris Wright
Re: Keying out and replacing sky
on Jan 21, 2014 at 2:33:14 pm

aecs5.5 test sky

here's what i got in 2 minutes

ae cs5.5 sky with 3 luma mattes
7029_skycs5.5.aep.zip


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Jamie Coote
Re: Keying out and replacing sky
on Jan 21, 2014 at 3:55:34 pm

Thanks so much for this! I wish I could see how good it looked but I can't work out where to put the actual footage amongst your layers?!
Sorry for the noobness!


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Dave LaRonde
Re: Keying out and replacing sky
on Jan 21, 2014 at 6:01:39 pm
Last Edited By Dave LaRonde on Jan 21, 2014 at 6:12:13 pm

A bit of hard-won advice.....

When doing effects work -- which is what the shot turned out to be -- you should always KNOW that the techniques you propose to use are certain to work before you do it for real.

This knowledge comes one of two ways: experience and performing tests. So if you don't have the experience, do the testing.

The phrase, "we can fix it in post" is almost always shorthand for the phrase, "Let's shoot it now anyway. Let's not worry about the massive amounts of extra time and money it will cost us later to fix it."

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


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Chris Wright
Re: Keying out and replacing sky
on Jan 21, 2014 at 11:40:44 pm

just right click replace sky.png with sky video. and you might need to resize the comps and sub layers to your video size.

here's another way how to do it and it also shows tracking techniques.
http://library.creativecow.net/articles/kramer_andrew/sky_replacement.php


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Jamie Coote
Re: Keying out and replacing sky
on Jan 22, 2014 at 7:29:52 pm

Thanks again Chris, I'm super grateful and it worked flawlessly!
Just one last question! How can I choke the white feathering around some of the edges (though it only really shows up if I use a crazy colour for the sky)?
And if you ever need a DOP in Paris or London, I'd happily be your man.


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Chris Wright
Re: Keying out and replacing sky
on Jan 23, 2014 at 12:25:32 am

you'd just have to play with the settings.

try turning off the matte chokers in mask precomp,
rgb pro tolerance 0
hue protect whites tolerance 0


in final blur comp,
in final blur mask layer before channel blur, add a level-individual controls effect set as alpha input white 2.0. that will clamp on the branches


doing all this definately removes branches problem but you might have to garbage matte buildings more if they have white windows. that's what matte chokers are for. So its a trade off. Speed for accuracy.


Happy Tweaking:)


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