Sky Replacement Help

[eraserhead_in_time]

Hey guys,
I have few footage from which I wanna replace the sky to create a more dramatic scene.
I use CS5 and am trying to understand rotobrush fully. Heres the problem
The horizon has few trees in the background that also needs removal...

When I treey rotobrush, sky gets selected easily but those trees have zillion holes between leaves showing sky behind which is impossible to select...

When I tried Andrew Kramer's method of Inverting Luma matte, the trees remain intact...

I'm thinking of masking using pen tool but that seems awful lot of work if i have to keyframe their position every next frame...


Is their a way that im not seeing???


Kindly help

Thanks

 

[PaulGriffith]

You'll probably have to hand-rotoscope the horizon out of there. Rotobrush is for big-fairly simple shapes and the video copilot sky replacement tutorial is for just that, sky replacement.

Hollywood vfx companies still spend a chunk of time rotoscoping. It's the norm.

 

[eraserhead_in_time]

thanks for the reply paul
and darn!!

 

[wheatgrinder]

seems you can still track your shot and simply mask once and have the mask STICK to the the frame.. yes?

 

[chilipie]

I'm not sure if you need to animate the mask because the shot's moving or because the trees are blowing in the wind? If it's the former, then just do as wheat suggested and motion track the shot to make the mask stick to the trees. Roto brush is really useful, but I've always had to go and tweak things by hand afterwards.

 

[Anim8]

Been there, done that.... If its a moving shot, simply tracking the shot for the mask rarely works because the trees have so much dimension. The branches will change constantly if you can see through them.
Something that I have done before:
Duplicate the background clip and use a gradient mask that starts at the lowest piece of sky showing through the trees. Adjust the color of the sky until its similar to your replacement sky. Add the replacement sky layer behind your masked clip.

This way you can gradually fade into a replacement sky and not worry about having to roto the trees. But all of these ideas will depend on the source footage.....

Good luck!

 

[knightly]

ND Grad! Tight gradient transition using the luma change as a border. It won't be a replacement, but it'll darken the sky a bit for you (I would actually let the trees darken slightly at the edges rather than the the sky stay bright at the fringe... it'll look less halo-ey.

You could also use that technique to make a mask for the sky.

 

[wheatgrinder]

seems the OP wants to remove the trees too.. so it not TECHNICALLY just sky replacement. It more truly a set extension.

EDIT: Or is the OP saying that he wants the trees removed, because he could not get the sky to replace correctly BEHIND the trees..? Big diff.

And Kniqhtly is right.. just ND filter from the horizon up into your NEW sky.. thats the way it looks normally in the real world anyway.

OP.. post a screen shot.. ??