Color Matching and Foreground Replacement Question

[jdkhanlian]

I am trying to replace the foreground in a shot. I am compositing a layer in the bottom third of the screen on top of a shot which has the sun rising. I'm having trouble matching the look of the composited shot to the shot underneath, since the shot underneath changes color and light spills out over the entire frame. I'm wondering if anybody has some ideas of a good approach to match the color and the light spill. Thanks!

http://vimeo.com/69057519

(The first shot is without the composite, and the second shot is with the composite that needs work.)

 

[starcentral]

I just did a composite separating a foreground from the background so each scene element could be treated separately with color correction and some lighting effects. After we decided to scrap a "clear night sky" and go for a cloudy night look with a moon. The shot was done "day for night" and also the entire 20 second scene opens up with pan from the left on a jib arm slowly raising up. It's still a work in progress but you get the idea:

I think some of the techniques I used would be similar to what you are trying to achieve.

First, for what you're trying to do the sun glow and sun flare can not be removed from the original shot so that it could be added to your replaced foreground. That's because it's really more like a layer that is going on top of everything with some transparency. Sure you could probably fake a new orange/yellow layer on top of your entire comp and make it look like the sun extends over your new foreground element but it may or may not work or look real.

Here's how I'd pull off your effect:
- I would shoot a new time-lapse plate of just the sun in the sky completely separately without the city in it.

- Then I would shoot your city scape without the sun in the shot at all. It could be anytime of day as long as the sun is not in the background or shadows don't reveal the "real" direction of the sun.

- In AE take your city scape and new foreground element and work at making them match perfectly. I would use that darker tree line from the city shot as the point to match up the background and foreground. You need to create a mask on your foreground that is more rounded like the tops of the trees and feather it so there is no hard edge. Also apply "curves" to the foreground layer and with that adjust your overall brightness/contrast and even move your RGB channels around until you can get the trees to match up better in color and contrast.

- Pre-compose these two layers into a new composition so they are combined as one. This is now your new foreground layer.

- Back to your main comp (not the new pre-comp one) you can create a mask now so that any layers underneath this one appear in the background of your composition. The mask needs to be pretty accurate. You will use this mask so you can get your sun plate shot to appear as if its behind the buildings rising. In my project I actually used the roto-brush tool to create a mask around the bushes, barn and tree line, and it does a pretty good job at doing the masking for you. (One caution about the roto-brush tool as that as soon as you make any change to this layer the roto-brush needs to propogate - depending on your machine it can slow it down and you have to wait for the propagation to finish before you can keep working on your AE Project, well its pretty annoying)

- Drag your sun shot to the bottom layer of your comp and you'll have your sun rising shot behind your buildings. (similar to how I was able to create a "glow" from behind the barn in #2 of my pic). Its a good idea to scale up this layer so you can actually position it where you want without having to run out of your background.

- You have some further sky options. For example turn off your sun rise layer for a second and drag some sky video or image to the bottom layer. With some new sky, you can turn your sun rise layer back on and try some of the screen transfer modes like screen, multiply and see how it blends.

- The last part of the effect here is to animate a lens flare and possibly a light yellow/white circular wash that starts to become apparent as the sun comes more into the shot. You can keyframe the opacity of a layer on top of all your layers and even motion track it to move a bit with the sun.

 

[paulcurtis]

I assume that's the only footage you have to work with?

In addition to what Dennis says:

Your main issue is adding the sun flare over your comp and to do that you need to have the flare by itself. There appears to be some frames from your source without the flare and with the flare. If you subtract the first frame of the background (no flare) from all the other frames you'd be left with just the light from the sun flare which you can blur, denoise and add over your own foreground comp.

hope that helps (a little)

cheers
Paul