Adv Post Week 7: Sin City

Keying : selecting part of an image to keep or remove, based on color

Tracking: following the mov't of something on-screen, with another thing. (based on movement)

SinCity: Selective color keying.
Selecting 1 color to keep, and all the rest will be black and white.

1-Matte: everything black except for our color element, which will be white.
-White is our window. Anything white will stay, anything black will go (will show thru to the next layer. Window thru which the colour looks.
2-Colour layer: Enhanced version of our original.
3-BlackAndWhite copy: original with no color.
As if shot on black and white stock.

To use this technique for selective Color Keying instead,
1-Matte: just brightest part of frame, in black-and-white high contrast
2-Darkened/Color-corrected version of original
3-Original

Drag your footage to project window
Drag that from there to comp icon to make a new comp
Isolate the section from 6:04-9:00
6:04 hit B
9:00 hit N
Rt-click the work area, choose "Trim"

Duplicate 2x
(apple D)
rename by hitting Return
-Matte
-Colour
-Black and white

Change the BlackAndWhite layer by turning the other eyeballs off and then applying Hue/Saturation.
-Reduce the Saturation to -100
-Optional: apply Levels effect to increase Contrast

Change the Colour layer by adding the effect Hue/Saturation (and swirling the Hue wheel) or applying Change to Color. Set an original color (green) set an new color (purple), and adjust the controls

Fix up the Matte layer, by applying Linear color key
-Key color is the most important thing
-Pick a mid-range color, not a shadow or a highlight.
-Reduce the Softness value to 5% or so, it always starts off too high.
-Increase the Tolerance: this selects more pixels to key out.
-For finer control, hold the Apple key down while scrubbing a value.
-Changed the View option on the Linear Color key to "Matte Only"
-Apply the Levels effect, slide the white slider toward the black to incr contrast.
-Apply the effect "Invert"
-Change the TrkMat to Luma

If you didn't get enough color selected,

Apply Linear Color Key twice, but instead of View/Matte Only, choose "Final output" on both

Apply the Effect "Invert Alpha"
Apply the effect Shift Channels
Alpha=full on
Red=Alpha
Green=Alpha
Blue=Alpha

And now you have your matte.