T354 Week 12
- Spring 2015
- Your final project
proposals are due next week.
- Bring your book to class Thursday. You'll need it to run through a lesson on multipart tracking.
- Review work
- Motion tracking (continued)
- Final Project proposas due next week
Keying in AE
There are some bluescreen files you can use in this 70 MB zip file:
- Blue Dance
- blue screen.mov
In the AE pro bundle you will find several
different types of color keys. Many good keyers are made by 3rd party companies (Ultimatte, Keylight, Boris, etc.). An
excellent one (Keylight has been built into the CS3 release of AE.
it is possible to get good keying out of AE's built-in keying tools-
but the footage should be lit well and recorded into a codec with good
Review color sampling (4:1:1, 4:2:2) and need for evenly lit blue/green screen footage. Note the different codecs in Blue Dance (DV) and blue screen.mov (Animation).
Garbage matte (aka junk matte) - Often when subjects are shot
for chroma keying, there are areas not masked or covered by
the blue or green screen material or paint. These are typically
outside of the subject's area of motion. Because they aren't
the uniform blue or green required for color keying, we use
what's called a garbage matte to get rid of them. In AE it's
easy to use the pen tool to make a mask that serves as a garbage
This is the basic color keyer in AE. It can work well if the footage
was created in a 3D program with a highly uniform color background.
While it works well with really uniform color keying, it's hard to
get some bluescreen footage to work, as it's not extremely uniform.
A little edge feather can conceal bad footage or lighting but will
lose the fine details.
Luma keys work on brightness (as opposed to color). They are good
if shooting against a solid white or black background.
Linear Color Key
This is a more sophisticated and easy to use color
keyer with the interesting feature: you can use the + eyedropper tool to add to your matte or the - eyedropper tool to subtract multple times.
The matte choler and simple choker let you modify the matte created
by the key. This is a quick and dirty way to eliminate the fringing
Color Difference Key
This key will get you much closer,
as its additive eyedropper tool allows you to more easily create a
good matte. It might be overwhelming for those new to keying.
This is frequently used for video work.
It is simple to use and has additive and subtractive eyedropper tools.
A difference matte compares one layer
to another and then keys out the info that's "different." This
is usually used with footage shot from stationary cameras, or from
motion controlled (repeatable) rigs. Imagine you have two layers, one
is a static shot of a room. Another layer has the same shot, but a
subject walks in. Using a Difference Matte, we can key out the subject.
This is an excellent keyer provided with AE. Check out the links below for additional tutorials on how to use it and make better mattes.
Any good keyer will allow you to examine the matte. Ideally you want to adjust the settings until you get only black and white (what's keyed out and what remains visible).
Note that with all of the keyers, you will likely need to add an effect
to get rid of an unwanted color fringe. The maniuplating the Hue /
Saturation helps. You can use AE's spill supresser and the simple choker
to clean up nasty edges.
Additional Keying Help:
Check out the on-line help, the book, or these tutorials:
There are several bluescreen clips listed above. Use the keying tools and the info in the tutorial to put any of these clips
together against any background you choose. (E.g. you could have the dancers dancing on the moon.) Can you add a shadow to make it more realistic?
Leave a full-sized, square pixel movie
(H.264) in your week 12 folder. Make
sure it's called "bluescreen".
Exercise (5 points)
In this exercise, you'll show you can track an object, even though
it moves out of the frame. You'll need 1 piece of media from the Meyer DVD:
This was in the video files which were in last week's lecture notes.
- Follow the instructions in the Multipart Track tutorial (on page 511 from Chapter 30)
- Make a 4x3 DV-sized comp to place the LS_hihat_snare.mov in
- Look at the video. The goal is to create three different elements, which will be tracked along with the camera movement. The first element will appear in the green area underneath the hi-hat. It will follow/track the hi-hat as it moves up, out of the frame. Another element will track up, along with and over the white drum head (using the white drum head as a background). The third element will track down, again in the green space following the camera move. These elements could be text, or anything else you want.
- Make a null layer to apply the track to
- Track the movement of the
LS_hihat_snare video. (The trick is to hold the "option" key to move
the search and track square to another part of the video as needed.)
- Only use the Y (up and down) axis before applying to the Null layer
- Use the Smoother (Found under the "Window" menu to smooth out the bumps a bit.
- Make 2 separate elements to tie to the motion (1 for the camera tilting down, the other for the camera tilting up)
- Parent these to the Null layer
- Adjust for a pleasing look
- When you are finished, render out a full-size (H.264) version in your week 12 folder.
- Make sure it's called "multipart"
Be sure you know about these resrouces:
If time allows - show Shape Layers
- Read & work through Meyer, Chapter 32 (Shape Layers)
- Make a 15 or 30 second fake (or real) ad. It must have:
- at least two animated Shape Layers (read the book!)
- a layer that is motion tracked to another
- Turn in a square pixel H.264 version.
sure to note what you did and how you carried out the motion tracking in the accompanying
- Upload your finalized Final Project Proposal to the Oncourse/Resources/Final Project folder.
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