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Alex: October 2009 Archives

gs1.pngIf you've watched the weatherman on your local evening news, you know what a green-screen or blue-screen does.  The chroma keying process is the most popular way to extract talent or props from a moving image and composite them into another image -- like an animated weather map, or a virtual set.  Chroma keying allows your software to cleanly and automatically separate subjects from the background, while retaining their full range of detail.

Final Cut ships with a simple but powerful set of tools for pulling keys from green screen footage.  The keying tools in Final Cut Pro work based on the same engine as the tools in Motion, so you're free to work in whichever environment you're more comfortable with.

In today's article, a quick two-part guide to shooting reasonably good green screen footage and pulling the key in post.

Here's a short video tutorial on a creative way of using green screen.

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In a world of real-time editing and effects software, it's easier every day for new artists to do a great deal of work without really needing to render out their work in order to sufficiently preview it. Especially for After Effects artists who are coming from Premiere or Final Cut Pro, the idea behind the RAM Preview might not make complete sense. 

In today's article, two parts – the Backgrounder is for new AE artists, and the Tips section should be useful to everyone.

Backgrounder
rampreview-1.pngYou've no doubt noticed the little green "tape" above your timeline (pardon, "Time Bar") in After Effects.  In fact, if you're coming from other motion graphics or editing software, it's probably familiar: in most circumstances, it refers to portions of your project that are rendered.

The same is true in After Effects.  But in After Effects, you'll be seeing a whole lot more of the little green bar.  While editing software generally streams video straight from the disk to the screen, motion graphics software always represents your project as more of a "recipe card": the computer must manipulate the original video into an intermediate format.  This requires a substantial amount of extra processing power – quite often, it requires so much extra time that the computer can't maintain a real-time framerate during preview playback.  That's where RAM Previews come in.
For some reason, we seem to get a lot of people coming to the site looking to draw a heart beat.  I haven't the foggiest idea why, but I'm glad – it's one of those examples where Motion can make your life a lot easier.

This is what we're setting out to make today; you can dress it up however you'd like, and you can even use a shape that looks more like a "real" heartbeat than the one I drew.  We'll do a couple of approaches -- one is quick, the other is better-looking.
motion-logo.jpgAs you may have noticed, Apple has retired LiveType as of Final Cut Studio 3.  Fortunately for you LiveType folks, though, you can get to almost all of LiveType's functionality in Motion (plus a lot more).

Background

Our students really seem to like LiveType's LiveFonts -- sets of animated glyphs with which you could type as if they were a regular font.  In my grouchy opinion, the stock LiveFonts quickly grew stale as they began to appear all over the place, but even I have to acknowledge that there are some really nice third-party LiveFonts available, and many of my students have chosen to invest in those.

Motion can indeed use all of your LiveFonts, although it might not be immediately obvious.  If you're new from LiveType, you should first realize that the Inspector in Motion works very similarly to the Inspector in LiveType -- and all of the LiveFonts functionality is controlled there.  Motion's Library also contains thumbnail previews of all of the LiveFonts you have installed.

Read on for the Step by Step ...

motion-logo.jpgMotion's motion trackers are relatively sophisticated, as 2D trackers go.  In the general case, motion trackers can useful to give you a head start on basic compositing tasks like corner-pinning, to extrapolate simple camera motion to guide match-moves, and to extract elements of natural camera motion (see also the Stabilize Behavior).  And in Motion's case, its trackers are not only quite good at what they do, they're easy to use quickly.

To play with a basic motion tracker, load some kind of footage into Motion.  Then, apply an Analyze Motion behavior to it (Behaviors -> Motion Tracking -> Analyze Motion).  You should see something that looks like a circle with crosshairs:

trackers1.png

3dscopes-1.pngIn addition to the usual waveforms and vectorscopes, Color offers a 3D scope which scatters the pixels of your image through a 3D graph of the gamut of your selected color space.  It's great for "client wow factor," but I've still not found a student who can think of a really good practical use for the view.  Sure, you can roughly assess the distribution of pixels as you attempt to balance and guarantee consistency across shots -- but the freely-manipulable 3D perspective strikes me as too imprecise to use for much more than you could do with more normal scopes already.

The 3D scopes do offer one feature that almost all of my students agree is useful: if you click any of the three swatches at the bottom of the scope, you can pinpoint the values associated with one specific point in your image (by clicking and dragging on the Preview scope).  In the 3D scope, beside the swatch you have selected, you'll see text indicating the specific color values associated with that point in the color space you're viewing.  Even cooler (but probably less useful), the 3D scope will use bold lines to "triangulate" the selected point inside the mass of points in the 3D field.

In the remainder of today's article, I'll post quick snaps of the different color spaces represented in 3D -- but in the meantime, do you have any killer practical uses for the 3D scope itself?  Leave them in the comments -- the commenter who convinces me that they're uniquely useful on the regular will get a prize.
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This page is a archive of recent entries written by Alex in October 2009.

Alex: September 2009 is the previous archive.

Alex: November 2009 is the next archive.

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