Understanding Masks, Mattes, Alpha Channels

[Chris Smith]

If you haven’t bought the books “Creating Motion Graphics” and “After Effects in Production” by Trish and Chris Meyer, you are doing yourself a huge disservice. They will get you way up to speed.

In general:

A matte is any greyscale image that defines the opacity of an image on a pixel by pixel basis.
An Alpha channel is a convenient 4th color channel that is embedded in some file formats and is a fundamental part of the video stream internally in any compositing program that defines the transparency. Basically it can be called the “matte channel”

A mask is AE’s name for a shape that can be drawn on screen. That in many cases is used to define alpha channels. Obviously these shapes can be used in different ways. They can be blended, subtracted, intersected, etc.. They are one of a compositors tools to create mattes. Other tools are keyers (like when doing a greenscreen or luma key), paint brushes, or other images that contribute their RGB channels as luminance mattes for other layers (like when using a luma track matte in AE).

Chris Smith
https://www.sugarfilmproduction.com

[Joeythedog]

Well, alrighty then.

So, I go to photoshop and I make 2 new graphics. one zig zags and one poka dots. I make them consisting of 3 layers. A solid background, a copy of the background with the dots or zigs, and the third layer the dots or zigs on a transparent background. Ok two graphics one dots and one zig zags. I also go into channels, and with the dots or zigs selected, create an alpha channel. I save both artworks as varing amounts of layers from flattend thru the 3 layers with an alpha channel.

I load all sorts on combinations of layers, alphas, into AE and not only that I change the interpert footage settings- i.e. ignore, straight umatted,
and premultiplied-matted with color.

Also, under modes I checked and unchecked the T transparency and inverted and also worked with the TrkMat.. Track Matte settings.

I now understand why I did not have a grasp on Masks, Mattes, Alpha Channels. Billions & billions (god bless Carl Sagan) of combinations. Man talk about complexity. When a person fully has a grasp of all of the effects available along with modes “silhouette alpha” (nothing’s NORMAL) one definately gets a gold star right in the middle of his forhead.

After ten hours today now, I at least appreciate what I am trying to understand. May the ghost of Einstien fly up my nose.

This definately has a difficulty factor of 8 or I gotta buy the book.

Once again- I appreciate everyone’s help

AND… Has anyone been to http://www.photo.net– It would be way cool if this site also accomodated and displayed members motion graphics artwork– I know big task but I’m a dreamer.

Not only that but I feel that what is going on here is a forerunner to a widely accepted artform. I know it already is an artform but “the people” don’t even know it.

I’m a newbee but I think I should repost this message.