In this tutorial, we'd like to show you how simple it is to use a GlamourKey file with a straight alpha channel. The alpha channel is information in a pixel specifying how that pixel should be merged when it's placed over another pixel.
There are two ways to store the information about a pixel's transparency, one is called a straight alpha channel; the other is called a pre-multiplied alpha channel. Let's dig deeper...
MATH IS THE KEY
Not to bore you with math, but it's critical to understand the difference between a pre-multiplied alpha channel and a straight alpha channel. Here's the easy way to remember it: in the pre-multiplied alpha channel, pixel over pixel information is exported out - but percentages about transparency have been changed. Basically, they've been either rounded up or down. Hence the term: "pre-multiplied."
By using straight alpha, all of the information is kept with the file. The straight alpha channel provides more precise information for your editing or compositing software. When our content is placed in Final Cut Pro, Avid, Adobe Premiere, Motion, Shake, After Effects, etc. - straight alpha gives you accurate color information around the edges / transparency of the subject. This results in an extremely high quality key - especially around the edges, where transparency is everything. You'll notice this in the hair of our models, where we strive to protect every strand. It results in a more believable finished product and a beautiful composite.
Better compositing, better quality with drag and drop ease.
KEYING IN ON THE PAYOFF...
Enough math, let's have some fun!
After you download one of our files and play it back in QuickTime, you'll notice roughness around the edges (this depends on your version of QuickTime).
Here's another example - note the fuzz around our model's hair and waist:
This is what a clip with a straight alpha channel looks like before you put it in an editor or compositor. What you're looking at are super smart pixels packed with information about transparency. The pixels are ready to share their knowledge with your editing or compositing program. Let's first go to Final Cut Pro to see what happens when we import the file into the browser and drag and drop it onto the sequence (It's placed on top of a gray background):
Final Cut takes into consideration all the information from each pixel - perfect!
Here's another example, this time in After Effects (again over a gray background):
From this point, you can adjust the file as you see fit, adjust colors and blend it into your background. Tweak it to your heart's content! (In the image below we added a little yellow and green to make our model blend into the field):
We want you to have an easy time using our content - so you can put more time into creativity. You'll find a ton of flexibility in our GlamourKey pre-keyed files.
We hope you enjoy using our content!
