How to make 'alpha elements'

[terrypin]

Following generous help from guns1inger in a recent thread I was able to successfully download a lot of free 'elements' for possible use as effects in my family DVDs. But they are effectively 'normal' clips, albeit of a very impressive variety. None of them appear to belong to the special category which I gather are called 'alpha elements'. These seem to come as pairs, an alpha part and a 'normal' part, and are used for transitions, overlays and 'lower thirds' (whatever they are!).

However. they seem quite expensive from the sources I've seen. So I'm hoping someone can briefly explain the principle behind these please, so that maybe I can have a crack at making some myself.

Of course, if anyone knows a source of any free ones, that would be good too please.

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Terry, East Grinstead, UK

[guns1inger]

'Alpha Elements' or Alpha Channels are essentially masks that allow for transparency or overlay effects. Depending on the format, they may be separate files, or they may be a part of the the file with the graphics. Example - jpeg image files do not have Alpha channels, TGA files may have alpha channels. They can also be video elements to create moving masks.

Alpha channels/elements/masks are gray scale, with black being 100% transparent, white being 100% solid, and the grays being whatever is in between.

You can create them in pretty much any video or graphics editor. How complex they are depends on what you need to achieve with them, and what tools you have available. Photoshop, PaintShop Pro (Now a Corel product under a new name) or Paint.net can all be used to create still image masks. For moving masks it can be harder.

The other thing to look at is whether or not you can use the masking tools built into your video editor to create masks on the fly where alphas don't exist. This is often faster and simpler than created dedicated masks.

Have a browse around Detonation Films (http://www.detonationfilms.com/free_stuff.htm). It is an ugly site to move around, so don't rush. Here you will find all sorts of bangs and sparks etc for effects works. There are plenty of freebies scattered around the site, including clips with black backgrounds, for luminescence masking, clips with chroma-key backgrounds, and even clips with alpha masks. There is also a tutorials page with a pile of video tuts on compositing in various packages.

Should be enough to get you started.

[edDV]

Graphic "objects" with alpha are created in programs like Adobe Illustrator. You can create objects from photos in programs like Photoshop using various tools to separate the desired area from the background and then assigning an alpha layer.

Live action (people and things) can be shot against a green screen using a process known as chroma key. The result is video track with a companion alpha track.

Alpha is used for both edge definition and pixel by pixel transparency definition within an object.

Objects are layered over a background scene using a process known as compositing.

[terrypin]

Excellent, thanks both. That more than gets me started. Making my first (static) one now, as a TGA in PaintShop Pro. MEP 14 does indeed have some powerful relevant tools itself, guns1inger, so that looks like being the most productive approach as you suggested.

Heck of a lot to learn though!

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Terry, East Grinstead, UK