Alpha Channel

[Portal]

Hey Guys,
I have been doing a lot of stuff that is requiring me to fly elements over moving back grounds and have been having issues with the transparent black making things that arent black too transparent. Can someone give me a quick run thru on exactly what the power of the alpha channel is and what can truly be done with it when using a catalyst ? This is on version 3.3

Thanks a lot

Cameron Yeary
UVLD

[samsc]

you want to do it properly?
so that it looks 'professional'?

where did your source footage come from?
what codec does it use?
r

[Portal]

you want to do it properly?
so that it looks 'professional'?

where did your source footage come from?
what codec does it use?
r


I would love to be able to have a moving background ( i.e any stock catalyst loop or anything else i have made. i usually use photo jpeg ) and then fly a jpg over the top of it except make the " black " back ground disapear. The problem is that anything that is not the opposite of black ( i.e . White ) seems to become partially transparent as well. I do want it to look like somethign i would see in a well edited video.
I use this a lot in corporate situation where I want to be able to put there graphic or logo over my back grounds.

Hope this helps. Any Ideas ?

Cameron

[tharding]

Use PNG files. Essentially they are the 16bit equivalent of GIF which supports transparency. Just make sure you have a transparent background in Photoshop and save as PNG.

No need to use transparent blacks. Catalyst will see the transparency automatically.

Cheers

Toby

[samsc]

yes.

if you have a static foreground with moving background

use png or tiff files created in photoshop.

use layers to create transparency.

---

if you want a moving foreground thats a whole different can of worms.
you need to have some real experience doing this in post-production - before beginning to do this type of thing.
keying ( green screen or whatever ) - is not as simple as it first appears - particularily with digital video sources.

[Spam Butterfly]

Native photoshop format (.psd) also supports alpha channels.

Hugh

[samsc]

Native photoshop format (.psd) also supports alpha channels.

Hugh

you cant use native photoshop files - the alpha channel is pre-multiplied - or the wrong way round for me.
also layered photoshop files include a hidden composite layer - that overrides any alpha information when imported into catalyst.

----

you need to use png and tiff.
this was explained in some detail many moons ago.
search for png in catvx

[Portal]

Thanks Guys this is perfect.

Cameron