Is there a tutorial about using alpha channel effects with all its glory?

Thank you

I am mainly interested in secondary color correction.

As far as I know, no such tuorial exists (yet).

Which application is similar to KDEnliove from the filter and usage concept so that i can learn there how to use the alpha filters?

Sony Vegas?
final cut pro?

??

I am willing to make such tutorial videos once i get an understanding.

Not sure how colour correction is anything to do with alpha channel.

But ...

I wrote up what I taught myself about alpha channels gorey details with respect to the alpha shapes effect at
http://userbase.kde.org/Kdenlive/Manual/Effects/Alpha_manipulation/Alpha...

That experience taught me a lot about alpha channel effects. Might be worth a read.

I also curated together 4 tutorials on blue screen at
http://userbase.kde.org/Kdenlive/Manual/Effects/Alpha_manipulation/Blue_...

If you want to change only the color of a T-Shirt of a person, you need to select the t-Shirt only to be able to collorcorrect it.

One way is to do a color selection to do an alpha channel color selection and then correct only the content seleted by the alpha channel.

I dont see any other way in KDEnlive to do secondary color correction.

I have found out that in FinalCut Pro secondary color correction is much easier to handle.

Hm, you description is explaining only Composite.

How about Alphain Alphaout Alphaover alphaxor alphaatop ???

Thank you

Selective color adjustments don't need an alpha channel it can just be via a matrix. In terms of using an alpha channel for color correction I think searching mattes and masks will provide some ideas. Your T shirt example, if selective color adjustment is not an option then roto'ing the area or pulling a chromakey matte as a mask and overlay then affect color through the matte.

What would be useful is an adjustment layer like AE and Photoshop and ability to use a mask without another overlay.

Perhaps this is possible already in kdenlive, rarely use color correction in kdenlive as its 8bit. Hopefully MLT GLSL will land soon and speed it up and improve precision and jbm's tracking feature will enable track mattes to be used.

"How about Alphain Alphaout Alphaover alphaxor alphaatop ???"

Dunno anything about them.

Maybe you can write them up when you figure them out. :-)

Some data on these transitions at http://www.mltframework.org/bin/view/MLT/PluginsTransitions

For an explanation of alpha compositing modes see here:

http://en.wikipedia.org/wiki/Alpha_compositing

but I think Composite is the mode to use for color correction.

RGB adjustment has an "alpha controlled" option, enabling some secondary correction to be done without compositing.

http://www.youtube.com/watch?v=Sj0sSkwu_fA

Can that be that noone ever used this damm filters and was able to make it usefull?

I generate some effects, but i just dont get a clue how this things work together.

The guy in the video got it a bit wrong: the "selection on checkers" mode is only intended as a kind of setup and debugging tool, to see where your alpha is transparent and check what the alpha operations are doing, etc.

To see the composite, it should be off - the selected display mode in the alpha operations plugin should be "image".

Also, in Kdenlive the alpha transparency is not automatic, you must add a "composite" transition.

You will not see any thing for alpha effects until you have
1. an alpha channel defined on a clip,
2. Overlapping clips
3. Some sort of transition between them

So you would only expect to see stuff at 60% in you YouTube clip where you have the green,red and alpha in transition.

From my reading of the frieOr doco alphain, alphaover etc transitions are providing the different alpha composting modes - the ones documented in Mario's wiki link. Many of these operations are provided in the composite transition. And are also available from the alpha shapes effect which I think you are using.

If you have a look at the user base article on alpha shapes I mention how the alpha operations modes are only really relevant when you combine multiple alpha channels. The operations define how alpha info from two different tracks are to be combined.

And I am guessing that this also the case with the alphain' alpha or etc transitions.
So you might start to see some effect of the alpha in if you have three tracks - two with alpha shapes on them.

I suspect not too many people use the alphain' alpha or etc because composite does the same things.

But the other thing to note is that preview of alpha effect is for me sometimes dodgy due to what looks like a bug. See the user base article on alpha effects. You might find the result of the alpha compositing different to the preview when you render it.

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