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color difference keyer – HELP!
I hope you can help. I am having serious difficulty with the adobe after effects color keyer. I have looked high and low for a tutorial to no avail. I am following this tutorial diligently
https://library.creativecow.net/articles/onneweer_barend/keyingtut.php
However I can see I am being seriously let down by the color difference keyer. The adobe site offers no real answere ‘s to my questions.
There are 3 eye droppers in the preview of the effect. Which image do I use these on? The “Matte Uncorrected”?
The Black eye dropper goes onto the darkest part of the image (where it was green). What do the other two eye droppers get used for?What are they for?
If I use the white eye dropper on any whites it just turns anything that is black into white (i.e. the whole green screen)
I can use the eye dropper with a line through it on something white and I get somewhere but my mattes are RUBBISH!
Please can someone point me in the right dirrection?!
Thankyou
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3 Replies
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off course it is.
No, I find the help file NO USE at all. I can use the black dropper to drop on the lightest part of the A matte and then the darkest part of B matte. But using the white dropper really is getting me nowhere. I have more luck with the dropper with a line through it but that makes my edges far too hard. Matte in black and matte in white give me a nice bit of control. But I would love to know the correct useage of setting my white points with the white dropper and what the dropper with a line through its real purpose is?
http://www.thomasenglish.co.uk
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Yes Dave, you are a great help are’nt you. As I said in a previous post I have read the AE help and it is useless and unclear. Is it not bleeding obvious that the tutorial is about core mattes and edge mattes. Is there much point in you responding simply to condescend me if you have not used the function in years.
It talks about using the white dropper on the Matte without explaining which Mattes and it fails to clarify which “white” dropper.
To clarify, the white dropper referred to in the tutorial is the lined white dropper and the white dropper stuck in between the previews is simply a duplicate of the colour key white dropper.
The AE colour difference keyer seems to work by inverting our image in the colour channel chosen (matte A) where we set our Partial A in black by using the black dropper. We use this on the lightest point because we are looking for the brightest black to scale down.
The AE keyer seems to also take the red channel and make a luminence from that (matte B). Where we also choose the darkest post on the screen with our black eye dropper to scale up our chosen red luma matte.
You can scale each individual matte (a or b) by using the black and white matte outs. the matte B is basically a highlight matte so don’t expect the world from it.
The keyer then adds them together (screen blended) on the final matte. We can the scale our matte down to 0 or up to 1.0 using the matte in black or matte in white at the bottom. If you scale it too hard then you get uglier edges. If your doing a soft comp (edge comp) don’t scale it too much and if your doing a hard comp (core) scale it hard. Thats if your just using this keyer rather than hard comping with a chromo keyer a la tutorial.
So far this has taken me a while to work out. If anyone has any more tips I would be grateful.
Thankyou
http://www.thomasenglish.co.uk
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You are probably right with regards to reading for comprehension. After another night I am now getting fantastic keys but I still have not fully understood the B- Matte. I would also love to find a way to choke the AE color dif. keyer so I can hard comp and soft comp it better.
Anyhow, thanks for your help.
http://www.thomasenglish.co.uk
http://www.studio.pplmedia.com
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