“Correct” way to use blending when working linear?

[Kevin Camp]

removing white or black backgrounds is quite easy in Ae without using blending modes. it’s so easy i wish i could do it in photoshop too.

to remove black, add the channel combiner effect and set the ‘from’ property to ‘max rgb’ and the ‘to’ property to ‘alpha’. then add the remove color matting effect with the background set to black (default setting).

to remove white, do the same, but in the channel combiner effect, click the ‘invert’ option and then set the remove color matting color to white.

you can also save each of the setting off as animation presents to quickly recall as needed.

Kevin Camp
Art Director
KCPQ, KZJO & KRCW

[Walter Soyka]

If black is clamped to 0, Add will “remove” it. If White is clamped to 1, Multiply will “remove” it. In both cases, though, the remaining pixels will mix with the image accordingly, and that may not be what you intend.

If you want to eliminate black (or white) from footage and use Normal blending to composite it, you can look to Channel Combiner as Kevin suggests, but note that Channel Combiner is an 8bpc effect. I’d suggest instead using an UnMult effect; there are several free or low-cost options:

https://mekajiki.onfastspring.com/unmult
https://www.redgiant.com/downloads/legacy-versions/
https://www.redgiant.com/user-guide/universe/unmult/

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive   |   RenderBreak [blog]   |   Profile [LinkedIn]

[Daniel Waldron]

I usually use the free UnMult effect that Walter mentioned or the Extract effect. Extract will work with white as well.

[Walter Soyka]

[Daniel Waldron] “I usually use the free UnMult effect that Walter mentioned or the Extract effect. Extract will work with white as well.”

To use UnMult to knock out a white background, make an UnMult sandwich. Use an Invert effect, then UnMult, then Invert again.

You can also use a Levels or Curves effect on the RGB channels before the UnMult to affect what will be removed, or a Levels or Curves effect on the alpha channel afterwards to modify the new transparency directly. Just watch the edges!

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive   |   RenderBreak [blog]   |   Profile [LinkedIn]

[Maria Smith]

But what if I want to composite a .mov-file containing fire against a black background? Is it a bad idea to work linearly and use “Add” to get rid of the black background? I prefer not to use third-party plug-ins, and when I use the “Extract”-effect I always end up with an something unrealistic (like a sharp edge around my object).

[Walter Soyka]

Add is a good way to capture the light from fire, but note that if there’s also smoke, Add will not blend the smoke correctly.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive   |   RenderBreak [blog]   |   Profile [LinkedIn]