• Adobe After Effects Expressions

  True Opacity

  Posted by John Madison on February 1, 2011 at 1:09 pm

  Hi guys,

  I have duplicated a layer in z space quite a few times and i’ve got a slider on another layer controlling its opacity (all the duplicated layers). The problem is the opacity doesnt seem to be real opacity. It seems one layer is affecting/influencing another layer and thus you get decreasing brightness rather than opacity. Is there any way to compensate for this?

  Dan Ebberts replied 15 years, 3 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  February 1, 2011 at 6:04 pm

  Can you post an example and/or better describe how you think it should look vs. how it actually looks? It’s hard to visualize how opacity could be anything other than “real” opacity.

  Dan
• 

  John Madison

  February 1, 2011 at 6:21 pm

  I’ve got a shape layer that is duplicated about 20 times in z-space. I’ve linked each of the layer’s opacity to a master slider to control overall opacity. If its done this way, you cannot see the bottom layer (suppose an image) until the opacity is very low, around 5%. I’m thinking its beacuse one layer’s opacity is affecting the other and hence you get a graying effect rather than a true opaque effect.
• 

  Dan Ebberts

  February 1, 2011 at 7:16 pm

  I think that’s just how opacity works. If I remeber correctly, the formula for stacked opacity is something like:

  100*(1 – (1-Opat1/100)*(1-Opat2/100)…)

  So if you have 20 stacked layers, each at 20% opacity, you’d expect the opacity of the stack to be about 99%, making layers at the bottom of the stack barely visible.

  If you reduce the opacity to 5% the opacity of a 20-layer stack would be about 36%. My math might be off a little, but I think thats the general idea.

  Dan

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