I tried to apply an effect to a composition, but the effect had been applied to the whole composition and not to the contents of the composition. This composition consisted of animated shape layers, an adjustment layer and a rectangle background layer. When I removed this background layer, the effect had been applied to the composition contents.

What is the role of the alpha channel in applying the effects, and why hadn't the effect been applied until I removed this layer?

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(Click images to enlarge)

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  • I'm not sure I understand your question.. You apply an effect to a composition - and that effect is applied to the whole composition including its background - you remove the background and the effect is only applied to everything that is left.. What else do you expect to happen? And what does the alpha channel have to do with it? I may be missing something.
    – Cai
    Feb 21, 2016 at 16:33
  • I had applied a drop shadow effect to the composition when it includes the background layer and the shadow appears only to the whole composition not its contents , when I removed the background layer the shadow appeared to the composition contents not the whole composition , got it ? Feb 21, 2016 at 18:06
  • Ok, my point stands then, what else did you expect to happen? If you apply an effect to a composition then it applies to the whole composition, including any backgrounds or anything else. If you want to apply an effect to specific layers in your composition you need to apply the effect to those layers.
    – Cai
    Feb 21, 2016 at 18:37
  • I added screenshots to the question , please check it , in both situations I had added the effect to the composition directly . My question is why in the second situation when I added a background solid layer the shadow disappear from the contents and appear to the whole composition instead ? Feb 22, 2016 at 5:06
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    I'm not sure what else to say. If your composition has a background, the effect will be applied to that too, that is what should happen.
    – Cai
    Feb 22, 2016 at 7:20

1 Answer 1


In the bottom screenshot, the shadow was applied to the bounding box of the whole group. In the top screenshot, it is applied to individual objects. That is a typical behavior.

I think you were thinking that you could select all objects and apply a shadow and that shadow would be applied to each individual object, but instead it was applied to the entire selected group of objects. To avoid that, select an object individually and apply a shadow, then select the next object individually and apply a shadow, and so on.

  • What is the cause of this typical behavior ? Feb 22, 2016 at 14:55

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