• Adobe After Effects

  order of operations question (blending smoke on to a background)

  Posted by Josh Reynolds on January 5, 2009 at 6:33 am

  I have a shot that I am adding smoke to.

  The smoke is practical footage shot against a black background.

  I have used the screen blend mode on the smoke footage to excellent effect. The smoke looks great but …
  It is white and I want it to be dark gray. I am at a loss of how to achieve this.

  The screen blend seems to be the last thing that happens in the order of operations so if I add a tint or whatever it mucks with the screen.

  Is this possible to do? It seems like it should be easy but maybe it’s because I don’t understand the math behind these operations.

  Does anyone have any suggestions on how I would do this?

  Thanks so much,

  Josh

  Josh Reynolds replied 17 years, 4 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Robert Paynter

  January 5, 2009 at 7:32 am

  Duplicate the smoke layer.
  Use the duplicate as a alpha matte.
  Make sure to turn the visibility for this layer off.
  Precompose the two layers and make the color corrections you wish.
• 

  Darby Edelen

  January 5, 2009 at 4:34 pm

  [Robert Paynter] “Use the duplicate as a alpha matte.”

  In this case you would want to use it as a luma matte.

  My suggestion would be the same as Robert’s (only you’ll need to use a luma track matte) and I would also recommend setting the pre-comp to the Luminescent Premultiply blend mode in your main comp. This will remove any black fringing and the smoke should come through nice and clear! Make any color adjustments to the pre-comp.

  Darby Edelen
• 

  Josh Reynolds

  January 6, 2009 at 3:29 am

  Brilliant!

  That did just the trick.

  You guys are awesome!

Reply to this Discussion! Login or Sign Up