possible to apply a gradient to opacity? at DVinfo.net

David J. Payne · July 3rd, 2007, 05:37 AM

Hi I have a video of some smoke that I would like to appear to get thinner as it moves towards the sky. Is it possible to set the opacity level at the bottom of the clip to say 50% and have it diminish to 0% the nearer it gets to the top of the video?

Any help would be greatly appreciated!

David

Conor Ryan · July 3rd, 2007, 10:53 AM

In AE you can apply a black to white ramp to one layer and then use that as a matte layer for your smoke.

David J. Payne · July 5th, 2007, 03:50 AM

Connor,

many thanks for your prompt reply. I havent had a lot of experience in mattes but I will certainly give this a go, it seems to make sense. Would be even better if I could link numerous smoke clips to the same full screen matte.

Thanks again
David

Conor Ryan · July 5th, 2007, 05:37 AM

Yep, that can be done. You can make any layer a matte for another, and one layer can matte as many layers as you want. You can also precompose all the smoke into one layer and matte just that one.

Cole McDonald · July 5th, 2007, 09:39 PM

Most editors will allow you to apply a gradient as a "luma mask". This will do what you're looking for without having to go to an outside program.

Giroud Francois · July 6th, 2007, 01:11 AM

i do not see the reason of doing it after the shoot.
the filter will just make all the picture darker, including the smoke, so it will not increase contrast between smoke and background, just make it darker.
you should have put a real filter while shooting (and even there, the effect is almost the same).
the correct solution would be to put a light on the smoke.

Cole McDonald · July 6th, 2007, 04:43 PM

What editor, specifically, do you use for editing video? Final cut, vegas, premiere...other ;) We could get you specific directions for how to make a luma mask for this effect.

Nathan Quattrini · July 10th, 2007, 09:32 AM

Quote:

Originally Posted by Conor Ryan

one layer can matte as many layers as you want.

I haven`t found a way to do that in AE 7....care to enlighten?

Conor Ryan · July 10th, 2007, 10:33 AM

Quote:

Originally Posted by Nathan Quattrini

I haven`t found a way to do that in AE 7....care to enlighten?

Of course...I phrased it a little bit incorrectly though (damn memory)...

First way, really clunky - say you have three layers. Your top layer, 1, is the matte layer, your black and white ramp. layer 2 and 3 will be matted. set layer 2 to a luma track matte (the matte being layer 1). Layer 3's matte must be layer 2, the alpha channel of which has been affected by matte 1, so set the next matte (for 3) to an alpha inverted matte. Repeat. It can get really tricky to manage, as you have to flip between alpha and alpha inverted as you go down, so it's better to use the...

Second way, much better - put all your layers into the comp. Put the ramp on top and set the blending mode of that layer to stencil or silhouette luma. Do other stuff in this comp, or nest this as a layer in the next comp. This is much better because it's easier to go back and adjust.

Third way, meh, why not? - Place all your layers in a precomp, bring that into the next comp then do the above, or mask.

July 3rd, 2007, 05:37 AM	#1
David J. Payne Major Player Join Date: Oct 2005 Location: Southend-On-Sea, England Posts: 368	possible to apply a gradient to opacity? Hi I have a video of some smoke that I would like to appear to get thinner as it moves towards the sky. Is it possible to set the opacity level at the bottom of the clip to say 50% and have it diminish to 0% the nearer it gets to the top of the video? Any help would be greatly appreciated! David

July 5th, 2007, 09:39 PM	#5
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,675	Most editors will allow you to apply a gradient as a "luma mask". This will do what you're looking for without having to go to an outside program. __________________ Web Youtube Facebook

July 6th, 2007, 04:43 PM	#7
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,675	What editor, specifically, do you use for editing video? Final cut, vegas, premiere...other ;) We could get you specific directions for how to make a luma mask for this effect. __________________ Web Youtube Facebook

July 3rd, 2007, 10:53 AM	#2
Conor Ryan Regular Crew Join Date: Oct 2004 Location: Dublin, Ireland Posts: 67	In AE you can apply a black to white ramp to one layer and then use that as a matte layer for your smoke.

July 5th, 2007, 03:50 AM	#3
David J. Payne Major Player Join Date: Oct 2005 Location: Southend-On-Sea, England Posts: 368	Connor, many thanks for your prompt reply. I havent had a lot of experience in mattes but I will certainly give this a go, it seems to make sense. Would be even better if I could link numerous smoke clips to the same full screen matte. Thanks again David

July 5th, 2007, 05:37 AM	#4
Conor Ryan Regular Crew Join Date: Oct 2004 Location: Dublin, Ireland Posts: 67	Yep, that can be done. You can make any layer a matte for another, and one layer can matte as many layers as you want. You can also precompose all the smoke into one layer and matte just that one.

July 6th, 2007, 01:11 AM	#6
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	i do not see the reason of doing it after the shoot. the filter will just make all the picture darker, including the smoke, so it will not increase contrast between smoke and background, just make it darker. you should have put a real filter while shooting (and even there, the effect is almost the same). the correct solution would be to put a light on the smoke.