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TUTORIAL: Ghost trails

Posted: Mon, 6th Sep 2004, 3:34pm

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Simon K Jones

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Chromanator Tutorials: Chromanator Misc - by Arktic

Ghost trails

The 'ghost trail' effect is usually used to emphasise speed, or to create a creepy or eerie appearance to a character. Using Chromanator, you can replicate this effect with very little hassle.

First of all, you need to isolate your actor/subject, either through extensive use of a garbage matte or by filming your actors against a blue or greenscreen. The blue/greenscreen option is much easier and faster. This is the clip that I'm going to be keying :

I'll use a colour difference key to remove the bluescreen, and then add in a suitable background:

I now need to make a copy of the footage of the actors. I right click on the clip, select “Copy”, and then right click on the layer below, selecting “Paste”. Now I have two of the same clip:

This second clip needs shifting a few frames to the right, so that the trail will be visible. Here I've cropped the end of the shot just to keep everything neat :

This means I have two copies of the actors over of the background :

I have to make this clip look a little more like a ghost trail and less like a clone of the actors, so to do this, set the composite mode to ‘add' under the clip's properties:

Now I need to grade this clip to enhance the ghostly appearance. I can do this by altering the Transparency and Box Blur RGBA of the clip under “Effects” in the object view:

You can alter these to whatever you like, depending upon the style you want your ghost trail to be.

I've set mine to a very low blur (about 2 or 3 percent), and high transparency, which gives me something like this:

I want my trail to fade over time, rather than being constant - so I also need to keyframe the transparency so that the trail fades. This is simply done by having a key frame at the start of the clip set to around 90% transparency, and one at the end set to 100%.

If you wanted a trail that was constant and did not fade away, then leave out the above step.

The effect is starting to look good - but not really like a trail as such. To get that ‘trailing' effect, I need to make multiple copies of the clip I've just been working on, and place them on the timeline, only shifted a little to the right each time:

And you should end up with something like this -

Last edited Wed, 2nd Mar 2005, 5:44pm; edited 1 times in total.

Posted: Mon, 6th Sep 2004, 4:15pm

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Simon K Jones

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Thanks and congrats to Arktic for writing the first guest tute. smile
Posted: Mon, 6th Sep 2004, 4:50pm

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Evman

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sweet. Arktic, post something here so I can plus 1 you.
Posted: Mon, 6th Sep 2004, 4:58pm

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Arktic

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Hey smile

Thanks goes to Tarn for helping me get this tutorial posted.

Hope it's usefull to you guys!

Cheers,
Arktic.
Posted: Mon, 6th Sep 2004, 10:19pm

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Gibs

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Nice tut. I guess I can take credit for originally inspiring the idea, but you did a good job of explaining it, Arktic. smile
Posted: Tue, 7th Sep 2004, 5:05pm

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Klut

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I wish I had a green screen so I could have tried this one...

But I don't sad
Posted: Tue, 7th Sep 2004, 5:30pm

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Simon K Jones

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Isolate the subject using garbage mattes instead. It'll take longer, but it'll work just the same.
Posted: Fri, 29th Oct 2004, 8:24am

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haklia

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Hi,

well, in fact I do not understand the difference between the 2 composite modes. Can someone explain it to me ??

Thanks
Posted: Fri, 29th Oct 2004, 9:29am

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Cogz

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There are two composite modes in Chromanator, Normal and Add.

Normal composite just simply overlays one frame/object onto another, and when rendered the only the pixels in the object on the top are seen. Example, put your hand onto the desk, you can't see through your hand to the desk can you, thats Normal composite.

Add composite will blend the two (or more) objects together, "adding" the pixel values, so again if you put your hand on the desk, you would see the colours of your hand AND the desk blended together.

Hope this makes it a little clearer, I can do some example illustrations if you still don't understand.
Posted: Fri, 29th Oct 2004, 9:36am

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haklia

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Oh yes, really thanks.

Chromy is great.
Posted: Thu, 25th Nov 2004, 2:15am

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Mr_E_Man

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woah...how'd you get the blue to key out so well without spilling onto the black? I've had problems getting black to work on my bluescreen.
Posted: Sun, 28th Nov 2004, 4:44am

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Arktic

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Hey Mr_E_Man,

It's just a case of playing around with the black and white points. I tend to leave a slight 'fringe' of blue round the actors, and then use the spill suppression to get rid of that.

I hope this helps,
Arktic,