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Substituting colors

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Oliver de MorasséSubstituting colors
by on Jul 25, 2014 at 2:02:20 pm
Last Edited By Oliver de Morassé on Jul 25, 2014 at 2:14:31 pm

We have material of a model shot in front of a greenscreen and have used several keying effects (color key & keylight) to remove the green and leave a transparent background. Unfortunately, the dress the model is wearing has a slight tinge of green within - after keying, the dress is now silver/grey. Is it possible to substitute the grey for another color & put back to slight tinge of green? What's the best way of doing this?

Thanks for your help/tips

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Michael SzalapskiRe: Substituting colors
by on Jul 25, 2014 at 2:39:59 pm

Don't use spill suppression. This may leave some edges on her skin that look green, so you will need to do spill suppression on her skin and not on the dress. This means you'll need to do some garbage masks at the very least. Possibly some full-on rotoscoping.

Alternatively, do some better pre-production planning and reshoot on a blue screen or with a different wardrobe.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

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Dave LaRondeRe: Substituting colors
by on Jul 25, 2014 at 5:02:15 pm

I agree with Michael -- reshooting is probably the wisest choice if at all possible. Keying green on green is iffy at best.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA

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Conrad OlsonRe: Substituting colors
by on Jul 25, 2014 at 5:40:00 pm

It is usually easier to treat the key and the colour correction as two different steps. Precomp the layer with the key and place that over a copy of the original plate, and set the track matte mode of of the plate to alpha. That way you have the original image held out by the resulting alpha of your keys.

Once you have this setup is it much easier to apply colour corrections to your plate without effecting the results of they key, and without the spill suppression applied by Keylight.

There is a spill suppression node in After Effects that you could apply and that might give you more control, or you can use any other colour effects. You might have to do some garbage mattes but you should be fine.

Too many times people give the answer 'reshoot it'. In some cases this is useful but dealing with spill suppression, and having green objects on green screen, is relatively common, even on Hollywood movies that I work on. You can't always reshoot, sometimes you just have to make the stuff you have work.


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Oliver de MorasséRe: Substituting colors
by on Jul 28, 2014 at 3:04:17 pm

Thanks for all your feeback.

We had pre-informed the talent that green was a no go - she didn't think that the green tinge would interfer with the post! Unfortunately, in this particular case a reshoot is also not possible.

Thanks Conrad for your suggestion. Using your "track matte mode" method, I was able to get back the green tinge. I had to work a little more on the key around areas such as hair... but on the whole we are happy with the result - many thanks!

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