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Green screen and colour correction. Which order?!


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#1 Phil Beastall

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Posted 30 January 2008 - 09:50 AM

I'm editing a film at the moment, and am going to be colourising the final video using Apple Color. We have some green footage which is going to be keyed but was wondering, in which order do you work. Do you key out the green, and merge with the background shot, and then colourise the scene as a whole? Or do I colourise then key?

I'm keying in After Effects. If I key out the green but do not composite with a background, and save that as a file, the background is saved as black. Is there a way to save the file so that rather than the background being stored as black, it keeps it transparent, so say I moved it into final cut pro, when I place it onto an image, it will work as it would in After Effects.

I'm just trying to work out the most effective order to edit these scenes.

Thanks
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#2 Thomas Worth

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Posted 30 January 2008 - 11:27 AM

You would both pull the key and do the final composite within After Effects. Final Cut Pro is an editor as far as I'm concerned, not compositing software. Yes, I know that technically FCP can do basic compositing, but you'll have more control over the final comp in software that is better suited for the task.

The color correction would be done in Color. Normally, color correction is never done until the show is completely finished with all visual effects added. It's the very last step prior to final output / downconvert / MPEG2 compression for DVD, etc. However, you will probably need to do some color tweaking to the image to get it to match the background plate. I would only make minor adjustments here to preserve your color tweaking options in Color.

To answer your question about the background being "black," you can export the keyed layer from AE as a QuickTime using the PNG compressor. This will keep the alpha channel intact so you can comp it over other stuff in FCP. Don't do it that way, though. Do it in AE. :)
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#3 John Brawley

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Posted 30 January 2008 - 05:57 PM

The color correction would be done in Color. Normally, color correction is never done until the show is completely finished with all visual effects added. It's the very last step prior to final output / downconvert / MPEG2 compression for DVD, etc. However, you will probably need to do some color tweaking to the image to get it to match the background plate. I would only make minor adjustments here to preserve your color tweaking options in Color.



Noone seems to do it anymore, but it used to work quite well to do two passes in telecine. The first pass you correct for the background surface that you're keying. Push the saturation and even it all out. You then use this layer to generate the matte. The second pass you do, you correct for the foreground elements. You might be trying to match the lighting in your foreground comp or tone to your final composite, so you can do what you need to there, and the correction is preserved, because you don't have to worry about the key that you generate. It's come from the first pass.

This only works if you plan to do it, and it sounds like it might be too late for you now.

and so, you should do the key and composite first. You can easily doa temp one in FCP just to check that it's going to work for the edit. Once you've locked of you edit, you can lay the clips off to AE. You then want to preserve your alpha channel so you can take the clips back into FCP for your final conform (which is a perfectly acceptable way of doing this).

You just need to use a compressor that support's alpha channels or millions+ (the + means alpha).

Some codecs add it as a fourth chanel, like RGB-A and some *premultiply* the alpha into the RGB signal.

Straight Alpha is the safest way to go. Have a look at the options when you're rendering out of AE. You also probably want to avoid any compression, in either HD or SD.

jb
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#4 Andres Pardo aka Gral Treegan

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Posted 02 February 2008 - 12:55 AM

I'm editing a film at the moment, and am going to be colourising the final video using Apple Color. We have some green footage which is going to be keyed but was wondering, in which order do you work. Do you key out the green, and merge with the background shot, and then colourise the scene as a whole? Or do I colourise then key?

I'm keying in After Effects. If I key out the green but do not composite with a background, and save that as a file, the background is saved as black. Is there a way to save the file so that rather than the background being stored as black, it keeps it transparent, so say I moved it into final cut pro, when I place it onto an image, it will work as it would in After Effects.

I'm just trying to work out the most effective order to edit these scenes.

Thanks


Hi!!

my personal advice as VFX supervisor is:

1- compose first then make the color correction.
2- if youre using after effects for key use keylight plugin or ultimatte plugin
3- keys in apple shake works better than in after effects
4- try color finesse in after effects for color correction, for me is better than apple color

Best Wishes
Gral. Treegan
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#5 Phil Beastall

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Posted 04 February 2008 - 04:36 AM

Thanks for the advice. Defo makes sense to do the chromakey work first, and match the two shots, and then colour treat the composition as if it was actually shot without green screen.
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#6 Hugh Macdonald

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Posted 18 March 2008 - 06:56 PM

My preference on this one would be to neutralize/match all of the similar clips before the composite. This way the comper has an easier (and therefore more efficient) job comping the multiple shots. The neutral grade should be as "normal" as possible, with as much colour information retained. Then any specific grade should be applied after the composite (although it's always useful for the comper to be able to see what their shot is going to look like after the final grade....)
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#7 tylerhawes

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Posted 19 March 2008 - 01:18 AM

Not that it helps you given your toolset, but the way this should be done is to have a color grading system that allows you to import an alpha matte for the shot. This way you can color-correct the foreground and background separately in your DI system. This is a relatively new feature. I know Baselight, Nucoda, Quantel have it. I think Lustre has it now. It's been a feature request of mine for FinalTouch since 1.x (now Color), and I know they've done some work on it but it has never made it into a release version.

So yes, grade it all best you can in AE and then just do an overall adjustment in Color for final...
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#8 Markus Manninen

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Posted 03 April 2008 - 10:58 PM

Not that it helps you given your toolset, but the way this should be done is to have a color grading system that allows you to import an alpha matte for the shot. This way you can color-correct the foreground and background separately in your DI system. This is a relatively new feature. I know Baselight, Nucoda, Quantel have it. I think Lustre has it now. It's been a feature request of mine for FinalTouch since 1.x (now Color), and I know they've done some work on it but it has never made it into a release version.

So yes, grade it all best you can in AE and then just do an overall adjustment in Color for final...


Yes Lustre has a TGA file (RGA channels) where each channel works as a matte for your color correction. It's awesome. I wish it was unlimited mattes thou. One can dream.
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