- March 5, 2009 at 9:33 pm
Just a quick question. Is there any way to convert a movie to lab color space, apply an effect to luminance and chrominance, and then convert it back to its original color space profile?
Any input would be greatly appreciated.
- March 6, 2009 at 2:13 am
Often times, just duplicating your layer, and applying the desired effect, for example a Blur, then setting the transfer mode of the filtered top image to Luminosity (L) or Color (ab) has practically the same result.
For even more Lab-like manipulation (for example separate filters for a & b), try converting from RGB to Yuv, which is nearly the same as Lab, and the way in wich most digital video is encoded behind the scenes:
Create a comp with your video
give it 2 “Channel -> Channel Combiner” effects
set the first effect From: RGB to YUV
set the second effect From: Red to Red Only
Duplicate that layer twice and set the second effect in the new layers “green to green only” and “blue to blue only.”
Set the top 2 layers to transfer mode: screen, add or lighten (makes no difference)
Add an adjustment layer with Channel Combiner YUV to RGB. Everything should look back to normal now.
Now the bottom layer is Y (L), the 2nd to last = U(a) and the 3rd to last is V(b)
You can now apply any effect on any channel separately (place them after the channel combiners)
If you’d ever want to filter RGB separately, loose the Adj Layer, and the first RGB to YUV effects..
I hope that makes sense, just try it.
- March 6, 2009 at 11:39 am
Ah thank you Filip,
Thanks for getting back to me. I will give that a try as soon as I get a chance. Do you know of any resources for things like this such as color profiles etc? I have looked around online and havent had much luck apart from a few adobe white papers. It is all very interesting stuff.
Also to Dave sorry if my question was a little vague, I wasnt actually looking to apply it to any footage I am working on at the moment, but was just asking the question out of general wonder-ment.
Any more information would be awesome!
- March 6, 2009 at 3:33 pm
Well, the stuff I discussed doesn’t really have anything to do with Color space in the Colorsync sense of the word. It’s just about manipulating channels with effects as one would do in Photoshop by selected just 1 channel.
If you want some insight in Color management and using profiles within adobe apps (it’s confusing), I suggest you start at Stu Maschwitz’s Blog at prolost:
- August 27, 2020 at 4:28 am
Sorry to come back to this, it’s been so long. But please tell me what manipulations you need to do to repeat something similar from Photoshop when you copy information from channel “a” to channel “b” in Lab mode.
Here is an examples. https://imgur.com/a/143oxmg
I would greatly appreciate hearing answer from you.
- August 27, 2020 at 9:24 am
AFAIK there’s still no access to Lab colors in After Effects.
You can convert to YUV which is similar though technically very different to XYZ derived spaces such as Lab.
So the recipe would be:
Channel Combiner effect: RGB to YUV
Shift Channels or a Channel mixer: Take Blue from Green (or whatever), RGB are now YUV
Channel Combiner effect: YUV to RGB
If you do need it technically accurate, you could write a conversion function in MiLai PixelsCore.
That’s pretty hardcore though 🙂
- August 27, 2020 at 9:52 am
- August 27, 2020 at 10:04 am
The example with splitting it in separate layers was if you needed to add different effects on different channels (like a median on U, noise on Y, blur on V, then recombine)
Since you only want to copy a to b in Lab (U to V in YUV), in your case you can just add the three effects to 1 layer. Combine channels – shift channels – combine channels:
copy paste this on your layer
Adobe After Effects 8.0 Keyframe Data
Units Per Second 30
Source Width 1920
Source Height 1080
Source Pixel Aspect Ratio 1
Comp Pixel Aspect Ratio 1
Effects Channel Combiner #1 From #6
Effects Shift Channels #2 Take Blue From #5
Effects Channel Combiner #3 From #6
End of Keyframe Data
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