Linear compositing generally is a difficult topic. A few years in the past a number of of my colleagues began discussing it. One in every of them mentioned “I discover it straightforward to elucidate what linear compositing is, I discover it tough to elucidate to individuals why they need to use it.”
Now, engaged on this collection, I discover myself in the identical place. The fundamental idea of linear compositing is easy, virtually intuitive, however for the typical After Results consumer it represents a reasonably radical change.
After Results doesn’t do linear compositing by default, it’s a venture setting that must be manually enabled. Even when a consumer doesn’t allow After Results coloration administration (ie. the working house is ready to “none”) then all compositing operations are nonetheless gamma encoded. So the typical After Results consumer may have used gamma encoded compositing for so long as they’ve used After Results, except they’ve manually determined to not, by which case they’re not common!
Because the video factors out, linear compositing actually means “not gamma”, and so it helps to know gamma and gamma encoding first. This was the subject of part 7 on this collection, and in the event you haven’t seen it then I strongly suggest you head over and watch it first. It’ll assist every thing else make sense.
However linear compositing actually clicked for me once I found an article by Eric Brasseur. He first printed it in 2007, and once I learn it I truly saved a duplicate of your entire web site, as a result of I used to be fearful that such a precious useful resource would instantly disappear with no hint. I didn’t have to fret, as a result of it’s nonetheless on-line right this moment and appears precisely prefer it did 15 years in the past.
The article on Eric’s web site is generally to do with picture scaling, and it makes use of a specifically modified picture of the Dalai Lama to show how scaling is effected by gamma encoding. Sadly for me, the way in which the picture was modified additionally stopped it from being recorded as an MP4, and so my efforts to display file an indication have been thwarted. Nevertheless I’ve mocked up a fast nonetheless, however even this may not work on all gadgets appropriately, so I recommend you head over to Eric’s original article and try for yourself.
Whereas Eric’s article was the important thing to me understanding the problems of gamma encoded compositing, and the advantages of linear compositing, it was largely centered on picture scaling algorithms. However relating to visible FX compositing, linear compositing has a a lot higher impression than simply scaling. All picture processing operations, together with mixing modes, blurs, dissolves and extra, are all technically incorrect except calculated in a linear colorspace. And with the ACEScg colorspace and the EXR file format being linear by definition, understanding linear compositing is a basic side of coloration administration.
One factor I really feel a bit responsible about is utilizing the After Results “glow” impact for example within the video. It’s definitely true that the behaviour of many (if not all) plugins adjustments when linear compositing is enabled, and the glow impact is an efficient instance. Nevertheless within the case of the glow impact, I discover it really works a lot better, extra easily, and with far more sensible outcomes when linear compositing is on! And that is the case for thus many issues with linear compositing – when you get used to the change, then you definitely’ll realise that every thing seems and behaves extra realistically..
The video additionally refers to an article from Befores & Afters, you’ll be able to read the original here.
That is half 17 in a protracted collection on coloration administration. When you’ve missed the opposite elements, you’ll be able to catch up right here:
Part 4: Maxwell’s spinning discs
Part 6: Understanding the CIE 1931 chromaticity diagram
Part 8: Introducing Colorspaces
Part 9: The theory of a color managed workflow
Part 10: Using After Effects built-in color management
Part 11: Introducing OpenColor IO
Part 13: OpenColorIO and After Effects
Part 14: Combining OCIO with After Effects
Part 15: Logarithmic file formats
Unscripted: Looking at ACES and OCIO in After Effects 2023
AND – I’ve been writing After Results articles and tutorials for over 20 years. Please try a few of my other ProVideo Coalition articles.
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