After Results has a project-wide bit depth setting, however particular person plugins could or could not assist all bit depths. And relating to rendering, numerous file codecs and codecs even have particular bit depth choices.
With regards to colour administration, bit depth is a technical setting that varies between totally different software program apps and recordsdata, and might change the best way that colours are saved and represented. Having a primary understanding of bit depth may help keep away from issues when engaged on initiatives and sharing recordsdata the place colour administration is essential.
Overlooking 16 bits, the center youngster
Within the context of video manufacturing and animation, all latest developments in colour administration have revolved round two issues: ACES, and High Dynamic Range. In After Results, working with HDR video requires initiatives to make use of the 32 bit float choice. In different phrases, 32 bit mode is linked to Excessive Dynamic Vary. The video above is for much longer than I believed it could be, however the intention is to attempt to hold the subjects of bit depth and HDR separate. Nevertheless the underlying assumption is that the rationale you’ll need to use 32 bit mode is so you should utilize HDR – and probably ACES/OCIO as nicely.
From a contemporary and pragmatic perspective, the subject of bit depth in After Results is targeted on utilizing 32 bit mode and never by accident compromising any excessive dynamic vary pixels.
Regardless of being a reasonably mundane matter, there’s a number of nuances concerned when discussing bit depth and After Results. When After Results was launched in 1993 it solely supported 8 bit colour. 16 bit colour was added 8 years later, after which 32 bit float mode a couple of years after that. There are a lot of potential mixtures of mission bit depth setting, plugin assist, and output file format / codec settings that may very well be examined, however the finish end result can be an amazing mess.
Subsequently, whereas the variations between 8 bit and 16 bit mode are demonstrated within the video above, it’s not the principle focus. What we’re actually concentrating on is the distinction between common “commonplace dynamic vary” video, and excessive dynamic vary. The variations between 8 and 16 bit modes are usually not practically as necessary as their variations to 32 bit float mode.
15+1 isn’t 16
…which is all main as much as a little bit of an embarrassing apology about 16 bit mode. As a result of we’re principally thinking about 32 bit mode, I don’t really feel so dangerous about posting a video that’s a bit mistaken. I’m kicking myself for making an novice mistake, however I’m consoling myself with the thought that I haven’t tousled the underlying idea.
The video introduces the idea of bit depth, and reveals find out how to calculate the variety of values you will have with a given variety of bits. With regards to 16 bits, then 2^16 is 65,536 – or a spread of 0 to 65,535. Within the video, I say that which means every pixel can have a price from 0 to 65,535 – or 256 occasions extra element than an 8 bit mission. For different graphics software program, this may be appropriate – and a 16 bit integer definitely does have a spread of 0 to 65,535.
However within the particular case of Adobe graphics software program – not simply After Results however Photoshop too – “16 bit” mode doesn’t imply what you suppose it would imply. For technical causes which were examined more deeply elsewhere on the internet, Adobe are literally utilizing “15+1” bits, giving a spread of 0 to 32,768. This nonetheless offers 128 occasions extra precision than a daily 0 – 255 bit pixel, and the underlying idea that extra bits = much less picture banding nonetheless stay.
Warning! Warning!
As a result of After Results wasn’t initially designed and written for HDR video, there are legacy elements and behaviours which don’t assist 32 bit float mode. That is the actual downside that customers want to pay attention to – one thing as harmless as utilizing the colour dodge mixing mode may end up in all HDR pixels being clipped. And whereas plugins have a warning icon in the event that they don’t assist the identical bit depth of the mission, even plugins that do assist 32 bit float mode could clip HDR values by default.
For those who handle to place collectively a 32 bit composition with excessive dynamic vary photographs, relating to rendering you continue to want to make sure that you render to a file format and codec that isn’t clipping any HDR pixels. Apparently, After Results will present a warning message in case your output file can have a fantastic bit depth than your mission – rendering a Prores 4444 from an 8 bit mission, for instance. In concept this shouldn’t be an issue, and the one consequence is that you simply may be losing disk area and creating bigger recordsdata than wanted. Nevertheless doing the alternative – rendering to a codec that has a decrease bit depth than the mission – does not produce a warning. However that is the state of affairs the place picture element and high quality could be compromised.
Clip go the shears
For those who’re working in a 32 bit mission, any plugins that don’t assist 32 bit mode will present a warning icon within the Results Controls panel. All plugins additionally present their bit depth compatibility within the “Results and Presets” panel.
Nevertheless, as famous within the video, there are nonetheless a couple of different behaviors that may clip excessive dynamic vary pixels in a 32 bit composition. The primary ones to be trying our for are:
Mixing modes: Colour Dodge, Traditional Colour Dodge, Vivid Gentle & Arduous Combine
Plugins: Take away colour matting, Noise
And the degrees impact can be utilized to intentionally clip black and white pixels to 0 and 1.
Name the Nanny!
One draw back to working with 32 bit float mode is the small potential for “NaN” pixels. A NaN pixel shouldn’t exist – NaN stands for “not a quantity” they usually’re typically the results of a bug within the rendering code. They solely appears to end result from working with floating level numbers. Hopefully you’ll by no means encounter one, nevertheless it’s value understanding that these evil bastards may cause all kinds of weird issues and behavior. The primary time you encounter a NaN you’ll suppose you’re going loopy!
Fortunately there’s a free resolution within the type of a plugin you may obtain from fnord software, called “NaNny”. For extra info, take a look at an older article I wrote about them so you may recognise the signs if one ought to pop up.
That is half 18 in a protracted sequence on colour administration. For those who’ve missed the opposite elements, you may 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 take a look at a few of my other ProVideo Coalition articles.
