linear workflow vs film emulation

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  06 June 2013
linear workflow vs film emulation

I've heard it so many times: Don't render with the photographic exposure node, you need to comp the shot in linear colour space. I understand this advice very well but I've always found a problem with it: The photographic exposure node is the only good film emulation LUT (until recentely, more about that later).

By film emulation LUT I don't mean just tone-mapping the gamma to 2.2 for display. I mean introducing a toe and shoulder to the exposure curve, effectively mapping a very wide exposure range to a narrower low dynamic range. It's no trivial matter as not many LUTs deal with high dynamic ranges, and curve tools are way too fiddly to do anything precise. It's also important artistically, as photographs are considered the most realistic depiction of reality.

To all the render and compositing artists: how did you tone-map your renders in comp to look anything like a real film exposure? Maybe film VFX folks are able to create high quality camera input LUTs and their reverse operation? Or did you just eyeball it?

Personally I use to stick with the photographic exposure, nailing the look in the beauty render as much as possible. I've recently come across a bootleg build of OpencolorIO for windows and After Effects. It includes various film emulations that work great, and also offers the reverse operations, such as converting a random sRGB image into linear space by unrolling it's highlights in a perfectly inversible way. That's the first time I come across a feature like this, and probably the first time that there is a true solution to colour management.

I'm interested to know more about this topic, please share your workflows around film emulation and colour management.

*edit: maybe this should go in the maya render sub-page?

Last edited by APerez : 06 June 2013 at 05:45 PM.
  06 June 2013
I'm pretty sure the reason people don't try to get the film look straight out of Maya is that you can achieve the same look afterwards with some post processing, and that gives you a lot more flexibility because if you do it straight in Maya you can't take it off. Rendering HDRI just gives you the ability to adjust exposure and whatnot afterwards to get it exactly where you want it, but you end up cutting it down to 8 bit in the end anyway.
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  06 June 2013
I understand this concept, and I'm wondering how people actually tonemap their image in comp, because I don't think it's as easy as applying a curve. The only decent tools I know of are OpencolorIO and GingerHDR but I've never seen them discussed around here.
  06 June 2013
Nuke and/or Lightroom are reasonably easy to apply a certain look.
My opinions are always my own...and maybe a friend's, but never my employer's.
  06 June 2013
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