VFX workflows

[Eugene Lehnert]

When giving plates to VFX houses what colorspace are you using these days? I've always given 16-bit Log files. Has anyone tried using open EXR? Is it better to work using a linear workflow these days?

How are you mixing your VFX and native .R3D data on a timeline? If I give a VFX house Log files is it best to set the entire project to Log and grade through a LUT to color grade in Rec709?

 

[Marc Wielage]

How are you mixing your VFX and native .R3D data on a timeline? If I give a VFX house Log files is it best to set the entire project to Log and grade through a LUT to color grade in Rec709?

Generally if you're mixing a lot of VFX and regular shots, I would make them all the same format like DPX or ProRes 444 just to even the playing field. The key is to make sure the debayered files have sufficient range for grading. The FX people can apply a Rec709 LUT or a custom LUT so they can see their work in the correct color space, yet still give the post crew range to adjust the plates in the final. Rec709 is pretty standard in my experience, using calibrated monitors. There are good points to be made for using 16-bit linear EXR files, but I haven't yet used them in any projects.

Jeff Okun and Susan Zwerman's VES Handbook of Visual Effects: Industry Standard VFX Practices and Procedures goes into a lot of this stuff in great detail. In truth, there's a lot of ways to deal with the process, but they key is to do workflow tests to make sure everybody is on the same page and there are no last-minute surprises when the final VFX are coming in at the end of the project.

BTW, if you've got a very VFX-centric project, you'd be very wise to add a VFX editor and VFX supervisor to your project who understands various workflows and knows all the traps and potential problems, along with ways to avoid them.

 

[Gavin Greenwalt]

DPX and EXR are effectively equal. You can use linear or you can use RLF. All that is going to happen is if you give them RLF they'll apply a Log2Lin operation and make it into linear. If you give them linear they'll just use it as linear. So long as they understand a proper linear light workflow they should have no problem going from one to another. It's harder to go from Redgamma to linear so I would avoid that. Also don't apply any unpredictable color corrections to the footage like curves or saturation, that's the stuff that's non-trivial to match. If you are really kind you can send them EXR/RLF DPX and also send along a rough graded-LUT for them to use in their viewers.

Marc hit the nail on the head though. It's all about making sure they have all the data. If you keep it at RLF or EXR you'll be fine. But if you get fancy in the metadata with curves or contrast on top of RLF for example you can clip data and de-linearize the image which makes it tougher to match CG elements. And if you clip or crush data then they'll have no choice but to try and match your clipped white points and crushed black points and when the colorist tries to bring them back they'll just be gone. The less you do, the more likely the footage is to be error free. It used to be that RED footage out of the gate was clipped and faulty, but these days the opposite is generally true. I generally reset all of the metadata to RLF with a 5600k or 3200k white point and nothing else from default then export as a 10bit RLF DPX at 400-800 ISO. In my experience that generally melds well with what colorists ask for too. When I've completed a VFX plate I then simply return the plate exactly how I received it. I put it back into log DPX if I received log DPX or I return it as EXR if I received EXR. My philosophy is that from a post production standpoint nothing was done to the plate--it just magically now has VFX applied in a different folder. That way the colorist can start on the same plates I started with and when I'm done, just swap the original image sequence for the VFX tweaked image sequence.