HPA Tech Retreat — Color flow in the desert

By Jesse Korosi

I recently had the opportunity to attend the HPA Tech Retreat in Palm Desert, California, not far from Palm Springs. If you work in post but aren’t familiar with this event, I would highly recommend attending. Once a year, many of the top technologists working in television and feature films get together to share ideas, creativity and innovations in technology. It is a place where the most highly credited talent come to learn alongside those that are just beginning their career.

This year, a full day was dedicated to “workflow.” As the director of workflow at Sim, an end-to-end service provider for content creators working in film and TV, this was right up my alley. This year, I was honored to be a presenter on the topic of color flow.

Color flow is a term I like to use when describing how color values created on set translate into each department that needs access to them throughout post. In the past, this process had been very standardized, but over the last few years it has become much more complex.

I kicked off the presentation by showing everyone an example of an offline edit playing back through a projector. Each shot had a slight variance in luminance, had color shifts, extended to legal changes, etc. During offline editing, the editor should not be distracted by color shifts like these. It’s also not uncommon to have executives come into the room to see the cut. The last thing you want is the questioning of VFX shots because they are seeing these color anomalies. The shots coming back from the visual effects team will have the original dailies color baked into them and need to blend into the edit.

So why does this offline edit often look this way? The first thing to really hone in on is the number of options now available for color transforms. If you show people who aren’t involved in this process day to day a Log C image, compared to a graded image, they will tell you, “You applied a LUT, no big deal.” But it’s a misconception to think that if you give all of the departments that require access to this color the same LUT, they are going to see the same thing. Unfortunately, that’s not the case!

Traditionally, LUTs consisted of a few different formats, but now camera manufacturers and software developers have started creating their own color formats, each having their own bit depths, ranges and other attributes to further complicate matters. You can no longer simply use the blanket term LUT, because that is often not a clear definition of what is now being used.

What makes this tricky is that each of these formats is only compatible within certain software or hardware. For example, Panasonic has created its own color transform called VLTs. This color file cannot be put into a Red camera or an Arri. Only certain software can read it. Continue down the line through the plethora of other color transform options available and each can only be used by certain software/departments across the post process.

Aside from all of these competing formats, we also have an ease-of-use issue. A great example to highlight on this issue would be a DP coming to me and saying (something I hear often), “I would like to create a set of six LUTs. I will write on the camera report the names of the ones I monitored with on set, and then you can apply it within the dailies process.”

For about 50 percent of the jobs we do, we deliver DPX or EXR frames to the VFX facility, along with the appropriate color files they need. However, we give the other 50 percent the master media, and along with doing their own conversion to DPX, this vendor is now on the hook to find out which of those LUTs the DP used on set, go with which shots. This is a manual process for the majority of jobs using this workflow. For my presentation, I broke down why this is not a realistic request to put on vendors, which often leads to them simply not using the LUTs.

For my presentation, I broke down how to get around this LUT issue by staying within CDL compatibility. I also spoke about how to manage these files in post, while the onset crew uses equivalent LUTs. This led to the discussion of how you should be prepping your color flow at the top of each job, as well as a few case studies on real-world jobs. One of those jobs was a BLG workflow providing secondaries on set that could track through into VFX and to the final colorist, while also giving the final colorist the ability to re-time shots when we needed to do a reprint without the need to re-render new MXFs to be relinked in the Avid.

After a deep dive into competing formats, compatibility, ease of use, and a few case studies, the big take away I wanted to leave the audience with was this:
– Ensure a workflow call happens, ideally covering color flow with your on set DIT or DP, dailies vendor, VFX and DI representative
– Ensure a color flow pipeline test runs before day one of the shoot
– Allow enough time to react to issues
– When you aren’t sure how a certain department will get their color, ask!

Jesse Korosi is director of workflow at Sim.

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