The Lost Bus is a 2025 survival-drama directed by Paul Greengrass for Blumhouse Productions in association with Comet Pictures and Apple Original Films. The film is based on the non-fiction book Paradise: One Town’s Struggle to Survive an American Wildfire by journalist Lizzie Johnson. Set against the 2018 Camp Fire in Paradise, California, it follows a school-bus driver and a teacher who fight to guide 22 children to safety through an encroaching inferno. Combining Greengrass’s documentary-style direction with large-scale visual effects and environmental reconstruction by RISE FX, the film depicts one of the deadliest wildfires in recent history with stark realism.

Supervising the inferno: Oliver Schulz (IMDB | Linkedin) is a senior Visual Effects Supervisor at RISE FX, the Berlin-based VFX studio. Over more than a decade at RISE he has guided VFX supervision on major international productions including Fantastic Beasts: The Secrets of Dumbledore, Blue Beetle and Megalopolis, among many others.

His background spans concept art, digital matte painting and 3D environments; skills that helped him to take the creative lead on blockbuster-scale environment and FX heavy shows. In this interview he reveals how he and his team at RISE tackled the challenge of recreating a burning landscape for The Lost Bus, combining procedural geography, wind-driven vegetation, deep-rendered volumetrics, and machine-learning techniques for depth integration, to bring the inferno to life on screen.

DP: How did you get onto the Lost Bus? 

Oliver Schulz: I came on board after wrapping up on Megalopolis and jumped onto the very first meeting with Charlie Noble and Gavin Round, Production VFX Supervisor and Producer. The project was already awarded at that time so we directly started talking about the Sequences and the scope of the Rise portion of work.

Luckily or better sad tragically this was a real event so in regards of look, there were many references and documentation of this day. So our first meeting was looking through a lot of real world footage from all available sources. Charlie had been prepping reference reels from the very beginning, so we could hone in on a lot of specific ones for each portion of the work because he had references for all of them!

DP: Roughly how big was the RISE team on The Lost Bus, and how long did you spend from first build to final comp?

Oliver Schulz: We started with a very small core team in May 24 and delivered the last shots at the beginning of 25.  I think around 50-60 people worked on the show in total during the production with up- and downramping based on specific project needs like temp deliveries for example.

DP: The antagonist of the movie is the geography of a very particular area, and the fact that it is on fire – how did you make sure that it was recognizably that specific part of the world? 

Oliver Schulz: We started with real world data derived from elevation models. That gave us a pretty good grounding in reality. We got lidar scans for very specific locations like the Pulga Bridges for example which was invaluable as this is usually something one doesn’t get from any publicly available sources. We spent quite a bit of time to get us a very good foundation of all key locations, which meant that everything had a geometrical base until the very last mountain you see on the horizon.

Our Lidar Supervisor David Salamon was instrumental in setting up this base. He used some maps imagery to give a rough base color to all those individual geometries that served as a rough guide later on in layout and surfacing for distributions of materials or assets. One has to keep in mind that most data was post 2018 so for instance vegetation had to be recreated from mostly photographic references shot before the fire. We tried to stay as true as possible to real world geography, but later on of course things had to be changed for storytelling reasons. 

DP: When merging New Mexico plates into your California canyon builds, how did you maintain scale and geological continuity?

Oliver Schulz: As production did not have access or in case of some very sketchy roads didn’t shoot at the original location for safety reasons, they did some scouting through the US and chose some New Mexico locations as stand ins for some of our sequences. The most prominent was the Pulga road for sure. In the film, the first responding firefighters trying to get to the origin of the camp fire first get sight when they are on top of the Pulga Highway bridge crossing the Feather River Canyon.

Without any better option they decide their best shot is to try and get to the fire following a very narrow road on the slope of the canyon. All shots on Pulga Bridge were shot on a Studio Backlot featuring full CG Environments including the FG bridge. This narrow path however was all shot on the New Mexico location with two big fire engines driving a slightly wider road. 

In production that meant that we replaced most of the visible Environment due to a couple of reasons. First of course it needed to have the right roadwidth and the correct canyon in the background. Second we needed to have very windy vegetation everywhere. Third in case all of that worked in camera which was pretty rare we still needed to put FX Elements into every shot consisting of dust, debris, smoke and later also embers. With those guidelines in place probably 90% of the shots became full CG exteriors only keeping small bits of photography for fire engines and some road pieces.

Once all those went into layout we made sure to keep a senseful progression to those shots meaning having the firefighters travel along the road during those shots in cutorder. The topography of the shooting location though was pretty different from the storypoint progression on the pulga road, so was the framing in camera when pointing at the fire from the fire engine interiors.

That of course meant as good and real our base was, it needed to be heavily augmented to make sense with storytelling and framing choices. Most shots feature the correct BG canyon but the midground is totally made up to allow for good view to the fire origin. All of this had to be understandable even with very frenetically moving handheld cameras.

DP: Let’s talk vegetation: How much botanical creative freedom did you have? 

Oliver Schulz: Vegetation was a big part of the environment and one of the reasons for the rapid spread of the fire. All FVX vendors had to tackle it in one way or the other which meant all were contributing to the research for which plant goes where. The foundation was once again the research and material collection from Charlie and his team.

We focused on the most common species found in this region of CA and made sure the level of dryness and the distribution made sense. So in this sense there was not too much freedom here as everyone tried to make this as real as possible from this point of view. For the build we actually just used the most common ground which is Speedtree with some augmentations done in Houdini. Part of the assets were also shares from other vendors which just needed ingestion and rigging in FX.

DP: You mentioned building a hierarchical “ecosystem” in Houdini. How modular was this system, and how much hand-authoring did artists still need to do per shot?

Oliver Schulz: This was something we actually invested a bit of time in at the very beginning and was overseen by CG Supervisor David Schulz and Layout Lead Mareike Loges / Senior Layout Artist Björn Markgraf. The core idea is nothing new and hierarchical just means that you start from the biggest Elements in your kit and than go smaller and smaller based on the previous distribution of Elements. First step is to either scatter or handplace big trees for example, following this you end up with a certain distribution. 

Based on this the system places smaller entities like younger trees or seedlings and smaller shrubs and bushes around or between the big trees. This distribution is based on simple rules like distance or terrain steepness. In case of the Pulga road we divided it up in two categories: mountains and roads. Both had similar procedures. We would always start with the rough blocking geometries matching either scan data, elevation data or sometimes just made up. From there we would generate the base coverage of rock cliffs which would hold out trees mostly in those areas. Following this we created the trees and bigger vegetation which would determine the ground coverage of rocks vs more pepply ground.

Roads were pretty similar but less complex as they mostly feature small stones. Again here we used some manually created maps to drive the distribution of small vs bigger pebbles that mostly accumulate on the side for example.

The toolset itself worked pretty well and as it was applicable as a template we could have a fully laid out shot in a day. Shot specific adjustments were applied on almost every shot though, mostly for continuity, visibility or art direction purpose. 

DP: Vegetation, environment, and FX were all dependent on one another. How did you keep versioning sane between departments?

Oliver Schulz:  That was a big topic indeed and it only is possible with two things: a rigorous approval system and a good pipeline that helps you track those approved layouts. We rely on our usd pipeline to do exactly that for us, it makes it somewhat easy (Im sure layout and production will hit me for this) to track department versioning. For each layout update we`d always get automatic QC renders that run through our inhouse “slapstick” system which is our inhouse auto comp engine.

When Layout would do a specific change it would publish this either on a shot or on an Sequence/Environment level. This will trigger a QC render from the shotcam of the affected shots. Once the rendering is done it will have a postjob that combines it with the prepped plate in nuke and runs another renderjob that will give you the layout reviewable which is than checked and can be approved and pushed into the pipeline from RV. This Layout than becomes available to the FX department which would run all needed simulations and hand off another QC reviewable for approval. Without those systems in place it would have been a nightmare to stay on top of all these versions!

DP: You said the layout department drove wind direction and strength instead of FX. How did that change your creative workflow?

Oliver Schulz: Yes that was indeed true and one of our early conversations we had internally to determine the approach all Environment builds would share. It was a practical decision based on two factors: We would simulate all vegetation on the asset level in different windspeeds for efficiency reasons and we wanted to keep iteration loops to a minimum.

This meant that I wanted to look at layout versions with moving vegetation as the strong directional wind would make it necessary to consider this already while layouting trees. As the direction is clearly visible you cant rely on spinning a tree 360 deg free in Y to create variations as the direction is “baked” in, so you need to see it moving in order to determine if an environment looks good!

The second reason is that FX needed to take care of vegetation simulation only once and when approved never needed to come back. This system worked really well and was accessible to the layout artists down to the single blade of grass, meaning one could really art direct where and how much specific things should move.

DP: You divided smoke into “hero” and “residual” categories. How did you manage density and readability without losing visual clarity?

Oliver Schulz: These two categories were simply based on the fact that we needed to deal with smoke in almost every shot. The ever present residual smoke needed to inherit a direction, needed to be art directable and also needed to render as fast as possible. Its pretty much the equivalent of atmospheric perspective in a wildfire scenario. Our Fx Supervisor Akin Göcmenli came up with a system of instanced presimulated caches that sometimes could consist of thousands of individual ones.

We started by doing simulations of smoke with a constant wind direction and speed that had a hidden source of emission and diffused pretty soon. That gave us a very soft falloff to the edges of the simulation grid which made these simulations perfect to overlap and look as one big single instance of smoke. On top due to those aspects it was quite easy to remove single containers and punch holes into the wall of smoke for visibility. We also invested a bit of time to develop shaders and render efficiencies to cut down on notoriously long volumetric rendertimes for this element.

Hero smoke was the category which either had a visible emission source in frame or simply had a hero storytelling element. These were usually shot or sequence simulations as they were mostly much denser and most of the time also much closer to camera. We also spend a good amount of time matching shading and simulation to real world references.  The secret to readability also lies in relentless QCing of outputs to make sure once you kickoff the expensive lighting renders, you are as certain as possible all elements are going to work. 

DP: The ember work looks incredibly detailed. How did you simulate believable motion in strong winds without visible repetition or looping patterns?

Oliver Schulz: Embers were a big part of the equations so by now you might guess…. Yes we spend a bit of time in asset prep to build some solid foundations. The first thing is of course the driving factor for all fx aspect: the wind.

FX developed hero wind forces that we used to simulate all elements with. A good amount of chaos and variance is key to not run into issues with readable patterns in any simulation. Another factor is collision. Embers will behave a certain way when they collide and thats what we tried to replicate. Also the ground plays a big role especially with the heavier emberclumps that slide over it.

Reality is unbeaten when it comes to little quirks and anomalies especially for something as complex as this. As no one is able to have a ground as detailed as the real world we also sometimes had a collision geometry that had slightly more displacement in order to have more detailed collisions happening. 

DP: Lighting and volumetrics are natural enemies. How did you maintain physically plausible lighting through that much smoke and fire?

Oliver Schulz: That was one of the biggest questions going into this project, considering that what was shot on set sometimes had very little to do with what ended up on screen, especially in terms of atmospherics. The best base for something to look real is to match the real thing. We did so in our asset phase and made sure our shaders and lightrigs were physically plausible, especially the ones only used to develop assets. 

We would match greyballs and reference macbeth charts in order to make sure scene lighting was correct in terms of lightbalancing. Then from there we developed shaders for all aspects.One of the most common issues I see is that volume and surface renders aren’t lookdeved in conjunction. What you end up having to do is to grade surface and volume render differently. This leads to very unrealistic renders very fast because there is no ground truth you can come back to.

We tried to make sure all our shaders worked with each other to have exactly this common base. Also when dealing with dozens of light sources and those issues on top that’s definitely a position you don’t want to be in when time is running…. All volumetrics do have very different properties to them where one of the biggest is how they scatter light. Back to front scattering can take a volume from being ultrabright to consuming all lighting energy and being pitchblack. So once you matched the real thing, use those tools wisely to deviate from there and support the story. 

We tried to always start with a balancing pass usually done still in lighting. This goes to comp as the foundation to do all the finetuning with. Still there was a lot of tuning left for comp and also we needed to break reality more than once to make sure that what you wanted to read in a frame remained readable when tons of smoke and fire went in front. Sometimes we needed to go as far as use the deep data to pull things in and out of the smoke to make them visible. Still the most valuable tool you have is the artist’s eye to determine the sweet spot of good vs real.

DP: You mentioned deep rendering bottlenecks, like OIIO running out of patience with too many AoVs. What exactly went wrong first?

Oliver Schulz: Haha yes that was one of the issues that came when switching to full deep with our renders. That means you have each component of each lightgroup rendered with deep data to put it back together in comp. That resulted in a lot of channels that apparently were too much for OIIO to handle. Thank god that was fixed otherwise I wouldn’t write this story now ;)

DP: Rendering holdouts took up to an hour per frame. Did you develop any automation or optimisation to make deep rendering less painful?

Oliver Schulz: Indeed rendering times for deep holdouts were quite painful and nothing to speed up really. With so many volumetric elements you need to deep hold out everything with everything to make sure its accurate. If you multiply this with the number of separate elements rendered and with the amount of light Aovs times the amount of components you end up with a staggering number of renders.

Plus in the end you need to denoise all frames so the best solution was try to plan out delivery dates as good as possible to have time for all those thousands prerenders to run on the farm. Still our compositing Supervisor Oliver Hohn and Lead Nicolas Burgers had some longer evenings ensuring all renders were there the next morning to be picked up by the compositing Artists.

DP: You used machine-learning depth generators to create deep data from plates. What tools powered that, and how reliable were the results?

Oliver Schulz: We started testing tools quite early in anticipation of very challenging compositing work. DepthAnything v2 was what we ended up using as a default prerender pass. The results were a mixed bag considering the wide range of plates we worked with, although it proved to be valuable to have. Comp remapped the relative value output of the depth passes to absolute values from deep data with help of lidarscans or renders and was able to create some good integration especially with more wispy type of smoke.

For denser smoke and more accurate holdouts especially for actors we still needed to rely on a lot of manual roto for good integration. The AI passes proved to be pretty successful though for fast temp work as you get something going in no time. Issues were mostly the missing good temporal stability and also the lack of precision. 

 DP: Before deploying new tech like ML depth generators or procedural ecosystems, how do you test them safely inside production?

Oliver Schulz: We implemented those during production directly on our project infrastructure, so developed, tested and used simultaneously. 

DP: Were there any spectacular ML depth map failures, like smoke reading as solid or background cliffs collapsing?

Oliver Schulz: Depth popping or lost shapes were the most common ones. But as none of these passes were used without correction in comp I’m sure I haven’t seen all of them!

DP: With so many volumetric layers, how did compositors manage complexity without drowning in passes?

Oliver Schulz: We have standard workflows for loading CG renders into nuke which do provide a basic level of organization. However the more elements you have the bigger the compscripts and we had some good ones for sure!

DP: Fire colouration is tricky. Did you use any spectral rendering or rely purely on LUTs to match on-set lighting and heat distortion?

Oliver Schulz: That is very true.. Luckily production tried to shoot everything with a practical fire which provided a good level of references in camera. If you than try to render as physically plausible as possible and have something in frame that you can match exposure to you are already halfway there. We didn’t use any spectral rendering here and rendered everything through Houdinis Karma in RGB.

DP: You switched to full motion-blur sampling for embers instead of faked streaks. How much did that impact render time, and was it worth it?

Oliver Schulz: Oh that was worth every minute of rendertime.. Real Motionblur for an element which is mainly visible in motionblur is a good investment. Plus the rendertimes weren’t actually that bad and took only a couple of minutes as you are not dealing with an expensive shading as well. The biggest benefit is getting nice curved and very interesting blurs especially with collisions.  The trick actually is to only invest time where its needed and render other elements with less costly settings. Deep compositing allows for it as you are not bound to any holdouts and you can combine differently rendered motion blur without any problems.

DP: How crucial was RiseFlow for distributing simulations and maintaining consistency across all sequences?

Oliver Schulz: We started implementing RiseFlow at the very beginning once we had our initial workflow for distributing elements figured out. The development was done by our Head of Pipeline Paul Schweizer and the implementation on the show was spearheaded by Jonas Sorgenfrei.

It actually is a very versatile framework that we use for a variety of tasks here at Rise. Its a modular node based System that can take arbitrary inputs and execute them in a chained workflow. FX built templates for various scenarios that got exposed variables like wind direction, speed, inputs for collision geometry etc. These could than be varied per shot and sent to the farm for execution. Once all those Sims were done, QC renders were submitted to the Farm and when completed, auto comped in Slapstick.

That meant that one artist could do changes on a big number of shots by adjusting the template and than resimming and rendering them over night. All render elements were deepcomped with our deep plate workflow and reviewed the next morning. This allowed for rapid adjustments and turnarounds which was a very crucial aspect of this fast paced production. 

DP: How did RiseFlow and Slapstick communicate between departments for reviews and dailies?

Oliver Schulz: RiseFlow and Slapstick are two different things really. The point where they communicate is that Riseflow might trigger a farmjob where Slapstick is hooked in as a post process that gets triggered after completion of the render. Slapstick again is a modular node based system implemented in Nuke that allows for a generalized template to be created. These inputs could take for instance all general elements that comp might use to layer a shot like mainplates, rotos, colorcorrections, lensdistortions etc and comp them together. We use Slapstick in all departments to create automatic reviewables for assetbuild like turntables with reference images, lighting slaps,fx slaps and so on.

DP: You’ve called The Lost Bus the toughest matchmove job you’ve ever seen. How did you solve the handheld, wet, low-light camera challenge?

Oliver Schulz: That was a tough one indeed. To solve this it really just comes down to the excellence of all individual artists that created those matchmoves. So there is no magic recipe to get through so many challenging matchmoves…

DP: Greengrass loves long, continuous takes. How did you manage to iterate and render efficiently on such heavy, unbroken shots?

Oliver Schulz: I guess it is really to choose your battles wisely… Invest into a good foundation early on and make sure to be as precise as possible in prep phase. Once the show is running and you are in full delivery mode there is no time to go back and redevelop anything.

Render optimization as much as possible and then relying on everything that was set up in the beginning is key to not have to think about accuracy anymore when you are trying to finish the shots. We did this and it really paid off, though having a couple of long shots with lots of elements to render we never ran into the issue of having to fear a render didn’t get finished in time.

There were some challenging shots for all departments involved but again the prep phase paid off and we managed to deliver everything in time. It’s really a Situation in which the Production team led by Michelle Cullen and Production Manager Androniki Nikolaou outdid themselves by planning and scheduling every milestone in production to make sure we had what we needed to finish shots in time. Of course that also means adjusting and revising this schedule each and every day based on client comments and changes.. It’s a tough job to make sure the whole production runs like a well oiled machine!

DP: Deep compositing only works if all layers align perfectly in space. Did you use diagnostic tools or pure visual QC to verify deep accuracy?

Oliver Schulz: The good thing about deep is that it’s pretty accurate as long as the sampling increments in depth are small enough for certain elements. It’s a game of keeping error thresholds low enough so you don’t pick them up actually. The balancing is precision versus filesize. Surface renders aren’t an issue really as you are dealing with front and backsides of hard surface objects really.

The fun starts with volumetric elements and this is where you need to tweak the settings a bit to make sure you don’t end up having 5GB per frame in volumetric renders. Still frames could grow to well over 1GB on bigger shots with all elements included, so we needed to do some rough calculations beforehand to make sure we weren’t running out of allocated serverspace.

DP: How did you maintain consistency for fire behaviour across sequences? Was there a single reference look, or did it evolve shot by shot?

Oliver Schulz: One of the big topics obviously here as the quality of the fire not only needed to remain consistent but also serve the story in how it behaves. When you look at fires in reality they all have very different qualities to them depending on a ton of external factors like what is burning, where it burns, what is the actual heat it produces and what is the influence of the wind and so on. So yes it’s crucial to pick a reference and not try to incorporate them all. The initial tactic we used was to create asset based fires with all components.

The two types that production defined as assets were “spotfires” and “forestfires”. Pretty generalized in description though mostly divided up by scale. So we took those two types into asset development and created a little scene with them. Forestfire in the background and spotfires in the foreground. This scene actually was the same one we used to lookdev all assets in. So we had a common ground for all assets really and the fx ones were not different.

We picked a general reference we felt was working well for each category and supplemented that with references that production had shot on set. The shot element though were mostly run by gas so wouldnt really emit any smoke but were a general ref in terms of breakup and edge qualities. Also those would come in native resolution where most of the actual refs are cellphone captures of much poorer quality.

So with all those references in place we started matching the fires again in different windspeeds. We tried to also implement all little details especially on the bigger forest fire like flambursts on dry wood, falling burning pieces of wood etc. Once fire was in place we hooked it up with all secondary elements like smoke and embers. We had already pretty robust setups developed for each of them individually so we could already build on a solid foundation using those as a base.

Once this little scene was successfully approved by production to go into shots we splitted out the individual components as assets again. These had all elements attached like smoke emission, ember emission, lots of different masks for heat distortion and were ready to be dropped into shots.

Using this technique we had a very solid foundation of very similar looking and behaving fires. Of course for hero shots we would need to resim those, but with setups in place and our template system it was mostly straightforward. Of course there are shots that need to tell a certain story like a fire coming right at you towards camera. Solving a problem like reading a perspective of a selfilluminating matter coming right towards camera is a different beast though you can’t prep for! This just takes a lot of creativity and trial and error to get right…

DP: What’s the single biggest creative takeaway from The Lost Bus you’d carry into your next show?

Oliver Schulz:  Don’t try to put out all the fires at once….

DP: Which shot makes you proudest or gives you flashbacks?

Oliver Schulz: Oh there are so many good ones really, honestly when I was watching all shots in a row I was so happy about the overall level of quality the team achieved in every aspect. So hard to pick singles but the Embercam full CG shots looked amazing on the big screen and were pretty spectacular… but getting them to the state we delivered them in was quite a journey…

DP: Finally, if you had to redo The Lost Bus from scratch, what would you rebuild first? Vegetation tools, compositing templates, or your caffeine reserves?

Oliver Schulz: Myself :)

The post Rendering the Inferno at RiseFX: The Lost Bus first appeared on DIGITAL PRODUCTION and was written by Bela Beier.

First up, Godot 4.4 integrates the Jolt Physics engine directly into its core. Previously available as an extension, Jolt has been the go-to physics engine for many users since late 2022. While this feature is rigorously tested, it’s currently labeled “experimental.” Developers can enable it in the project settings after consulting the documentation to ensure compatibility with their specific use cases.

Embedded Game Windows

Gone are the days of juggling multiple windows like a circus performer. Godot 4.4 introduces embedded game windows, allowing developers to run the game seamlessly within the editor. This feature is currently supported on Linux, Windows, and Android platforms, with macOS support in the pipeline.

Interactive In-Game Editing

Ever wished you could tweak your game on the fly? Now you can. Godot 4.4’s interactive in-game editing lets developers modify game elements in real-time, even while the game is running or paused. This enhancement streamlines the development process, making it more intuitive and efficient.

Ubershaders

Shader compilation stutter got you down? Enter Ubershaders. These pre-compiled shaders act as fallbacks, eliminating the need to wait for specialized shader pipelines to compile during gameplay. The result? A smoother gaming experience without those pesky pauses.

AgX Tone Mapping

For those striving for a cinematic look, Godot 4.4 introduces AgX tone mapping. Adapted from Blender’s recent adoption of the AgX algorithm, this implementation provides a more filmic rendering, especially effective in handling bright scenes.

Performance Improvements

Under the hood, Godot 4.4 boasts faster load times, reduced stuttering, and streamlined processes. These quality-of-life improvements enhance the overall development experience, making the engine more responsive and efficient.

Before migrating existing projects to Godot 4.4, developers are advised to consult the migration guide to understand any breaking changes.

The post Godot 4.4: The Engine That Could (and Did) first appeared on DIGITAL PRODUCTION and was written by Bela Beier.

In nuce: On 11 July 2022 , we reported on the release of Blender 3.2.1 – and the associated new functions. Now the successor, Blender 3.3, has already entered the beta phase – and is scheduled for release on 7 September this year. Version 3.3 is set to come with new functions and improvements in terms of animation, modelling, rigging pipelines, cycles and the workflows for Grease Pencil and Geometry Nodes. Blender 3.3 should still be in the beta phase up to and including 31 August.

New splash screen: The cosmetic innovations include a new splash screen, which has been embellished thanks to a graphic by art director slash concept artist Piotr Kryński . Piotr works at One Pixel Brush and – unusually for an artist – has a bachelor’s degree in economics.

Click further: All further information on the 3.3 roadmap.

The post Blender 3.3 enters the beta phase first appeared on DIGITAL PRODUCTION and was written by Patrick Poti.

A rough understanding of the evolution of colour correction helps in the evaluation of basegrades. The origins of colour grading as we know it today go back a long way, to the early days of television and cinema. For TV, video signals from television cameras or from a film scanner have always had to be levelled or corrected. The profession of colourist originated in the telecine, where film material was converted into a pleasing video signal.

VideoGrade

The technicians provided the colourist with four basic technical parameters with which he could process the video signal: Lift, Gamma, Gain and Saturation. These are still among the most popular grading tools today. In Baselight, they can be found in the VideoGrade Operator. With Lift, which is sometimes also called Pedestal, the colourist adjusts the black level and with Gain the white level. Experienced Photoshop users will find it easy to visualise the resulting gradation curve: Lift sets the starting point (bottom left) and Gain sets the end point (top right). When working with VideoGrade, these are the most important reference points. Gamma is technically a power function whose only parameter is the exponent. The gamma function determines the curvature of the gradation curve between the two end points.

These three parameters can be adjusted not only for brightness, but for all three colour channels of the video signal (RGB). However, the operator is not usually presented with individual controls for red, green and blue, but one for the brightness signal and a two-dimensional one for the colour component. This results in the basic structure of all grading panels: three spheres, which adjust the colour in two dimensions, and a rotating ring around or next to them for the luma setting. Lift is on the left, gain on the right and gamma in the centre. Colloquially, these three parameters are often referred to as shadows, mid-tones and highlights.

A very popular and solid working method used by video style colourists is to first adjust the black level and white point of the image. This involves balancing all three channels in both black and white just before the clipping points. The brightest point in the image is then pure white, i.e. without a colour cast and with maximum brightness, and the darkest point is pure black. This is often referred to as “clean” black and white. The gamma parameter is then set. This regulates the “airiness” and “heaviness” of the image. In other words, a combination of brightness and contrast. If you want to colour the image, for example, you often do this via the gamma, as black and white then remain “clean”.

Baselight provides two modes for VideoGrade. The standard mode is RGB. In YCbCr mode, the luma channel is processed in isolation. Changes in brightness then have no effect on the colour and saturation of the image. Over time, VideoGrade has also become the most important tool for telecine-style colourists. The colourist manually converts an image from a colour space with a high contrast range, such as log coding, into the output colour space. VideoGrade is therefore now not only applied to images in a video colour space, as originally intended, but also to images in a log colour space.

Lift, Gamm, Gain is probably the most frequently used grading operator in the video sector at present. However, it originates from a time when the handling of specular highlights, for example, was of secondary importance. Burned-out windows or overbright skies were tolerated as long as the faces were recognisable. A soft clip, i.e. a smoother transition to overshoot, is not possible with VideoGrade alone. Over time, video colourists therefore developed various techniques to meet this aesthetic requirement. Gradation curves, luma keys, blend modes or dedicated soft clip operators were used for example.

Another disadvantage becomes apparent in VFX workflows. Contemporary compositing works most realistically in a scene-linear colour space. The pixel values are proportional to the photons on set. Pregrading is nevertheless often helpful so that the basic brightness and white balance are correct and the individual shots in a sequence match each other. Unfortunately, lift, gamma and gain destroy the scene linearity and make VideoGrade unusable for this type of VFX pregrading.

FilmGrade

Long before the telecine colourists, the profession of the film light setter emerged. They influenced the look of a cinema film via the intensity of the copy lights and the chemical processes. With the introduction of the digital intermediate process around the year 2000, the new profession of DI colourist emerged. This person processes cinema images digitally before they are exposed on film material and copied onto print material.

The source material was also usually a film scan. The digital intermediate gradually replaced the analogue intermediate process and thus the creative part of determining the light in the copying plant. Film is the all-determining factor in the DI process, as you can only produce colours that can also be reproduced on film material. The analogue process up to the cinema copy is therefore simulated live in grading using a so-called Film Print Emulation LUT. The obligatory film LUT, which is used in the preview output, means that the image reacts differently to the colourist’s inputs than in telecine or video mode.
The manufacturers have developed new grading tools for DI processing, which are based on analogue light determination with copy lights. In Baselight it is called “FilmGrade”. FilmGrade is designed for processing images in the Cineon-Log colour space. After the colour correction, a conversion to a display colour space takes place, for example classically via a LUT or, since Baselight 4.4, via shaders with truelight colour spaces.

FilmGrade consists of a total of six tools, which are divided into two tabs. The main page consists of Exposure, Contrast and Saturation. The second page consists of Shadows, Midtones and Highlights. All tools offer adjustment options via a ball and a rotating ring. The most important tool is Exposure, which can also be adjusted in RGB copy light steps, so-called printer points, via the blackboard panel. The colourist uses Exposure, also known as Offset in other grading programs, to adjust the brightness and the sphere to adjust the colour of the image. Film-style purists try to work with exposure as much as possible, as this simulates an analogue light setting and the image remains very natural. The contrast in all colour channels and the scene linearity are retained when changing the exposure, for example. Shadows, midtones and highlights do not correspond to lift, gamma and gain, as the individual areas are limited by pivot points. If, for example, the shadows are lifted or coloured using Shadows, this is only done up to a defined point in the curve.

With Lift, on the other hand, the entire image is processed, but the shadows are the strongest. In film workflows, the LAD grey test field approximately in the middle of the curve is the anchor point both for calibration and for the FilmGrade colourist. It was defined by Kodak and is a little darker than 18% medium grey. Full black and white are difficult to determine on film because the curve is very flat. This is why a film-style colourist, unlike a video-style colourist, is not so concerned with achieving 100% white or black. With this concept, a soft clip is already active via the simulation of the print material. The visual impression takes centre stage. This grading concept is therefore more natural than VideoGrade.

There are also fundamental problems with this concept. Although controlling the brightness via Exposure works quite naturally, it is not exactly the same as changing the camera aperture or the ISO value. This is due to the log coding used, which does not define the black level exactly to zero, for example. The detailed reasons are beyond the scope of this article.

FilmGrade is now used not only on Cineon log data, but also on any type of log coding such as LogC from Arri. On the output side, not only film emulations but also modern approaches such as ACES are used. This brings us to future-proofing: log coding can only store a limited dynamic range. The Cineon curve, for example, was no longer sufficient for the high contrast range of the Alexa camera. This is why Arri developed the LogC curve. Future camera generations and HDR displays will require further adjustments, which may involve compromises. This also applies to the VideoGrade operator, which was originally only designed for video signals with a standard dynamic range.

BaseGrade – under the bonnet

The time is ripe for a next-generation colour grading operator. Filmlight uses neither a video signal nor film material as its foundation, but algorithms that are modelled on human perception. The dynamic range is not limited by a technical format such as Rec. 709 or Cineon coding, but is ready for the future characterised by HDR.

BaseGrade works identically in every working colour space and therefore always feels the same to the colourist, regardless of the camera used. However, in addition to a sensible colour setup in the scene settings, this also requires the correct keywording of the material, which is usually done automatically. BaseGrade autonomously converts the image into a linear colour space in which the original brightness ratios of the scene on set prevail, as in linear compositing. The user is not aware of the colour space conversion; the next operator in the stack receives the image in the defined working colour space again.

BaseGrade uses an internal colour model based on Lab, which consists of a pure lightness component L and two colour components a and b. The colour plane spanned by a and b has been distorted by the developers with regard to colour correction so that colour and saturation changes have the same visual effect in all colour areas and work feels more intuitive. Four parameters affect the entire image: Flare, Balance, Contrast and Saturation. In addition to these global parameters, BaseGrade divides the image into brightness zones. This is immediately reminiscent of Ansel Adams’ legendary zone system, which, according to the developers, also served as a source of inspiration.

At first glance, there are few parallels to existing tools in Baselight or comparable video grading software such as Resolve. Raw development in Adobe Lightroom comes closest to working with BaseGrade. However, BaseGrade not only offers brightness controls for each zone, but also colour and saturation. In addition, each zone area can be fine-tuned via pivot and falloff. All exposure settings and pivot points are specified in f-stops. This also comes close to human perception and helps photographers and cameramen to understand them. Stops are also a widely recognised and established unit.

Baselight 5.0 

Users are provided with new builds every few weeks, but now version 5 is finally in the starting blocks. The significance of this release becomes clear when you consider that the last full version jump from 3.O to 4.O was more than seven years ago (2OO9).

Although BaseGrade is the most significant innovation in the upcoming version, it is of course not the only one. For example, the software will be greatly expanded in the finishing area with a dedicated blue/green screen keyer, perspective tracker and warper as well as a grid warper and a paint tool. In the plug-in area, support for the Autodesk Flame matchbox shader format and GPU acceleration for OFX will be added. 

CGI renderings with WSP and normal maps can be relit in Baselight 5 or individual objects can be graded separately. And the powerful colour management has been further developed with a special focus on HDR and has been structured more clearly for the user. DP will be looking at further new features in a future issue. 

The colourist can now give the camera operator direct, meaningful feedback, such as: “I have made the entire image half a stop brighter” or “I have lowered the highlights by one stop”. If a Dailies colourist works with BaseGrade, it is even conceivable that such feedback – like the copy light report in the past – will help the cameraman when working on set. In any case, communication is simplified, especially when the cameraman cannot be physically present during grading.
BaseGrade’s reference point is medium grey, as found on 18% grey cards. The brightness zones are defined from there in f-stops. A correction of three f-stops up or down is the maximum in standard mode and is sufficient. For extreme cases, up to six f-stops can be corrected in “Extended mode”.

User interface

The user interface is based on VideoGrade and FilmGrade. Three main parameters at the top, which are mapped to the three sphere-ring combinations on the blackboard panel. Below this is a visualisation of the current grade as a gradation curve, framed by other parameters such as pivot points. The developers have divided BaseGrade into two tabs. The first page is called Dim/Balance/Light and the second Dark/Balance/Bright. The most important parameter, Balance, is permanently visible and mapped to the centre sphere/ring combination on the blackboard. Flare, Contrast and Saturation are also visible on both sides and can be adjusted via potentiometers. As with all other tools, the colourist can of course adjust everything in the user interface and on the blackboard to suit their individual requirements.

The developers have come up with something special for visualisation using a gradation curve. They superimpose a luma waveform display of the current image over the curve. This means that the colourist can always see which parts of the image he is currently working on and how he should readjust the pivot points if necessary
Pivot points should be readjusted.

Practical test

A little familiarisation time is needed to find your way around. However, the curiosity of having a revolutionary tool at your fingertips makes it easy to get started, after which the results motivate you to continue.
Firstly, the promise of the exact aperture scale is checked. And indeed, increasing the balance by one f-stop is exactly the same as doubling the ISO value in the raw developer. And this applies to all tested cameras from Arri, RED and Sony. The best thing about this is that no raw material is required. For example, if you are working with a mixed ProRes and ArriRAW timeline and all raw shots have been pushed by one f-stop, you can now apply the exact same correction to all shots. A cumbersome switch to the De-Bayer settings is no longer necessary and does not bring any qualitative advantages compared to working with BaseGrade.

Adjusting from shot to shot seems to be another ideal task for the tool. Many colourists divide their grade into a base correction per shot and the creative look. Used as the first layer in the stack, BaseGrade’s scene-linear functionality makes it easier to compensate for exposure differences. Shots with diffuse lens flares, which appear in the image as a raised black, are a common problem when equalising. Even technically high-quality lenses such as the master primes show this effect, especially in scenes with light-coloured backgrounds. If you tried to remove the flare using Lift, for example, the entire image would change and the grade would no longer fit correctly. The flare parameter helps in these cases as it corresponds to optical stray light. If the exposure is basically correct, the differences in the black level can be corrected well using flare.

When copying corrections from shot to shot, the colourist should also pay attention to the flare value and readjust it if necessary. For example, if you copy from a scene with strong stray light, the black in the new shot may be completely washed out. With none of the other controls except Flare can you get it back to a decent level. However, if Flare is set correctly, the black can practically never be crushed. In BaseGrade, the shadows are pressed into a pleasant-looking compression and not clipped hard.

The Saturation slider is also pleasant to use. It is amazing that something as widespread as colour saturation could be improved even further. In direct comparison, BaseGrade behaves visually more evenly than existing implementations. Previously, primary colours such as red, for example, quickly became overweight in the image when saturation was increased. Not so with BaseGrade, the strength of the effect is distributed more evenly across the colour wheel. And the best thing about it is that it works in the same way when desaturating images.

BaseGrade shows its particular strengths through the zone model. The gradation of an image can now be modelled in great detail with just one operator. Previously, this required detailed and sometimes quite fiddly tweaking of the curves in CurveGrade or Keying, but now there is a more intuitive alternative. Extracting detail from a sky normally requires a luminance key on the highlights. With BaseGrade you can get surprisingly far without any secondary correction. Bright is lowered and by raising Light you can tease out the last details until just before clipping. If you initially set the correction too high, it is easier to find the right pivot points. You can then reduce to a realistic level.

If the colourist opts for extremely strong corrections, there is a risk of unsightly effects, a preliminary stage of solarisation, so to speak. Although BaseGrade prevents true solarisation, i.e. negative gradients in the gradation curve, the colourist can flatten the curve so much that the drawing is ruined in certain brightness zones. In these cases, a larger falloff, the transition area of the zone, usually provides a remedy, but at the same time reduces the effect slightly.

BaseGrade can also be convincing with a common technique in colour correction. Cross process toning is a popular stylistic device that makes images more interesting in terms of colour. This involves colouring the highlights and shadows in different shades. Complementary colours are often chosen for this: the shadows, for example, in cold turquoise blue and the highlights in warm orange. Colourists often use HLS keys so that they have better control over the effect. With BaseGrade and its zone model, you can precisely control the strength and colour tone of the effect. This will probably save a few layers in the timeline in the future.

On the subject of VFX pregrading: Flare is an artefact that occurs in the camera optics and distorts the scene linearity. With the help of BaseGrade, the real brightness conditions on set can be reconstructed using a correctly set flare value. Afterwards, Balance is used for complete scene-linear colour correction. The flare correction makes BaseGrade more suitable for scene-linear pre-grading than Exposure/Printer-Lights in FilmGrade.

Conclusion

BaseGrade is powerful, but also complex. A properly set up project is the be-all and end-all for correct functioning. If the colour spaces are not correct, it will not work properly. It is advisable to familiarise yourself with the tool slowly at first and then integrate it into your daily work bit by bit. A good way to start, for example, would be to make all saturation corrections with BaseGrade. The next step would be to use it for basic corrections from shot to shot, and so on.

The new grading concept could also be a good introduction to moving image colour correction for photographers with Lightroom experience and, thanks to the intuitive and aperture-based approach, also for cameramen.
The first few days with BaseGrade were very promising: the tool has the potential to create both more natural and possibly completely new looks. It also makes day-to-day work easier. The decisive factor will be how well it is accepted by users.

The post BaseGrade and the evolution of colour grading first appeared on DIGITAL PRODUCTION and was written by Bela Beier.