Physics-based Technicolor 3-Strip (Process IV) Emulation

[Naveen Chandran]

Hi everyone,

I’m a developer working on the color science side of post-production, and I’m looking for some feedback from cinematographers on a tool I’ve been building.

I’ve been trying to accurately reconstruct the Technicolor 3-Strip (Process IV) look in DaVinci Resolve as a DCTL Tool. I found that standard LUTs and RGB curves completely fail to capture how those vintage cameras actually responded to light, so I decided to build a mathematical model of the physical pipeline instead.

I’ve created a DCTL that simulates the original photochemical process from capture to print. I’d love for anyone who frequently shoots or lights for vintage looks to throw some challenging footage at it and tell me how it responds to your exposure.

Here is a quick breakdown of what the math is actually doing under the hood:

• The Camera Capture: It un-mixes the broad spectral overlap of modern digital sensors to approximate what light looked like passing through the original narrow-band Wratten #25, #58, and #47 filters inside the 3-strip prism.

• Subtractive Density: Instead of digital saturation (where colors get brighter), it uses the Beer-Lambert Law to simulate physical CMY dye absorption. If you push the saturation of a color, it physically gets denser/darker, just like a real imbibition print.

• Optical Scatter: It uses true Laplacian blur kernels for the light scatter/halation, rather than standard digital Gaussian blurs.

I have a fully functional demo available, as well as a comprehensive PDF manual breaking down the history and physics of the camera and printer mechanics: https://nxcolor.com/3-strip

I’m really curious to hear your thoughts on how this handles skin tones under different lighting temperatures, and if the halation/scatter feels optically authentic to you. Any technical critique is incredibly welcome!

Thanks, Naveen

[David Mullen ASC]

The tricky thing is that the 3-strip camera used a prism to split light through a green and magenta filter, the green light going to panchromatic stock.

The magenta light went to a blue-sensitive stock that had no anti-halation backing and was dyed red, and placed in front of panchromatic stock. The blue-sensitive stock only responded to the blue wavelengths in the magenta light and then was filtered by the dyed base to send only red wavelengths to the panchromatic stock, which was somewhat soft as a result.

So the red record was always softer and a bit grainier which affected skin tones since they have more red in them.

The red & blue records picked up a magenta flare from the lack of an anti-halation backing in the blue record.

In 1951, Technicolor altered the camera system to become tungsten-balanced, by replacing the gold-flecked prism with a silver coating, and probably by making the blue sensitive stock faster in some manner.

 

 

[John Rizzo]

Hello Naveen

 

we tried your demo and it crashes our GPU  (we are running it a MAC PRO WITH 4 GPU s .

 

regards

[Naveen Chandran]

Hello John,

Which version of Resolve are you running?

Also I've tested on mac Silicon (Metal) and Windows (CUDA and OpenCL), does it show any compilation error dialogs or does it just crash?

Best Regards,

Naveen

[Naveen Chandran]

Just a quick update on this — I’ve released v2 of the tool.

A fair bit has changed since I first posted here. I spent some time refining how the dye transfer stage behaves, particularly the interaction between layers as the gelatin loads up, and also reworked parts of the bipack/halation side to get something that holds together better under exposure.

I’ve also added broader input support so it can be used earlier in the pipeline without needing conversion.

And the tool itself is here (demo available):
https://nxcolor.com/3-strip/

Would be interested to hear any thoughts.

What's New in V2:

Expanded Input Format — Replaces Input Encoding with a new Input Format selector covering 15 camera color spaces including ARRI LogC3/LogC4, Sony S-Log3, Canon C-Log 2, RED Log3G10, Panasonic V-Log, and more. Gamut conversion is handled automatically.
Wide-Gamut Rendering Fix — In v1.1, DaVinci Intermediate and ACEScct inputs were decoded from their log encoding but their wide-gamut primaries were never converted to Rec.709 — colors were systematically wrong for both scene-referred formats. v2 adds correct gamut matrices for all 15 input formats, applied in linear light before tone mapping. Spatial effects now process in the correct domain for scene-referred footage.
IB Print Acutance — New pre-dye sharpening stage that recreates the three-dimensional pop characteristic of original imbibition prints. Adds edge snap and midtone depth before dye processing.
Gelatin Softness — Simulates the resolution limit of the physical gelatin matrix — softening fine surface texture like skin and fabric while leaving edges intact. The diffuse quality unique to real IB prints.
New Dye Physics — Adds Density Coupling and Midtone Dye Boost. Together these model how real dye-transfer color behaves: saturation darkens rather than blooms, midtones carry the richest dye, and highlights desaturate gracefully.
Refined Grain Engine — Improved IB dye grain with smoother large-scale modulation, a new long-range density variation layer, corrected dye-pool skew, and softer reticulation. Re-tuned defaults better reflect the coarser, organic texture of real IB prints.
Major Performance Upgrade — All convolution cores rewritten for significantly faster processing. Approximately 5× faster at 4K on wide-gamut inputs. Halation and bloom now scale correctly to full slider range at any resolution.
Cleaner UI — Redundant enable/disable toggles removed throughout. Several controls consolidated into the new dye physics system.

[Naveen Chandran]

Just another quick update to this thread.

Nx 3-Strip has come a long way since I originally posted this.
 

It is now available as a native plugin for:

• DaVinci Resolve (OpenFX)
• Adobe Premiere Pro
• Adobe After Effects
• Final Cut Pro

So it’s no longer limited to the Resolve DCTL version. It works on both Windows and macOS.

The underlying goal is still the same, recreating the Technicolor Process IV look as faithfully as possible, but now as a proper native plugin across the main platforms.

Thanks to everyone who tried the earlier version and gave feedback. A lot of that feedback went into the new version.

More info here:
https://nxcolor.com/3-strip/

[Aristeidis Tyropolis]

I appreciate the effort taken but looks nothing like Technicolor.

[Naveen Chandran]

11 minutes ago, Aristeidis Tyropolis said:

I appreciate the effort taken but looks nothing like Technicolor.

Thanks, I appreciate the honest feedback. If you have a particular Technicolor reference you're comparing it against, I'd be genuinely interested to see it. It would definitely help me improve the tool.

Is there anything specific that feels off to you — the grain, colors, contrast, or something else?

Edited August 13 by Naveen Chandran

[Aristeidis Tyropolis]

Look at this:

And look at what you posted - which is I presume some A.I video + the plugin.

One is a process that starts within the camera and then the photochemical process that happens afterwards - yours is a plugin that sits on "top" on some video.

They will never look alike.

I actually think that if you feed clips and/or images for training to modern A.I tools and then some "other" clips the result will be pretty much consistent but obviously not original.

There, it's a lot gibberish talk but took me five minutes and was created locally using Minimax H3.

 

In other words you need all ingredients to make a soup.

 

[David Mullen ASC]

"Rear Window" was shot in Eastmancolor, not 3-strip Technicolor

[Aristeidis Tyropolis]

Ah - haha, my mistake was confused by:

[David Mullen ASC]

That means the prints were Technicolor dye transfer.

[Robert Harris]

On 8/13/2026 at 4:06 PM, David Mullen ASC said:

That means the prints were Technicolor dye transfer.

Hi, David. I was about to bring that up. The “Color by Technicolor” verbiage had nothing to do with dye transfer. It merely made the point that original color prints were struck by the Technicolor lab.

For dye transfer printing the credits generally read either “Technicolor,” or “in Technicolor.”

All original prints of Rear Window by Tech in 1953 were via direct positive to Eastman stock. It was not until the 1962 re-issue that dye transfer prints were produced.

in 2000 we did a limited run of dye transfer based upon matrices derived from our restored dupe neg.

RAH

Edited August 28 by Robert Harris

[Robert Harris]

On 8/13/2026 at 10:10 AM, Naveen Chandran said:

Thanks, I appreciate the honest feedback. If you have a particular Technicolor reference you're comparing it against, I'd be genuinely interested to see it. It would definitely help me improve the tool.

Is there anything specific that feels off to you — the grain, colors, contrast, or something else?

If the intent is to truly replicate the Technicolor look, first thing that must go is resolution. Technicolor was never sharp. Keep in mind that it was three b/w negs with three layers of grain. Reproduced today via 4k scans of OCNs, with beautiful work performed by WB’s MPI, the resultant image must be de-grained, which then leaves an image appearing akin to Technicolor, but with a higher resolution than would ever have been seen when printed via imbibition from matrices with metal dyes.

What gave Technicolor dye transfer prints a feeling of sharpness in projection was its contrast levels. There was no sharpness in the image.

The other part of three-strip cinematography to keep in mind is that it was extremely dependent upon production color design. Take a look at the earliest demo work - La Cucaracha and Becky Sharp, and you’ll see an overabundance of pure yellows, cyans and magentas.

Even after the process took on a more natural look, see Quiet Man examples above, it still was very color dependent.

Please keep in mind that I’m referring only to three-strip and not printing based upon Eastman originals.

If you need a copy of Becky Sharp - albeit digital - I’ll be happy to send you a proxy.

RAH 

[Jeff Bernstein]

[Aristeidis Tyropolis]

4 hours ago, Robert Harris said:

For dye transfer printing the credits generally read either “Technicolor,” or “in Technicolor.”

Thanks Robert! Interesting and not confusing at all!

[David Mullen ASC]

On 3/27/2026 at 2:11 AM, Naveen Chandran said:

 

Here is a quick breakdown of what the math is actually doing under the hood:

• The Camera Capture: It un-mixes the broad spectral overlap of modern digital sensors to approximate what light looked like passing through the original narrow-band Wratten #25, #58, and #47 filters inside the 3-strip prism.

I've been curious if there is a meter to measure the wavelength range of a color filter so I could try it out on the Technicolor camera at the ASC... I think Josh Pines measured it when he did the D.I. for "The Aviator" but...

The problem again is that the prism did not use three filters -- it used two, a green and a magenta.

The magenta light hit a blue-sensitive stock that was dyed red to act as a filter for the panchromatic stock behind it. So you'd need to know: (1) the spectral transmission of the magenta filter; (2) the wavelength sensitivity range of the blue-sensitive emulsion, (3) the spectral transmission of the red dye used on the blue-sensitive stock.

[David Mullen ASC]

The early 3-strip Technicolor movies tested like crazy in pre-production -- every fabric, wall color, make-up -- so the colors you see are what they wanted to achieve.

[Robert Harris]

1 minute ago, David Mullen ASC said:

The early 3-strip Technicolor movies tested like crazy in pre-production -- every fabric, wall color, make-up -- so the colors you see are what they wanted to achieve.

I'm not seeing the tech replicated by a plug-in...