Help converting formula to RPN (LogC4 <> Linear)

groucho86 · 16th February 2023, 00:23

Hello! Is anyone able to translate to RPN/Expr ARRI's LogC4 to Linear and Linear to LogC4 formulas found here?
https://www.arri.com/resource/blob/2...ation-data.pdf (page 9 under 'Reference CTL Implementation')

Thanks in advance!

Selur · 16th February 2023, 15:21

No, not sure whether it helps, but https://www.arri.com/en/learn-help/l.../lut-generator has a link with a 3D LUT Package for LogC4.

groucho86 · 16th February 2023, 15:51

Thanks Selur, but a LUT cannot handle values out of 0.0-1.0 range, so it needs to be formula-based.

Julek · 16th February 2023, 21:59

I rewrote the example on page 10 to Expr here: https://gist.github.com/dnjulek/58a2...929fd9ce151eca

groucho86 · 16th February 2023, 22:13

Quote:

Originally Posted by Julek

I rewrote the example on page 10 to Expr here: https://gist.github.com/dnjulek/58a2...929fd9ce151eca

Much appreciated Julek! Will compare against Resolve's implementation asap.

16th February 2023, 00:23	#1 \| Link
groucho86 Registered User Join Date: Apr 2016 Posts: 85	Help converting formula to RPN (LogC4 <> Linear) Hello! Is anyone able to translate to RPN/Expr ARRI's LogC4 to Linear and Linear to LogC4 formulas found here? https://www.arri.com/resource/blob/2...ation-data.pdf (page 9 under 'Reference CTL Implementation') Thanks in advance!

16th February 2023, 15:21	#2 \| Link
Selur Registered User Join Date: Oct 2001 Location: Germany Posts: 7,277	No, not sure whether it helps, but https://www.arri.com/en/learn-help/l.../lut-generator has a link with a 3D LUT Package for LogC4. __________________ Hybrid here in the forum, homepage

16th February 2023, 21:59	#4 \| Link
Julek Registered User Join Date: Dec 2020 Posts: 88	I rewrote the example on page 10 to Expr here: https://gist.github.com/dnjulek/58a2...929fd9ce151eca __________________ CPU: AMD 3700X \| GPU: RTX 3070Ti \| RAM: 32GB 3200MHz GitHub

16th February 2023, 15:51	#3 \| Link
groucho86 Registered User Join Date: Apr 2016 Posts: 85	Thanks Selur, but a LUT cannot handle values out of 0.0-1.0 range, so it needs to be formula-based.