RawTherapee processing challenge

The aim of this challenge is twofold: a) to allow you to familiarise yourself with Cam16 and the tools that have been integrated into the Local Adjustments “Color appearance (CAM16 & JzCzHz)” module. b) to validate the changes before merging into “dev".

For this reason the images should be processed for tonality and color primarily using the local adjustments “Color appearance (CAM16 & JzCzHz)” tool in the lacam16n development branch.

You can find the executables here:

You can also use the Abstract Profile tool in the Color Tab, bearing in mind that this is virtually identical to the equivalent local adjustments tool. The main differences are:

a) the position in the pipeline,

b) the local adjustments tool is integrated directly into Ciecam, whereas the Color Tab equivalent is not,

c) the local adjustments tool allows you to use the possibilities inherent in Local Adjustments such as deltaE detection, multiple spots, excluding spots etc. As a reminder, the local-adjustment tool can also be used globally by setting the Scope slider to its maximum value.

You may of course use other tools in Local Adjustments tools to complement the “Color appearance (CAM16 & JzCzHz)” tool (e.g. Blur/Grain & Denoise); nothing is forbidden, as long as you only use RT.

I have chosen five images mostly from previous Play Raws as shown in the following thumbnails and will post the corresponding raw files at roughly one-week intervals starting with Image_0080.CR2:

All these images are “Creative Common Attribution-share Alike 4.0”.
Raw File

2010_MONTR_033.NEF (The blue horse)




Please post your results in this thread.

The challenge winner for each of the images will be the one that receives the most likes. :grinning:

You can find additional information on Pixls.us :

  • News from Cam16 - A processing challenge is coming-up

  • Another tutorial - Color appearance - Truck under a tunnel

  • Is Rawtherapee complex

  • Scene-referred and Display-referred (part 1, part 2, part 3)

  • Paris Olympic Games - Pont Alexandre III – Tutorial

And in Rawpedia :https://rawpedia.rawtherapee.com/Local_Adjustments#Using_the_Cam16_and_HDR_functions

Thanks for your help



For confirmation, the first image IMG_0080.CR2 and the first link.

Raw File

It may be necessary to clean the cache (or use neutral). Because following the malfunctions found by @paulmatth and @Silvio_Grosso , and the reports that Wayne @Wayne_Sutton made to me, certain functions have been rewritten. But maybe it’s not necessary?

Thank you.


With RT 5.10-458_lacam16n_

20240318-desafioRT1-IMG_0080.jpg.out.pp3 (21,4 KB)



Thank you for being the first to participate :+1:



IMG_0080-1.jpg.out.pp3 (17.3 KB)


Thank you :wink:

Hello and thank you all.

I won’t pass judgement on every image presented, I don’t think that’s my role. I’ll let users evaluate and personally see how “someone else” approaches the problem.

After a week or two (or more, or less), I’ll make a summary and comparative assessment of the various ways of approaching each image, remaining anonymous.
This will build up a collective feedback from which everyone can benefit.
I don’t know yet what form this will take, but maybe I’ll put it on Rawpedia - to make sure I can keep track of it. Perhaps I’ll ask each of the participants to write a brief text of a few lines - if of course he accepts, explaining “why these choices?”



1 Like

With Version RawTherapee_Beep6581_lacam16n_win64. Didn’t want to saturate beyond a point. Stayed mainly with the Colour Appearance - CAM16 module

IMG_0080.CR2.pp3 (15.5 KB)

1 Like

Thank you :wink:



I fixed a major bug, which caused a crash when you “delete” a spot.

I made 2 improvements

  1. Cam16 - “Smooth highlights” in “Source Data Adjustments” (with a combobox - old choice and another algorithm)
  2. Ciecam - Advanced Tab - best behavior of “temperature” in “Viewing conditions” (GUI problem)


Have a good evening


1 Like

lacam16n branch / macOS

IMG_0080.jpg.out.pp3 (60.2 KB)
This image shows several local adjustment areas using Color Adjustments CAM16 tools as gradient and iterative tests.
The upper two are duplicate spots. The lower left series are also duplicative and overlain, as are the two slug things on the lower right.

1 Like

Blue Horse lacam16n

blue_horse.jpg.out.pp3 (169.1 KB)

Several CAM16 spot spots were used to highlight Horse.
Some light blurring spots were added to the street and background, except the red street signs, in order to tone down the non-foreground textures.
Finally, Blue Horse was unblued with a Color Appearance CAM16 spot.

Newbigging by David Oliver, doliver.co.uk

IMGP2426.jpg.out.pp3 (29.6 KB)

Light and color improvements using three zones with the CAM16 local adjustment spots.

1 Like

RT lacam16n
Ballet dancers by stefan.chirila

S7_00463.jpg.out.pp3 (39.8 KB)

Ballet Dancers illuminated by several CAM16 local adjustment spots as if spotlights.

“Bee Ding” by Micha

B-1.jpg.out.pp3 (49.7 KB)

Overall boosts in lightness and contrast; a spot with CAM16 lightness set all the way down to black out the green tarp.

BTW @jdc I noticed Contrast Threshold (J & Q) will clip from black to white if you raise it too high with a sufficiently high Contrast level.

PS @jdc Sorry I jumped the gun on your whole “one week interval” idea…

PPS @ jdc Overall these CAM tools seem to work at a better dynamic range than other of the CAM16 implementations. I could easily process an entire photo using mostly only the local CAM16 spots.


Hello Richard,
I am pleased that you are using my picture here. But I still haven’t quite understood what you want to show with it. I’m already very curious.

IMG_0080.jpg.out.pp3 (24.2 KB)

(sloppy noise reduction but was time limited)

1 Like

We are testing an experimental change in RawTherapee in this thread, of which @jdc is the author.

In my example I have processed the photo using these local adjustment zones with the Color Appearance, CAM16 tools there.

IMGP2426-2.jpg.out.pp3 (18.1 KB)

blue_horse (1).jpg.out.pp3 (20.5 KB)

S7_00463.jpg.out.pp3 (20.5 KB)

Hello everyone and many thanks for your contributions. :+1:
@HIRAM @priort

With the time difference, it’s a bit difficult to communicate. Let me remind you of the origin of this post
"The aim of this challenge is twofold: a) to allow you to familiarise yourself with Cam16 and the tools that have been integrated into the Local Adjustments “Color appearance (CAM16 & JzCzHz)” module. b) to validate the changes before merging into “dev".

I’ve chosen these 5 images because they all present a specific difficult character: high DR, noise, deep shadows, high contrast between background and center of the image, colorimetry, etc.
Of course they’re well known, and that’s one of the reasons we chose them.

I’d like to create a collective Feedback Report so that users have several ways of processing an image at their disposal. I don’t yet know what form this will take, but it presupposes that I include in a document :

  • the basic image (e.g. IMG_0080.CR2),
  • the various pp3, a summary of the processing,
  • and if possible a short text from the author describing “why he did it that way ?”.

In order to allow the same amount of time to work on each image, I suggested processing one per week, which would also make it easier for me to provide feedback.

But that doesn’t matter, and as Pierre de Coubertin, who organized the first modern Olympic Games, would say : “L’essentiel est de participer”.

If you can this week on the first image (IMG_0080.CR2) that would be preferable, but I’d rather have a messy participation than no participation.

Thank you again. :grinning: