darktable ep 082 - Color Calibration module (pt 1 of 2 - channel mixer)

Summary

In episode 82 of 'Understanding Darktable', the focus is on the new color calibration module in Darktable 3.4, which replaces the deprecated channel mixer and supplements the legacy white balance module. The video explains the module's dual role and its settings, including the auto-apply chromatic adaptation defaults in preferences. It covers the use of color calibration as a channel mixer, detailing the interface updates, the concept of camera reference (D65), and the process of adjusting color channels for various effects. The episode also touches on presets for monochrome mixes, suggesting they provide a more accurate representation of film stocks. Part two will explore the module's use as a white balance supplement.

Takeaways

• 🔄 Darktable 3.4 introduces a new module called 'Color Calibration' which replaces the deprecated 'Channel Mixer' module and supplements the 'Legacy White Balance' module.
• 🎨 The 'Color Calibration' module has two functionalities: as a replacement for the 'Channel Mixer' and as an addition to the 'Legacy White Balance'.
• 🛠 In the preferences, there's a new setting 'Auto Apply Chromatic Adaptation Defaults' which can be set to 'Legacy' or 'Modern', affecting how the 'Color Calibration' module is used upon importing or resetting images.
• 📸 The 'Legacy' setting applies the 'Legacy White Balance' module as usual, while 'Modern' activates the 'Color Calibration' module with a 'Camera Reference' setting, typically D65.
• 📚 The script suggests further reading on photo.net for those interested in the technical aspects of illuminance and chromatic adaptation.
• 🔄 The 'Color Calibration' module operates differently from the old 'Channel Mixer' by working in an unbounded color space, offering more flexibility with tones, colors, and hues.
• 🎛 The module features tabs for each color channel (R, G, B), allowing for adjustment of the output based on the input from other channels.
• 🌈 The 'Colorfulness' tab lets users adjust the intensity of the color channels, either accentuating or attenuating the effects made on the R, G, and B tabs.
• 🔆 The 'Brightness' tab alters the luminosity of each color channel, with options to make them darker or brighter.
• ⚫ The 'Gray' tab is used for creating monochrome mixes from color images, offering a way to blend primary channels into a black and white result.
• 📚 New presets for black and white film stocks have been created by Aurélien for the 'Color Calibration' module, which are believed to be more accurate than the old presets.

Q & A

What is the new module in Darktable 3.4 called?

The new module in Darktable 3.4 is called 'Color Calibration'.

What are the two main functions of the Color Calibration module?

The Color Calibration module serves two main functions: it replaces the deprecated Channel Mixer module and acts as a supplement to the legacy White Balance module.

What is the 'auto apply chromatic adaptation' setting in Darktable preferences?

The 'auto apply chromatic adaptation' setting in Darktable preferences determines the default behavior for the Color Calibration module when importing a new image or resetting the history stack. It can be set to 'legacy' or 'modern'.

What does setting the 'auto apply chromatic adaptation' to 'legacy' do?

Setting the 'auto apply chromatic adaptation' to 'legacy' means that the legacy White Balance module will be applied as usual, defaulting to the white balance set in the camera at the time of exposure, and the Color Calibration module will not be added to the list of active modules.

What happens when the 'auto apply chromatic adaptation' is set to 'modern'?

When set to 'modern', the legacy White Balance module is set to 'camera reference' (usually D65), and the Color Calibration module is activated by default for all processing.

What does the 'Camera reference' setting in the White Balance module refer to?

The 'Camera reference' setting in the White Balance module refers to a standard illuminant, usually D65, which is used as a reference point for white balance.

How does the Color Calibration module differ from the old Channel Mixer module?

The Color Calibration module works in an unbounded color space throughout its part of the pixel pipe, allowing for more tones, colors, and hues to work with, unlike the old Channel Mixer which was assumed to work in an sRGB color space all the time.

What is the purpose of the 'Chromatic Adaptation Transform' tab in the Color Calibration module?

The 'Chromatic Adaptation Transform' tab in the Color Calibration module is used to set the adaptation to none, essentially turning off this tab and removing all options except for the gamut compression when using the module as a channel mixer.

What does the 'Colorfulness' tab in the Color Calibration module allow you to do?

The 'Colorfulness' tab allows you to accentuate or attenuate the intensity of any adjustments made on the R, G, and B tabs.

What is the 'Brightness' tab used for in the Color Calibration module?

The 'Brightness' tab in the Color Calibration module is used to alter the intensity or luminosity of each of the red, green, and blue channels.

How can you create a monochrome mix of a color image using the Color Calibration module?

You can create a monochrome mix of a color image by adjusting the sliders in the 'Gray' tab of the Color Calibration module to decide how much of each of the three primary channels you want to introduce into your monochrome mix.

What are the presets in the Color Calibration module for monochrome mixes based on?

The presets in the Color Calibration module for monochrome mixes are based on film stocks, and they are designed to be more representative of the film stocks they are named after, according to the creator of the presets, Aurelian.

Why was the old Channel Mixer module deprecated in Darktable?

The old Channel Mixer module was deprecated because it was assumed to work in an sRGB color space all the time, which is not necessarily the case in modern photography. The new Color Calibration module offers more flexibility by working in an unbounded color space.

How can you access the deprecated Channel Mixer module if you still want to use it?

You can access the deprecated Channel Mixer module through the 'Modules Presets' window in Darktable, where there is a preset of grouped modules for deprecated modules.

Outlines

00:00

📚 Introduction to Darktable 3.4's Color Calibration Module

The video script introduces a new module in Darktable 3.4 called 'Color Calibration,' which serves dual purposes. It replaces the deprecated 'Channel Mixer' module and also complements the 'Legacy White Balance' module. The tutorial is split into two parts, with this first part focusing on using the new module as a channel mixer. The script also revisits the 'auto apply chromatic adaptation defaults' setting in preferences, explaining the 'legacy' and 'modern' options and their impact on image processing. The presenter sets the module to 'modern' for all processing, demonstrating the updated user interface for the white balance module and explaining the 'Camera Reference' setting, which is typically set to D65, a standard for daylight illumination.

05:01

🎨 Exploring the Color Calibration Module as a Channel Mixer

This section delves into using the Color Calibration module as a replacement for the old Channel Mixer. The module operates in an unbounded color space, offering more flexibility in color and tone adjustments than the deprecated Channel Mixer, which was limited to the sRGB color space. The presenter explains the functionality of the R, G, and B tabs, which control the output of the respective color channels, and how to adjust them to create custom mixes. Additionally, the 'Colorfulness' tab is introduced, which allows for accentuating or attenuating the intensity of the color channels. The 'Normalized Channels' checkbox is explained, which ensures consistent output saturation regardless of the input values. The summary also touches on the 'Brightness' tab for adjusting the luminosity of each channel and the 'Gray' tab for creating monochrome mixes, mentioning the new presets designed to better emulate film stocks.

10:03

🖤 Transitioning from Old Channel Mixer to the New Color Calibration Module

The final paragraph discusses the transition from the old Channel Mixer module to the new Color Calibration module. It mentions that the old module has been deprecated and is no longer readily available in the Darktable UI, but can still be accessed through a 'grouped modules for deprecated modules' preset if needed. The presenter recommends using the new Color Calibration module for channel mixing tasks moving forward. The video script concludes by previewing the next episode, which will cover using the Color Calibration module as a supplement to the Legacy White Balance module.

Keywords

💡Color Calibration Module

The Color Calibration Module in Darktable 3.4 is a new feature that serves dual roles: replacing the deprecated Channel Mixer Module and supplementing the legacy White Balance Module. It is central to the video's theme as it is the primary subject being explained and demonstrated. The module allows for advanced color adjustments and is used throughout the script to illustrate its replacement of older functionalities and its integration with new features like the 'camera reference' white balance setting.

💡Channel Mixer

The Channel Mixer is a feature that was previously used in Darktable for color adjustments but has now been deprecated in favor of the new Color Calibration Module. It is mentioned in the script to highlight the transition to the new module, which is more versatile and works in an unbounded color space. The term is used to compare the old and new methods of color adjustment, emphasizing the improvements in the latest version of Darktable.

💡White Balance

White Balance is a fundamental concept in photography and photo editing, adjusting the image so that white appears truly white under any lighting condition. In the script, it is discussed in the context of the new Color Calibration Module and the legacy White Balance Module. The video explains how the new module can be used as a supplement to the legacy module, and how the 'camera reference' or D65 setting impacts the white balance.

💡Chromatic Adaptation Transform

Chromatic Adaptation Transform is a technical term used within the Color Calibration Module to describe the process of adjusting colors from one color space to another. In the script, it is mentioned as part of the module's functionality, particularly when the adaptation is set to 'none', which effectively turns off this feature and allows the module to function as a Channel Mixer.

💡Camera Reference

Camera Reference, specifically D65, is a standard for white point in digital imaging, representing daylight under overcast skies. In the video script, it is discussed as a new setting in the White Balance Module when the 'modern' option is selected in preferences. It is used to standardize the white balance across images, which is crucial for consistent color representation.

💡Scene Referred Workflow

Scene Referred Workflow is a color management approach that deals with colors in relation to the scene's lighting rather than the output device. The script mentions it as being set in preferences and being automatically activated alongside the Color Calibration Module, indicating its importance in the new version of Darktable for maintaining color integrity throughout the editing process.

💡Filmic and Exposure

Filmic and Exposure are modules in Darktable that simulate the way film responds to light and adjust the exposure of an image. The script refers to them as being set to active by default when using a Scene Referred Workflow, indicating their role in enhancing the look of images to mimic film photography.

💡Monochrome Mix

Monochrome Mix refers to the process of creating black and white images by blending different color channels. In the script, it is discussed in the context of the Color Calibration Module's 'gray tab', where sliders are adjusted to create a monochrome mix from a color image, emulating different film stocks.

💡Presets

Presets in photo editing are pre-defined settings that can be applied to images for quick adjustments. The script mentions new presets created for the Color Calibration Module, which are designed to emulate different black and white film stocks more accurately than the previous Channel Mixer presets.

💡Normalized Channels

Normalized Channels is a feature in the Color Calibration Module that ensures the output saturation is consistent with the input saturation by adjusting the values of the red, green, and blue sliders so that they sum up to one. It is mentioned in the script as a way to maintain color balance while making individual channel adjustments.

💡UI Refresh

UI Refresh refers to updates made to the user interface of a software application. In the context of the script, it describes the updated design of the White Balance Module in Darktable 3.4, making it more user-friendly and visually distinct with new icons and options.

Highlights

Darktable 3.4 introduces a new module called 'Color Calibration' with two distinct functionalities.

The Color Calibration module replaces the deprecated 'Channel Mixer' module.

It also serves as a supplement to the 'Legacy White Balance' module.

A new preference setting 'Auto Apply Chromatic Adaptation Defaults' is introduced for the Color Calibration module.

The 'Legacy' option in preferences will apply the Legacy White Balance module and not activate the Color Calibration module.

Choosing 'Modern' in preferences will activate the Color Calibration module and set the Legacy White Balance to 'Camera Reference'.

The 'Camera Reference' setting is typically set to D65, a standard for illuminance in photography.

The Color Calibration module can be used as a Channel Mixer by setting the adaptation to 'None'.

The module provides an unbounded color space, offering more tones, colors, and hues to work with compared to the old Channel Mixer.

Each color channel (R, G, B) can be independently adjusted to create custom mixes.

The 'Colorfulness' tab allows for accentuation or attenuation of the intensity of the color channels.

The 'Brightness' tab adjusts the luminosity of each color channel.

The 'Gray' tab is used for creating monochrome mixes from color images.

Aurelian has created new presets for the Color Calibration module that are more representative of film stocks.

The old Channel Mixer module can still be accessed through the 'Modules Presets' window for those who prefer it.

The Color Calibration module is recommended over the old Channel Mixer for current use.

The next episode will cover using the Color Calibration module as a supplement to the Legacy White Balance module.

Transcripts

dark table 3.4 has a new module called

color calibration and there's quite a

lot to cover

so again i'm going to break it up into

two episodes

this will be part one let's go

[Music]

hi and welcome to episode 82 of

understanding dark table

to my mind the color calibration module

has

two personalities on one hand

it replaces the now deprecated

channel mixer module so that's one

personality and

its other personality is as a supplement

to the legacy white balance module

in this episode we're just going to look

at the first of those two personalities

using the new color calibration module

as

a channel mixer now before we start

i do just quickly want to revisit for

the benefit of those people who've come

straight to this video without watching

the

dark table 3.4 new features videos

in the preferences

and under processing we now have a new

entry auto apply chromatic adaptation

defaults now this pertains

to the color calibration module

specifically the default option here

is legacy so when you first install

dark table this will be set to legacy

and what that means

is that when you either import a new

image

or reset the history stack

on an image you've already got in your

library

the what legacy white balance module

will be

applied as per usual

and it will default to whatever was

the white balance set in camera at the

time of exposure

the color calibration module will not

be added to your list of active modules

that's the legacy mode if you change

this to modern what you are saying to

dark table

is whenever i import a new image or

whenever i

reset the history on an image i've

already got in my library

i want you to set

the legacy white balance module to

a new option which we'll look at in just

a sec called camera

reference and i want you to

activate the color calibration module

and we'll go into that a little bit more

in episode 83 but i did just want to

cover it for anyone who

didn't watch the new features videos

okay so

as you can tell i have it set to modern

so i'm using the color calibration

module by default for all of my

processing from this point forward

so to use the color calibration module

as

a channel mixer i have chosen this image

of desiree that i shot a few years ago

and what i've done is simply hit the

reset parameters button in the history

stack

and as you can see all of the regular

things get applied

color calibration is turned on and

because i've got

a scene referred workflow set in

preferences as well

it also means filmic and exposure uh

set to active as well so that

is the image straight out of camera

now if we look at the active modules

we will see that the white balance

module has had a little bit of a ui

refresh with dark table 3.4

we now have these four icons one for the

white balance as shot in camera

one for set the white balance detected

from an area and if we click on that we

will get the

white rectangle that takes up 99 of the

frame

and so dark table will do its best to

read the white balance

from the image itself we then have

a user modified section where you can

set your

own color temperature if you have a

specific reason for wanting to do that

and then we have this new one camera

reference

point in most cases it should be d65

now i will confess that d65 is a

whole new language to me i went and did

a bunch of reading

and i kind of understood some of it and

sort of eyes glazed over for a lot of it

however i did find an interesting

discussion on photo.net and i will put a

link to that

in the description down below so if you

really want to get into the weeds on

illuminance

then by all means hit that link and go

and read up

some interesting stuff in there and i

probably need to go and revisit it

but just understand that if you choose

modern

as the preference for chromatic

adaptation transform

in preferences then this

legacy white balance module will be set

to

camera reference or d65 and then

the color calibration module will do its

thing

now on this first tab the

chromatic adaptation transform if we

want to use

the color calibration module as a

channel mixer

we basically want to set the adaptation

to none and that is basically then

just turning off this tab

essentially it's removing all of the

options that are there with the

exception of the gamut compression

and so now what we've got is an r

channel a g channel and a b

channel and they are your old now

deprecated

channel mixer now i don't fully

understand the reasons for why the old

channel mixer was deprecated i think it

was something to

do with the the science and the color

space in which it worked i think

it assumed that you were working in an

srgb

color space all of the time and

obviously

these days that's not necessarily the

case

and the color calibration module will

work

in an unbounded color space uh

throughout its little part of the pixel

pipe

and that basically means you've got

more tones and colors and hues and

things to work with

that's my understanding don't shoot me

if i'm wrong

okay so how does this work well

basically each of these tabs

so r for red g for green b for blue

represents the output of that particular

color channel

and by default the input values

to each of those outputs is red is at

one and green and blue are at zero

on the green channel the green input is

at one

red and blue are at zero and on the blue

channel the blue channel

is inputting at one and red and green

are inputting at zero

so the idea is that you can now create

any mix

for the output of the red channel simply

by

choosing to re-adjust the sliders now

i am not going to pretend to know how to

use this in an efficient manner because

i never used the channel mixer either i

understand

the concept but i just i recognize that

it's way too powerful at all for my

limited understanding

and i would probably do more damage than

good

if i was to muck around with it if you

want to reset these you can just double

click on the sliders

that's nothing new and that will set

everything back to default values you'll

then notice there is a colorful tab

a brightness tab and a grey tab

now the colorfulness tab

is there to allow you to either

accentuate or attenuate

the intensity of anything you did

on the rg and b tabs so for example if i

was to come and do

something absolutely horrendous here i

have no idea what i'm doing but let's

just say i had done this

as a new mix for my red channel

i could go to the colorfulness tab and

this

input red slider will allow me to turn

down the effect of that red channel or

crank up

the effect of that red channel and then

the same applies for

whatever you do on the green channel you

would you would then have the ability to

attenuate

or accentuate that green

channel output on this green slider here

and then the same for the blue channel

you'll notice at the bottom here a

checkbox for normalized channels if you

activate that then regardless of

what you might dial in across these

three sliders

all of those values will be summed

together

and then divided back to a

value of one so essentially

even though you might have numbers that

don't necessarily add up to 1.0

whatever values you have you know

applied across these three sliders

will be correlated against each other so

that the output saturation

is consistent with the input saturation

it's just that the channel

mix will be a little bit different

next up we've got the brightness tab i

am just going to reset

these and the brightness tab as the name

suggests

simply allows us to alter the intensity

or the luminosity of each of our

red green and blue channels so we can

make our red channel darker

or brighter we can make our green

channel darker

whoa that's funky uh or brighter

or our blue channel darker oh

it's like morticia uh or brighter and

again the normalized channels checkbox

is there

to basically average out whatever

values you may have entered across these

three sliders

to then basically end up with a value of

one across those three values so that

the

output luminosity hasn't changed from

the input luminosity

but the luminosity of the individual

channels has been skewed

from where it was at the input stage

hopefully that makes sense

and then finally we've got the gray tab

and this is where you will do your

monochrome mixes of color images

now the moment you move any of these

sliders

away from their default positions at the

far left

your image will basically go black and

it is then a case of

deciding how much of each of the

three primary channels you want to

introduce into your monochrome mix

now sure you can just drag the sliders

around and find what looks good for you

or you can check out the new presets

that aurelian has created here

he did mention in his video that he was

not

entirely happy with the black and white

presets that existed

in the old channel mixer module and he

did confess that he made those up

many years ago when he knew less than he

knows now

and he doesn't feel today

in early 2021 that

those presets were as accurate

as they should have been and he believes

that these new

presets that he's come up with for the

color calibration module

are far more representative of

the film stocks that they are named

after so

if you did use the old channel mixer

module

for some of your past processing

exploits it might be worth going back

and particularly if you were working off

raw files

create duplicates disable the channel

mixer

enable the color calibration module and

maybe try some of these presets and just

see whether or not

you feel that these presets are a better

representation of the black and white

film stock they're trying to emulate

than the presets which were in the old

channel mixer module

now we'll just mention because the old

channel mixer module has been deprecated

it means that you won't

naturally find that module

available in the ui of dark table

anymore

however if you did watch the videos on

new features you would have seen me

cover the new

modules presets window

and within there there is a preset

of grouped modules for deprecated

modules

so even if you do want to keep using the

channel mixer module

you can access it from there if you want

to

but i think the recommendation is if you

want to do channel mixing

trickery today avoid the old channel

mixer module

and go with the new color calibration

module

alrighty i am going to leave it there

for this episode and in episode 83

we will look at using the color

calibration module

as a supplement to the legacy white

balance module

looking forward to it all right catch

you in the next one

[Music]

you