# ICC profiles in Debian

## Suggested default profiles

For a conservative color-managed workflow,
use only ICCv2 profiles, and target an offset print press.
Enable color-mangement in Scribus, GIMP and related applications,
and configure them to use the following profiles by default:

  * RGB photos: sRGB v2 profile *without* black point compensation
    * E.g. "sRGB2014"
  * RGB spot colors: sRGB v2 profile *without* black point compensation
  * CMYK photos: Generic CMYK profile
  * CMYK spot colors: Generic CMYK profile
  * CMYK printer: ISOcoated_v2_bas.ICC (FOGRA39L based)

This setup is commonly used even in some more modern workflows
targeting digital printers,
where the printer then internally translate to their different profile.


## Color calibration

Some applications can optionally simulate the target color space
on your computer screen.
This is called soft-proofing.

Simplest (but also least optimal) way to enable soft-proofing
is to set your monitor to sRGB
(or just set all knobs in as default position as possible)
and configure your applications to use the following profile:

  * RGB monitor: local unique profile or sRGB v2 monitor profile

Or better, measure the physical performance of your monitor
and generate a local profile uniquely describing that,
e.g. using package displaycal and a supported colorimeter.
Then configure your applications to use that profile for soft-proofing:

  * RGB monitor: Your local unique profile


## Black point compensation and ICCv4 profiles

Black Point Compensation (BPC) is a technique
commonly used in color-managed workflows based on ICC profiles.
Originally introduced precomputed in ICC profiles,
nowadays (with faster computers and support for software-based on-the-fly BPC computing)
it is recommended to compensate only late in the workflow,
in the color management processing software -
not hardcoded in the ICC profiles tagged onto the media.

ICC profiles are commonly available in two flavors -
v2 often using lookup tables, and v4 more often using algorithms.
V4 profiles may lead to better results than v2,
but assumes that BPC is done in software.
Therefore, to avoid compensating twice (both in profiles and software)
either use v4 profiles only in a pure v4 workflow,
or mix v4 only with non-BPC v2 profiles.
Hence above suggestion to use non-BPC v2 profiles by default
which should work with both (modern) v2 workflows and v4 workflows.

Notably, it is recommended to *NOT* use the ICC v2 profile
named "sRGB Color Space Profile.icm" (sRGB IEC 61966-2.1),
as it contains BPC and is constructed in a way that is internally inconsistent,
leading to incorrect results in some workflows.

For more detailed and authoritative explanations,
see <https://www.color.org/WP40-Black_Point_Compensation_2010-07-27.pdf>
and <https://www.color.org/ICC_White_Paper_26_Using_the_V4_sRGB_ICC_profile.pdf>.


## Quality check

To compare the Free ICC profiles against commercial counterparts,
see "Quality of Default ICC Profiles"
at <http://www.oyranos.org/2011/11/quality-of-default-icc-profiles/>.

You might also find this article, comparing 15 sRGB profiles, relevant:
<https://ninedegreesbelow.com/photography/srgb-profile-comparison.html>.


 -- Jonas Smedegaard <dr@jones.dk>  Thu, 09 Feb 2023 03:59:51 +0100