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--- doc:appunti:software:colorchecker_clones [2020/01/13 07:43] – [An Example Image] niccolo
+++ doc:appunti:software:colorchecker_clones [2020/01/27 12:18] – [The ColorChecker and its Clones] niccolo
@@ Line 1: / Line 1: @@
-====== The ColorChecker and its Clones ======
+====== The Grey White Balance Colour Card: an X-Rite clone ======
-{{.:color_management:colorchecker_gretag-macbeth.jpg?360 |https://commons.wikimedia.org/wiki/File:Gretag-Macbeth_ColorChecker.jpg}}
+**GWBCC** is a series of products manufactured by an **[[https://www.greywhitebalancecolourcard.co.uk/|UK company]]**; they are **[[wp>ColorChecker|color checkers]]** to be used in photographic color calibration. They have a certain notoriety for the fact that they cost half or a quarter of other much more famous products. In March 2019 I purchased for about 22 € the **2in1** model, a 140x88 mm plastic card which has the **24 color swatches** on one side and a **three grays** target on the other.
+Here I share my experience using that card to do **color calibration** of **photographies** and images acquired using a **scanner**. The workflow is entirely based on free and open source software: **Debian GNU/Linux** operating system, **The GIMP** as image processing software and **Darktable** for color calibration.
+The final word is: despite **the product lacks a real color calibration**, some results can be obtained at the cost of **a lot of preparatory work**, but without any claim of objective precision.
+===== The ColorChecker and its Clones =====
+[{{.:color_management:colorchecker_gretag-macbeth.jpg?360 |The original Gretag Macbeth ColorChecker. Photo from [[https://commons.wikimedia.org/wiki/File:Gretag-Macbeth_ColorChecker.jpg|wikimedia.org]]}}]
 The **[[wp>ColorChecker]]** is a registered trademark of a [[wp>Color chart|color chart]] introduced in 1976 and manufactured by **Macbeth**, now **X-Rite**; it features **24 squared patches** of various colors. The colors were choosen quite arbitrarly: six **shades of gray**, some **primary colors**  (red, green, blue, cyan, magenta, and yellow) and other colors of natural objects, like skin tones, foliage, etc.
 There are several manufacturers that sell **similar (cloned) color charts**; they are **more or less compatible** with the X-Rite original, where compatibility is measured on the precision obtainable using the same software procedures calibrated on the X-Rite product. The price and quality vary widely; durability of the materials, uniformity and consistency of the colors and printing method are the distinctive features.
-===== The Grey White Balance Colour Cards =====
+===== Solid Pigments vs Offset Printing and Dithering =====
-The most inexpensive color charts are obtained by **[[wp>Offset printing|offset printing]]**, the color patches are not made from solid color pigments, but obtained using **dithering** and **halftoning** of the primary printing colors. The following close-up are taken from the **The 2 in 1** checker, manufactured by **[[https://www.greywhitebalancecolourcard.co.uk/|Grey White Balance Colour Cards]]**; you can see how the patches are obtained with dithering, in particular the second photo shows the **grey patches** on the left: they are made by a **white background with black dots** over it:
+The most inexpensive color charts are obtained by **[[wp>Offset printing|offset printing]]**, the color patches are not made from solid color pigments, but obtained using **[[wp>Dither|dithering]]** and **[[wp>Halftone|halftoning]]** of the primary printing colors. The following close-up are taken from the **The 2 in 1** checker, manufactured by **[[https://www.greywhitebalancecolourcard.co.uk/|Grey White Balance Colour Cards]]**; you can see how the patches are obtained with dithering, in particular the second photo shows the **grey patches** on the left: they are made by a **white background with black dots** over it:
 {{.:color_management:colorchart-dithering-1.jpg?380|A color chart produced with offset printing}}