doc:appunti:software:colorchecker_clones
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doc:appunti:software:colorchecker_clones [2020/01/12 06:36] – [Create the CIE file with color values of the GWBCC Colour Card] niccolo | doc:appunti:software:colorchecker_clones [2020/01/27 12:20] (current) – [Solid Pigments vs Offset Printing and Dithering] niccolo | ||
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- | ====== The ColorChecker and its Clones | + | ====== The Grey White Balance Colour Card: an X-Rite clone ====== |
- | {{.: | + | **GWBCC** is a series of products manufactured by an **[[https:// |
+ | |||
+ | 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**, | ||
+ | |||
+ | ===== The ColorChecker and its Clones ===== | ||
+ | |||
+ | [{{.: | ||
The **[[wp> | The **[[wp> | ||
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. | 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> | + | The most inexpensive color charts are obtained by **[[wp> |
- | {{.: | + | [{{.: |
- | {{.: | + | [{{.: |
====== Color calibration using Darktable ====== | ====== Color calibration using Darktable ====== | ||
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In the figures above you can see how the histogram looks like when choosing the wrong or the right color profile. An photo with **shadows and highlights equally distributed**, | In the figures above you can see how the histogram looks like when choosing the wrong or the right color profile. An photo with **shadows and highlights equally distributed**, | ||
- | Return to the **lighttable mode** and choose **export selected** from the right menu, choose **PFM (float)** format and **Lab** profile. The exported file will be saved into a **darktable_exported** subdirectory. | + | Return to the **lighttable mode** and choose **export selected** from the right menu, choose **PFM (float)** format and **Lab** profile. The exported file will be saved into a **darktable_exported** subdirectory. It is not required to add the //output color profile// module to the image history, just export with the options stated above. |
===== Create a CHT file for the GWBCC Colour Card ===== | ===== Create a CHT file for the GWBCC Colour Card ===== | ||
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- Return into **lighttable mode**, into the **styles** section **create a new style** which will contain the history of the selected image. This is the only one that you will apply to all the other images. | - Return into **lighttable mode**, into the **styles** section **create a new style** which will contain the history of the selected image. This is the only one that you will apply to all the other images. | ||
+ | The style created by '' | ||
+ | |||
+ | <code xml> | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | </ | ||
+ | </ | ||
===== An Example Image ===== | ===== An Example Image ===== | ||
Here it is an example of what I obtained with the above workflow. The first image is what actually was acquired from the scanner. No particular color space was associated to the image, so if we open the image **assuming the sRGB** color space we get a very dark image (the **histogram** is unbalanced toward the dark tones): | Here it is an example of what I obtained with the above workflow. The first image is what actually was acquired from the scanner. No particular color space was associated to the image, so if we open the image **assuming the sRGB** color space we get a very dark image (the **histogram** is unbalanced toward the dark tones): | ||
- | {{.: | + | {{.: |
+ | |||
+ | **Raw image from the scanner. If no specific color space is declared, sRGB is assumed | ||
Applying the **linear Rec2020 RGB** color space (just declaring it, without actually changing the pixel data), we get a better image; even the histogram is more balanced between dark and light tones: | Applying the **linear Rec2020 RGB** color space (just declaring it, without actually changing the pixel data), we get a better image; even the histogram is more balanced between dark and light tones: | ||
- | {{.: | + | {{.: |
+ | |||
+ | **Using Darktable, the Linear Rec2020 RGB color space is applied.** | ||
The final image is just the //raw// one with the **style applied**. A quite good result considering that no manual adjustment was made! | The final image is just the //raw// one with the **style applied**. A quite good result considering that no manual adjustment was made! | ||
- | {{.: | + | {{.: |
+ | **The image after applying the Darktable style.** | ||
====== Creating a picture of a color chart ====== | ====== Creating a picture of a color chart ====== | ||
doc/appunti/software/colorchecker_clones.1578807401.txt.gz · Last modified: 2020/01/12 06:36 by niccolo