Color calibration module reset calibration target area

content/module-reference/processing-modules/color-calibration.md

@@ -269,6 +269,8 @@ Note that the target value is not reset when you reset the module itself, but is
 
 The _take channel mixing into account_ option lets you choose where the target is sampled. If disabled, the target color is measured immediately after the _CAT_ (Chromatic Adaptation Transform) step, which takes place before any channel mixing. This means that if you have a calibrated profile in effect within the channel mixer, this profile will be discarded. If enabled, the target color is measured after the _CAT_ and the channel mixing steps, including any calibrated profile. This is the recommended option for most use cases.
 
+When selecting the area to measure chromaticity for color calibration in area mode, it is crucial to note that the selected area remains persistent as you edit subsequent images. To define the area, click on the eyedropper icon located to the right of the module. This icon displays the tooltip "set white balance to detected from area" on mouseover. Then, left-click and drag the mouse cursor over the desired region of the image to select the measurement area. This selection ensures consistency in your calibration workflow, as the same target area will be used for measuring chromaticity across multiple images, unless explicitly reset. To reset the selected area, simply right-click on the image. This feature allows you to maintain a consistent calibration reference, enhancing accuracy and efficiency during batch editing or sequential adjustments.
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 **Note**: If you are defining your target from a gray patch, you should know that the gray patch on color checkers is never entirely neutral. For example, Datacolor Spyder has a slightly warm gray (hue = 20°, chroma = 1.2) while X-Rite pre-2014 has a colder but more neutral gray (hue = 240°, chroma = 0.3) and X-Rite post-2014 is almost perfectly neutral (hue = 133°, chroma = 0.2). In general, it is not desirable to match the control sample against a perfectly neutral gray target, and it is actually wrong to do so when using gray cards and color checkers as a control sample.