Many people have asked me how to edit gemstone as it is one of the difficult job as the colour of the gemstone in the photo and the colour of the gemstone in real would be completely different. This is because we have different lighting and settings when the picture was taken. So to correct the colours there are 2 quick adjustments you can do to the image other than Brightness/Contrast.
They are Levels and Curves. These are better than Brightness/Contrast because brightness contrast will not bring out the black colour in the image and rather increase the lightness. This is a key difference as the colour of the image change. After using Curves and Levels if the gemstone is still too brightly colours you can use the Image > Adjustment > Hue/Saturation method and correct the saturation which is the second horizontal scroll to get the perfect colour of your gemstone.
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