I can't see the images in the article but you have it right - the histogram is color values against frequency. You can then use the histogram to identify and h

I can't see the images in the article but you have it right - the histogram is color values against frequency. You can then use the histogram to identify and highlight particular color values in the image. This would identify the simple artefact described in the text. Link to Photoshop example use: http://www.ephotozine.com/article/using-the-histogram-in-adobe-photoshop-lightroom-4-21589 http://www.ephotozine.com/article/using-the-histogram-in-ado...