Some blend modes in Photoshop are crucial to most any genre and are probably used daily by the majority of photographers, while others are much more specialized and rarely used. This great video examines one of the lesser used modes and shows how it can be employed to create powerful color grades.
Coming to you from Blake Rudis over at f64 Academy, this great tutorial examines the Difference blend mode in Photoshop. First of all, how does the Difference blend mode work? Well, it's exactly that, a difference. It looks at the channel information for each pixel, then subtracts the smaller channel value from the bigger one (it wouldn't make sense to have negative luminance values). For example, if the top layer has a pixel of (166, 72, 224) and the bottom layer's corresponding pixel is (188, 23, 240), the resultant pixel will be (22, 49, 16). So, why is this so useful? It turns out that this behavior creates pleasant color grades with relative ease because of how it interacts with areas of varying luminosity. It's also highly useful for manually aligning layers. It can be a bit tricky to intuitively predict how it will treat colors at first, though, so check out the video above for more!