This is how Photoshop’s “Divide” blend mode works and how to use it to remove colour casts
Photoshop has a whole bunch of different blend modes but knowing what they all do… Well, even many of the most advanced Photoshop users don’t know what they all do. That not knowing could be holding you back, though. And this video is a perfect example as to why.
I’ve been using Photoshop since about Version 3.0 (yes, I’m that old), but I don’t recall ever once using the “Divide” blending mode. After watching this video from Unmesh at PiXimperfect, though, I wish I’d started looking into it years ago. Unmesh starts by showing how it works in a practical sense, and then explains the underlying maths behind it to help you understand how it does what it does.
The maths behind how Photoshop’s layer blending modes work can sometimes feel a little… I was going to say intimidating, but they can also feel kind of useless. Like, why does it really matter? Well, once you understand the maths behind them, you have some idea of exactly what they’ll do to your image.
In the video, Unmesh shows how we can remove colour casts by simply creating a colour layer of the same colour as the cast, and then use the divide blending mode to remove it from the underlying image. But he explains which parts of the image and its layers equate to which parts of the equation, which really opens up the potential of this blending mode can do.
It’s not just good for removing colour casts, but without understanding how it can remove them, how will you ever figure out what else it can do? Maybe I should start using it more.
John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.