Divide mode

- The next couple Hidden Gems will be devoted to seldom used blend modes that are very useful. In this Hidden Gem, I'm going to be talking about Divide Mode. This got slipped into a few versions ago and I bet a lot of people don't know what it's for. Well, it's very useful at one specific task: white balancing. Let's talk about how that works. A lot of people think of colors of having a value between zero and one. Zero is black, one is white. A truism about dividing is any number divided by itself equals one.

Two divided by two is one. A half divided by a half is one. Anything divided by the same thing equals one. And one equals white. So when we have a shot such as this, where the white balance is really off, I mean even these florescent lights have a blue tint, when we know they're suppose to be white. All we need to do is find that color that's supposed to be white and divide it out of the underlying image. To do that I'm going to select the Rectangle Shape Tool.

Make sure no layers are selected. So instead of masking it becomes shapes. I'm going to option all or click on stroke to change it to no stroke. I'm going to option or alt click on stroke to change it to no stroke. Option or alt click on Fill to change it to being a solid color. I could also just click on fill and say Solid. Okay, then I'm going to click on the fill color and use its Eye Dropper to pick something that's supposed to be white in this scene. I think this is white plastic, it's probably supposed to be white, but I know these lights are going to be the brightest thing in the scene and are probably burned out white.

So I'm going to click on that and that's the color I want to remove. Okay, now with no layer selected, double-clicking on the Rectangle Tool will create a rectangle shape that fills my composition, it uses that color I just selected. If I change its mode for the layer, not for the rectangle down shapes, but for the entire layer, to divide, you'll see it's pulled all of that blue out of the scene and now made things a nice, bright white.

If I think it's overdone it a little bit, it might be a little blown out, I'll press T for Opacity and back off the opacity of that layer blended on top. This is with no Divide at all, this is at full Divide, and this is with backing off to something that is not completely blown out, but still is a pretty good white. Now this obviously was an extreme case. Here's something more subtle on this woman on this phone. Even though she's smiling, she's laughing, she's having a great conversation, the light in this scene is a bit on the cool side.

It gives me a little bit of a, I don't know, distant feeling or foreboding, not necessarily warm and happy. But again, I bet that something behind here, like where this window is, is supposed to be pure white. So, no layer selected, Rectangle Tool, Fill, Color, Eye Dropper, what I want to be pure white in the final scene. Got it. Okay. Double-click Rectangle. There's my solid with the color I want to remove.

Change its mode to Divide, and now we have a brighter scene. Before. After. Now for my taste I think this could be an even warmer scene. Maybe this wall is supposed to be white instead of having that blue tint. That's fine, all I need to do is change the color of this shape layer. I'll turn it off for now, so it's not interfering with anything. Select it, Fill, Eye Dropper, choose the brightest part of the wall I can find, let's say, make that white, click OK, turn that layer back on.

Ah, now that's the sort of warmth I was expecting out of this scene. Now it looks like it's a little bit clipped and blown out through here, that's okay. I'll press T for Opacity and back it off a little bit. So I got a little bit of gradation still on her face, but it's a heck of a lot warmer than the original un-color corrected shot. Now, you can use color correction tools to perform this sort of operation and a lot of them do allow you to pick where the white point is in the scene. This is far easier in a program like say, Premiere. But in After Effects, particularly if you already have an edit set up of several layers, then you need to get that color bias out of all of them, sometimes that layer on top with a blend mode is your most expedient way to get the desired result.