Composing light sources - Photoshop Tutorial

- [Instructor] I'd like to start with a small test scene, in which I'd like to demonstrate the basic principles of compositing. Put in a nutshell, compositing means to use different images and combine them to create a final image, or a final composite. So in Photoshop we're using layers in which we organize the different images and I have already created a few sets of layers that we will now work with here on the right side on the layers palette. So, let's just turn on the visibility of the layer group called Light. And indeed, it is a little bit as if I switched on a light switch. We now see that here's a little scene, and we have a sphere sitting on a ground, some background here, a horizon, and some blue ambient light. So this is effectively a light source that I have just switched on, and if we look into the layer group Light, we see that I have some more light sources prepared for this little scene, so let's just switch on another one. It's called Spot White, and that's what it is, it's a white spotlight coming straight from the top of the scene pointing down to our sphere. And this spotlight is now combined with the blue ambient light that I had on the layer Ambient. And this is noteworthy because what we see here is that the white spotlight is actually combined with the blue ambient light, it is not covering it up. And that's because I'm using a specific blend mode. So in Photoshop, every layer can have it's own specific blend mode, and by default this blend mode is Normal. And we see what happens if I switch the blend mode of the Spot White layer to Normal, now we can see that in the layer I had a black background and I painted the light information onto this black background, but when I keep this layer and the blend mode Normal, the black in this layer covers up everything below it. But, if I'm using the blend mode Screen, all the black in my layer has no effect on the layers below, only the light portions lighten up everything that is below, and so the information, the light information, in this layer is combined with the light information below it, rather than covering it up. And that is the most important principle of image compositing. You can combine different light sources and they will add up just as if there's now two light sources in the scene. They are on separate layers, but if you combine them with the right blend mode, it will look like an image that was created with two light sources. And the same is true of course for adding more light sources, so I have a red spotlight that's coming from the top right, and I even have a fourth light source, it's a green spotlight on the top left. And you can now switch on and off these different layers as you like, and you always end up with a combination of these different light sources, and with an end result that looks as if you used different light sources in it. So now, as we have our light sources neatly separated in their own respective layers, we can do even more. For example, if I turn on the red spotlight here, this layer has an opacity. It's currently set to 100%, so this light source is shining with 100% of its intensity into our scene. But if I lower the opacity on the layer, you will see that I can effectively decrease the intensity of the light source. So with the opacity setting of each layer, I effectively can increase or decrease the intensity of the different light sources, which gives me even more control of combining these light sources to a final result. It's really like having four lamps in my scene, and being able to dim every light source on it's own, and to create a final composite from that. And now another thing is possible, I will just increase the intensity of the red spotlight a little bit, now this light source here is red, that's clearly visible, but of course I can change the color of this light source. So let's just go into the adjustments, and let's use the Hue/Saturation adjustment. And now, by using the Hue slider, I can actually change the color of the light source that is now shining from the top right. And this gives us powerful control over the lighting of the scene. I will just keep it as a blue light source now. So this is what we have at our hands to combine different light sources. We can put every light source on it's respective layer, we turn the layer modes to screen, and then we can just combine as many light sources as we wish. We can adjust the intensity of the light by adjusting the opacity of the layer, and we can adjust the color of the light by using a adjustment on the color like a hue shift, or something like that.