Last week I wrote about the basic techniques used in compositing. When you are trying to combine very different elements into a brand new creative image it requires more techniques and even some preplanning. As humans, our optical systems are pretty amazing. Over millennia, we have evolved the ability to detect when something is just not right in a scene. We might not recognize just what it is, but we know when something is off.
The most critical and immediate thing we notice is where the shadows don’t make sense. Shadows are a natural consequence of the blocking of light. Our brains see where the light sources are and then know where the corresponding shadows should be. What is usually the biggest light source? The sun, of course. Now for the tricky question; how many suns do we have? That’s right, only one. Why then do so many composite fails look like they were shot on Tatooine? Yep, people put images together with competing suns.
Here are two images that I want to put together. The model was from last year’s Photoshop World Westcott Lighting both, while the other is a river in New Mexico. As you can see her lighting came from high up on the right side. Unfortunately, the lighting for the river scene comes from the opposite direction. If you just put them together and mask out her black background, it doesn't look natural.
Luckily, since we are not trying to be photojournalists you have options to correct this. The easiest thing to do is just flip one of the images on its axis. Since there is no text in either image it doesn’t matter which one. I flipped the background and…voila!
More for next week!