From the course: SynthEyes Essential Training (2015)

Camera basics - SynthEyes Tutorial

From the course: SynthEyes Essential Training (2015)

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Camera basics

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- It's important in 3D tracking to have a basic understanding of how a camera works. We're just going to brush the surface here, but for a more in-depth understanding, check out 'Foundations of Photography' by Ben Long here on lynda.com. Basically, the image is taken and the light comes through the lens, through the shutter, and onto the sensor. Now, the important thing that we need to know for 3D tracking, is the size of that sensor and the lens. These two work together. So, if you don't know one or the other, it's probably not going to help you a lot in 3D tracking. For example, if you had a Canon 7D, the lens might be a 35mm lens, but there's a crop factor on the sensor for the Canon 7D, so it's actually going to be the equivalent of a 55mm lens. And so, if you don't know that sensor size, that can change things pretty drastically. Let's take a look at an example of that. So here in SynthEyes, I've tracked the exact same shot and used the exact same points. I've even locked these points right to the corner of this box. So it should line up perfectly. Now this shot has the exact camera information plugged in, it has the right sensor size, and the right focal length. And as you can see, the shape of the box pretty much matches right on. But now, let's see what happens when we move to a camera that does not have the right information. So we go up to the top here and switch over to camera01. You can see the shift. Now, that's supposed to be lining up because these are the same locations, but because the focal length is different, it's changing everything. And you can see the difference in the spread of the points. If we look here, the blue Xs represent the proper 3D space while the green Xs represent the wrong focal length. Now if you don't have that information, which happens often, you still can get a decent solve. But, I just want to illustrate the fact that if you do not have both pieces of information, you're going to be guessing. And you can see what will happen when you don't have the right focal length. It can change the distance of points and objects in your scene. So, having an understanding of how the camera works will help you when trying to figure out your match move.

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