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What is a pinhole camera?

Cameras use apertures to control the amount of light entering the camera and reaching the image plane. Apertures allow only specific light rays from the scene to pass through, creating a clear image. Pinhole cameras exemplify this concept, using a tiny hole as the aperture to filter out unwanted light rays and form an inverted image on the image plane.

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Video transcript

- Hey. My name is Eben Ostby. I've been working at Pixar since we were just half a dozen people working on experimental short films. One thing that hasn't changed since then is the need for virtual cameras. And to understand virtual cameras, you need a firm grasp of how physical cameras work. And I love cameras. In fact, I collect and fix and sometimes even build them. I built this in a CAD system. And printed it out with 3D printing and it takes pictures. (camera clicks) Like that. And cameras come in all shapes and sizes, like this little, baby twin-lens. And this Classic American Argus. (camera clicks) So at Pixar, when we design a virtual camera our job is model what happens inside physical cameras. Have you ever thought about what a camera really does when we take a picture? (camera clicks) You probably know that a camera captures light on a piece of film or image sensor. But to understand how this works, let's build a very simple camera. We'll start with a box. This is our camera body. And a single piece of paper, which represents our image sensor or film. We'll call this the "image plane." You know what? Let's do this at a larger scale, like using an office as our box. Our scene is now outside the window. And our image plane is the opposite wall. We don't see a clear image. The problem is any point on our image plane is getting hit by light from everywhere in the scene. What we want is for each point on our image plane to be hit by light from a tiny region of the scene. Look at what happens if we cover up the window except for a little hole. We call this small hole the "aperture" of our camera. If you wait a few minutes for your eyes to adjust, voila. An image. The reason it works, is because the aperture only lets certain light rays through. At this point, here, on the image plane, only light rays from one direction can make it through the aperture. And those light rays come from light bouncing off this place in the scene. So the aperture is filtering out any light rays that don't come from the right direction. This simple camera design is known as a "pinhole camera." If we replace the back wall of the room with a great big sheet of photographic film, we could take a great picture that way. Did you know that the word camera comes from the Latin word for room? The first cameras were known as "camera obscura" meaning "darkened room." They were in fact, room-sized like our office. In the next exercise, you can use this pinhole simulator to take some virtual pictures. You can adjust the size of your pinhole, or aperture, and press here to capture an image. (camera clicks) While doing so, you'll have to answer some questions about what's going on. Such as, why is the image flipped? And more importantly, what happens if we change the size of our aperture? (camera snaps) See you in a moment.