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### Course: Pixar in a Box>Unit 6

Lesson 1: How virtual cameras work

# Depth of field

In this video we'll explore why regions in our scenes can go "out of focus." Lenses focus light rays for sharp images. When objects are close, light rays aren't parallel, causing out-of-focus images called circles of confusion. Depth of field is the in-focus area, controlled by lens choice and aperture. Small aperture (large f Stop) creates deep depth of field, while large aperture (small f Stop) creates shallow depth of field.

## Want to join the conversation?

• At what movie is the girl from?
• that is Riley from Inside out
the emotions Joy ,Anger , Sadness,Fear,Disgust.and bing bong (bing bong is not an emotion) are inside Riley's head
• What is the meaning of focus at infinity? I observed that when focus slider is set to INFINITY, pizza is blurred. How this can be explained mathematically?
• Focus at infinity means that objects infinitely far away will be in focus. In other words, light that's parallel will be focused. That's why objects close up, such as the pizza will not be in focus.
• Why cant we have focus from far places
• is it just me or is joy a control freak?

I mean in the movie, she only allows happy memories
• At what causes the rays to fan out?
Is it because we are focusing on one part of the whole image?
If the whole scene is in focus, will all the rays be parallel?
What do they mean hitting the lens at an angle?
• how do I become an animater
• What was it again? I...just don't understand really much.🙀
(1 vote)
• How can you use depth of field?
(1 vote)
• witch video has the text for the effects lesson
(1 vote)
• Can somebody help me... I thought that the "Aperture" and the "F-stops " where the same thing. Moreover I thought the bigger the aperture the bigger the depth of field would be. But doing the "Practice" questions seems like it is the opposite... Im confused..
(1 vote)
• "Aperture" and "F-stop" are the same concept. But "F-stop" is a special way of describing the aperture size by comparing it to the focal length of the lens. It's really "the focal length of the lens divided by the aperture size". So - do your division - the smaller the aperture, the larger the f-stop number will be.
(1 vote)

## Video transcript

- In the previous video, we saw how lenses can focus parallel light rays to a point on our image plane, resulting in a sharp image. This means that if our image plane is set at the focal length of our lens, then objects that are very far away appear sharp. For example, imagine a scene with Joy standing a mile away from the camera, like this. If we look at the scene from the side, we get this. Notice the light rays that bounce off Joy and enter the camera are approximately parallel. If we place our image plane at the focal length of the lens, Joy will be in focus. But what happens when we try and make an image of nearby objects in our scene? Imagine we move the camera so that Joy is standing just a few feet away. Now pick any point on Joy and look at the light rays that are heading from that point toward the lens of our camera. Notice that these light rays aren't parallel, they fan out. Because they're hitting the lens at an angle, they are redirected to a point a little farther away behind the image plane. Over here. And where the light rays actually hit the image plane, they're spread out in larger circles instead of tiny points. This results in an image of Joy which is out of focus. To see this effect clearly, check out this out of focus shot of lights. These blurry circles are known as Circles of Confusion. They're a result of light rays which haven't been focused to a point on the image plane. And when an image is in focus, the circles of confusion are so small, they appear as points in our image. We can bring Joy into focus by moving the image plane back a little. There. At this distance, Joy will be in sharp focus. Remember with our pinhole camera just the size of the pinhole determined how blurry or sharp everything in our image was. And with a tiny pinhole, the entire scene was in focus. But now, with a lens in there, only a slice of our scene will be in focus. And anything which moves outside of this in-focus region, either too close or too far away, will appear out of focus. This is known as Depth of Field. Filmmakers control the depth of field with their choice of lens and aperture, or F Stop. Let's do an example with multiple Joys at different distances from our camera. If our aperture is very small, that would be with a large F Stop, then the depth of field will be larger and the transition from sharp to blurry is very gradual. To see this, let's start with a subject that's in sharp focus. As I move it farther away, the blurry region doesn't change very much. This is Deep Depth of Field. So more than one of our Joys will be in focus. Now, let's increase the size of our aperture, that is, a smaller F Stop, and start again with our subject in focus. Moving the subject even just a little further away causes the blurry region to get big fast. This is called Shallow Depth of Field. Now, just a tiny slice of our scene will be in focus. So with a small aperture, or large F Stop, the depth of field is deep. The entire scene is in focus. With a larger aperture, or smaller F Stop, the depth of field is shallow. Only a small slice of our scene is in focus. In the next exercise, you'll have the opportunity to explore how both aperture and lens length affect depth of field.