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Course: Pixar in a Box > Unit 6
Lesson 1: How virtual cameras workCamera lenses
Now we'll add a lens to our camera and explore the idea of an f-stop. Pinhole cameras use lenses to focus light and create sharp images. The lens curvature affects the focal point, and the focal length determines the field of view. Aperture size controls light exposure, measured in F Stops. Wide angle, long, and 50mm lenses offer different perspectives.
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- The eyeball has a lens, aperture (pupil), and image plane (retina). Does it act like a camera as well?
edit: And why does our vision blur sometimes as we age? Is it because our eye changes shape?(72 votes)- That is absolutely correct. That is also why pupils in our eyes gets wider in dark rooms and gets really narrow when walking outside on a sunny day.(41 votes)
- At, what camera is that? 3:21(5 votes)
- That's an Olympus OM-4T, which is a 35mm film (SLR) camera. This one was probably made in the 1990's.(11 votes)
- Is a camera with a long lenses better than a camera with a short lenses?(6 votes)
- Short answer: no. Longer answer: As the Introduction to Cameras video showed (trying to take a selfie with a long lens), you need to choose the lens that best suits your purpose. If you're trying to capture something at a distance without losing the context of the subject, you'll probably want a longer lens. If you're trying to capture something nearby and you are trying to make sure the entire subject is included, you may want a shorter lens.(7 votes)
- The eyeball has a lens, aperture (pupil), and image plane (retina). Does it act like a camera as well?
edit: And why does our vision blur sometimes as we age? Is it because our eye changes shape?
Great Question
That is absolutely correct. That is also why pupils in our eyes gets wider in dark rooms and gets really narrow when walking outside on a sunny day.At, what camera is that?In pinhole camera, you have mentioned that the target rays are scattering in all directions. If the aperture is small, the rays will go straight and form an upside down image. However, now for camera lens the rays are represented as coming parallel. So how is this possible? Are these (Pinhole camera and camera lenses) different models? If not how can we combine them? Many thanks for your time! 3:21(5 votes) - It is the short film by Pixar named the blue umbrella(4 votes)
- In pinhole camera, you have mentioned that the target rays are scattering in all directions. If the aperture is small, the rays will go straight and form an upside down image. However, now for camera lens the rays are represented as coming parallel. So how is this possible? Are these (Pinhole camera and camera lenses) different models? If not how can we combine them? Many thanks for your time!(3 votes)
- He says that the light is very close to parallel because it is coming from very far away- the sun. The sun is about 150 million kilometers away, and the light it emits is randomly scattered like in the previous examples. However, since it is so far away, the light that reaches us seems parallel because the scattered portion has scattered many millions of kilometers from us.(3 votes)
- I don’t understand why a camera with a larger mm focal length results in an image with a large object because the light focuses farther away from the aperture... It doesn’t really make sense.... Can someone please explain?
Seeand onwards 1:57(2 votes)- I think the best way of thinking about it is to go back to the idea of a pinhole camera. When your pinhole is a longer way from the image plane, the resulting image is large. In the pinhole camera lesson you can see the geometry that makes this so. With a lens instead of a pinhole, you're simply adding the ability to focus to this geometric arrangement.(2 votes)
- how are glasses and cameras different?(3 votes)
- cameras are more sensitive to light than the human eyes .cameras have the "flash" setting which creates light . humans eyes adjust in time even when waering glasses. human eyes adjust over time and can filter light better . if you were to take a picture while the sun was directly behind you the background maybe so bright that you can bearly see what the picture was . human eyes adjust to the light and the dark on there own to help you see better in the dark and when your in a bright place your eyes will help to make it not as bright by filtering the light .it may still seem very bright but your eyes are working to fix that . cameras have to move there lens to foucus . on the other hand while a human is wearing glasses the lens dont move they stay in place and your brain works with the lens to make the image clear .(0 votes)
- at the timethey said curvature, what is that 1:21(2 votes)
- i dont understand any of this(2 votes)
Video transcript
- Earlier, we found that to make a very bright image
with our pinhole camera, we had to use a large aperture. But when we did this, our resulting image was blurry because light rays from each point in our scene spread out into a larger area on our image plane. Here's an example. The light rays are
coming in from the right and they're just about parallel, like they're coming from
an object like the sun that's really far away. With a tiny aperture, just one tiny point on the image plane would be illuminated by these rays. But to make a bigger aperture work, we need to aim all of these light rays onto a tiny point without
discarding any of them. We want to bend them. And what do we use when
we want to bend light? A lens. If we add a lens to our camera, it will cause our light
rays to converge like this. The point where these
parallel light rays converge is known as the Focal Point. It turns out that the shape
or curvature of the lens determines how sharply
the light rays are bent. If we increase the curvature of our lens, the rays focus very close to the lens. And if we decrease the curvature, they focus farther away. What we want is to focus the light rays exactly on our image plane. That will give us a sharp image. And for any particular distance between lens and image plane, there's a lens design, or curvature, that will focus the light rays on the image plane. We call the distance at which the lens focuses these parallel rays the Focal Length of the lens. You can have a lens that focuses close to the aperture and you'll get a wide field of view. We call that a Wide Angle Lens. For example, a 28 millimeter lens, like the one we're using here, has a focal length of 28 millimeters and produces an image
with a wide field of view. Or you can have a lens that focuses light further away from the aperture. We call this a Long Lens. For example, a 120 millimeter lens, like the one we're using here, has a focal length of 120 millimeters. So we'll capture less
of the scene, like this. While a 50 millimeter lens, like the one we've switched to here, gives us this natural-looking perspective. For any given lens, the
film or light sensor needs a certain amount of light to record an image properly. Too little, and it just sees darkness, Too much, and it just sees white. We control how much light it receives by adjusting the size, or diameter, of the aperture, which we also measure in millimeters. Some cameras, like this one, allow you to set the
aperture using this ring. But the numbers on the ring aren't measured in millimeters. The numbers here are called F Stops and is defined to be the ratio of the focal length of the lens to the diameter of the aperture. So if we want a 25 millimeter aperture on a 50 millimeter lens, we'll set the F Stop to two because 50 millimeters divided by 25 millimeters equals two. F Stops are handy because they tell us exactly how much light gets through, no matter the focal length of the lens. For example, if we set the F Stop on a 100 millimeter lens to two, we get the same amount of light as we do with a 50 millimeter lens with the F Stop set to two. The F Stop is there for an important idea. Let's stop here so you can get some practice with it
in the next exercise. And just to make it clear, I did take that with an F Stop of two.