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Pixar in a Box
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.
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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)
At3:21, what camera is that?(5 votes)- That's an Olympus OM-4T, which is a 35mm film (SLR) camera. This one was probably made in the 1990's.(12 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.(8 votes)
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It is the short film by Pixar named the blue umbrella(5 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)
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.At3:21, 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!(4 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?
See1:57and onwards(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)
When the lens focuses close to the aperture, why do we get a wide field of view?(2 votes)- It's due to the geometry of the image plane relative to the aperture. A lens has much in common with a pinhole, so you can figure out the geometry of the resulting image by assuming that all the light has to pass through one point in the middle of the lens. Draw yourself a diagram like you saw in the pinhole camera lesson.(1 vote)
- The American Revolutionary War (April 19, 1775 – September 3, 1783), also known as the Revolutionary War or American War of Independence, was the military conflict of the American Revolution in which American Patriot forces under George Washington's command defeated the British, establishing and securing the independence of the United States. Fighting began on April 19, 1775 at the Battles of Lexington and Concord. The war was formalized and intensified following passage of the Lee Resolution, which asserted that the Thirteen Colonies were "free and independent states", and the Second Continental Congress in Philadelphia ratified the Declaration of Independence on July 4, 1776.
In the war, American patriot forces were supported by the Kingdom of France and the Kingdom of Spain. The British, in turn, were supported by Hessian soldiers from Germany, some American Indians, Loyalists, and freedmen. The conflict was fought in America, the Caribbean, and the Atlantic Ocean.
The American colonies were established by Royal charter in the 17th and 18th centuries. They were largely autonomous in domestic affairs and commercially prosperous, trading with Britain, its Caribbean colonies, and other European powers via their Caribbean entrepôts. The British gained victory over the French in the Seven Years' War in 1763, and tensions and disputes arose between Britain and the Thirteen Colonies over policies related to trade, trans-Appalachian settlement, and taxation, including the Stamp and Townshend Acts. Colonial opposition led to the Boston Massacre in 1770, which strengthened American Patriots' desire for independence from Britain. The earlier taxation measures were repealed, but the British Parliament adopted the Tea Act in 1773, a measure which led to the Boston Tea Party on December 16. In response, Parliament imposed the Intolerable Acts in mid-1774, closed Boston Harbor, and revoked Massachusetts' charter, which placed the colony under the British monarchy's direct governance.
These measures stirred unrest throughout the colonies, 12 of which sent delegates to Philadelphia in early September 1774 to organize a protest as the First Continental Congress. The Congress drafted a Petition to the King asking for peace, and threatened a boycott of British goods known as the Continental Association if the Intolerable Acts were not withdrawn. Fighting began in March at the Battle of Lexington on April 19, 1775. In June, the Second Continental Congress formalized Patriot militias into the Continental Army and appointed George Washington commander-in-chief. The coercion policy advocated by the North ministry was opposed by a faction within Parliament, but both sides saw conflict as inevitable. Congress sent the Olive Branch Petition to George III in July 1775, but the King rejected it. Parliament declared the colonies to be in a state of rebellion in August.
Washington's forces drove the British army out of Boston during the Siege of Boston in March 1776, and British commander in chief William Howe launched the New York and New Jersey campaign. Howe captured New York City in November, and Washington responded by secretly crossing the Delaware River and winning small but significant victories at Trenton and Princeton, which restored Patriot confidence. In summer 1777, Howe succeeded in taking Philadelphia, forcing the Continental Congress to flee Philadelphia.
In October, a separate British force under John Burgoyne was forced to surrender at Saratoga. This victory was crucial in convincing France and Spain that an independent United States was a viable entity. With Philadelphia occupied, Washington and 12,000 Continental Army troops secured refuge in Valley Forge from December 1777 to June 1778. At Valley Forge, General von Steuben drilled the Continental Army into a more viable fighting unit, but as many as 2,000 Continental Army troops died from disease and possibly malnutrition over a brutal winter.
France provided the Continental Army with informal economic and military support from the beginning of the war. After Saratoga, the two countries signed a commercial agreement and a Treaty of Alliance in February 1778. Spain also allied with France against Britain in the Treaty of Aranjuez in 1779, though it did not formally ally with the Americans. Nevertheless, access to ports in Spanish Louisiana allowed the Patriots to import arms and supplies, while the Spanish Gulf Coast campaign deprived the Royal Navy of key bases in the south.
This undermined the 1778 strategy devised by Howe's replacement Henry Clinton which took the war into the Southern United States. Despite some initial success, Cornwallis was besieged by a Franco-American force in Yorktown in September and October 1781. He attempted to resupply the garrison but failed; Cornwallis surrendered in October. The British wars with France and Spain continued for another two years, but Britain's forces in America were largely confined to several harbors and Great Lakes forts, and fighting largely ceased in America. In April 1782, the North ministry was replaced by a new British government which accepted American independence and began negotiating the Treaty of Paris which was ratified on September 3, 1783. Britain acknowledged the sovereignty and independence of the United States of America, and the American Revolutionary War came to an end. The Treaties of Versailles resolved Britain's conflicts with France and Spain.[42](2 votes)
3:21Video 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.