Category Archives: The Digital Camera

The Digital Camera: The Spherical Lens (Part I)

We recently examined the way a spherical glass surface focusses light; however, this focussing property is not unique for light that travels from air into glass. Instead, this phenomenon occurs anytime light travels between two surroundings separated by a spherical boundary. For light that originates from a point source, the general equation that specifies the relationship […]

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The Digital Camera: Refraction by a Spherical Surface

Having learned about refraction in our recent posts, we can now begin to appreciate the imaging capability of a lens by applying the principle of Snell’s law to understand the way in which a glass surface can bend light rays to form an image. To see how this works, we first think about a cylindrical piece of […]

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The Digital Camera: The Pinhole Camera

Over a period of several months in 2005 and 2006, a half-dozen artists converted a shuttered F-18 aircraft hanger into the largest camera ever made. To darken the hanger the artists used 24,000 square feet of viscuine, 1,300 gallons of foam gap filler, one and a half miles of gorilla tape, and 40 cans of […]

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The Digital Camera: Total Internal Reflection

Snell’s Law enables us to predict the way a light ray will refract — or bend — when it enters a new surrounding with a different refractive index. If the new surrounding has a larger refractive index the ray will bend toward the surface normal; if the new surrounding has a smaller refractive index the ray […]

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The Digital Camera: Snell’s Law of Refraction

In about 140 AD the Greek scientist Claudius Ptolemy compared the direction light traveled in air with the direction it traveled after passing into water, and he recorded his observations in a table that looked something like this: Although Ptolemy presented his results as measurements, historians of science believe he used a mathematical rule to […]

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The Digital Camera: Where are we going and why?

I am writing The Digital Camera posts for this blog to explain the physical and technical principles that enable much of the magic in modern digital cameras. Although the field of optics is highly mathematical, I believe many of the important principles can be understood by using just a few basic notions from algebra and trigonometry. […]

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The Digital Camera: The Principle of Least Time

Imagine you need to move from your current location to a site that is 3 miles to the south and 4 miles to the east. As all crows and most people know, the shortest path between those two locations is a straight line. To determine the length of that straight line, though, we need to […]

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The Digital Camera: Reflection

According to Greek mythology, the goddess Nemesis tricked the handsome hunter Narcissus into falling in love with the beauty of his own reflection. Narcissus did not recognize that his reflection was simply an image, and so he gazed at his own likeness until he died. Carvaggio’s depiction of Narcissus’s fatal gaze at his own reflection. […]

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The Digital Camera: Shadows

In Mark Twain’s Connecticut Yankee in King Arthur’s Court, King Arthur would have burned Hank Morgan to death on a stake if light rays did not travel in straight lines. But when the moon blocked the sun’s rays from reaching Camelot, Hank was spared from the fire and, instead, christened the principal minister to the […]

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The Digital Camera: Light Rays

At around 300 BC the great Greek mathematician Euclid of Alexandria published what we now understand to be an outlandish theory about the geometry of vision. Euclid believed that the eye projected several tiny rays outward in the shape of a cone and used those rays to sense – or “see” – the objects in […]

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The Digital Camera: an Introduction

In the summer of 1826 Joseph Nicéphore Niépce pointed his camera toward the buildings and trees outside the window of his second-floor workroom in the French commune of Saint-Loup-de-Varennes. The camera was a simple device by modern standards: a single lens focused light onto a 20 x 25 cm pewter plate that was coated with […]

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