How Software Manipulates Images on the Pixel Level

The humongous advantage of using numbers to represent images is that you can lighten an image, darken it, bring out contrast, sharpen it or blur it, turn it upside down, or transform it into a psychedelic abstract, all by using simple arithmetic. It's not so simple that we can sit at a computer with the Mona Lisa on the screen and subtract numbers from the color values in Mona's portrait, turning her smile into a frown. It would be an excruciating job, the kind of job computers are made for. A...

Diane Arbus

PUT a digital camera next to a camera that still uses film if you can find a new camera that still uses film. How are they different Some digital cameras are dead ringers for the 35mm SLR single-lens reflex that dominated photography for professionals as well as everyman for more than half a century. Nevertheless, a lot of the digital cameras are smaller than any film cameras you'll see outside of a spy movie. A few have some bizarre touches. One twists so that half the camera is at a right...

How the Digital Darkroom Works

CHAPTER 9 HOW SOFTWARE CHANGES PIXELS BY THE NUMBERS 142 CHAPTER 10 HOW DIGITAL RETOUCHING RESCUES FAMILY HEIRLOOMS 162 CHAPTER 11 HOW THE DIGITAL DARKROOM MAKES GOOD PHOTOS INTO GREAT FANTASIES 170 I have often thought that if photography were difficult in the true sense of the term meaning that the creation of a simple photograph would entail as much time and effort as the production of a good watercolor or etching there would be a vast improvement in total output. The sheer ease with which...

The Magnifying Glass Effect

Let's go back to that childhood fascination with magnifying glasses that set the scene for the previous illustration. Take a closer look at the hot spot of light created by the magnifying glass. You'll see that the spot is actually a picture, a small image of the sun. Now, remember how you moved the magnifying glass back and forth until it was just the right distance to start a flame You were focusing the picture the magnifier made on the leaf. In a camera, you have a lot of controls and...

Vari Angle Prism System

Supersonic Linear Actuator

In a lens using a vari-angle prism VAP to correct movements, such as some of Canon's video camera lenses and binoculars, gyrosensors are used to detect the slightest wiggle. The sensors send electronic information to a microprocessor built in to the lens. The microchip sends an electrical signal to voice coil motors, much smaller versions of the motors used to vibrate the cones in speakers. The motors sit at 90 angles to each other on the rim of the vari-prism. The VAP, which is positioned...

How Digital Cameras Create a Whiter Shade of White

Eyes do only half the work of seeing. They generate a lot of nerve impulses in response to stimulations from light striking the retina. But you ain't seen nothin' until the brain interprets the impulses. All the information that seems to come so naturally through the eyes shape, size, color, dimension, and distance is the result of the brain organizing sensory information according to a set of rules the brain starts compiling soon after birth. The truth of this is found in how we can play...

How Passive Autofocus Sees Sharp and Fuzzy

Passiv Autofokus Kontrast

Area of image used by skip ol photocells The camera's processor compares the intensity of the light falling on each photocell to the intensities of the adjacent cells. If the image is out of focus, adjacent pixels have similar intensities there is little contrast among them. The microprocessor moves the lens and again compares the photocell intensities As the scene comes more into focus, the contrast between adjacent photodiodes increases. When the microprocessor gauges that the difference in...

How Digital Lenses Manipulate Space

Telephoto and wide-angle lenses do more than change the size of your subject or the breadth of your image. They also change the relative sizes and relationships among individual objects in the photograph. A common misunderstanding is that lenses with different focal lengths change the perspective in photographs. For example, look at the three cubes shown here and guess which are representative of objects shot with a wide-angle, normal, or telephoto lens. WIDE ANGLE LENS NORMAL LENS TELEPHOTO...

How a Lens Focuses an Image

You must remember boring, sunny summer days in your childhood when you took a magnifying glass outside looking for anything flammable. Having spied a dry leaf, you held your magnifying glass between the leaf and the summer sun. Moving the magnifying glass back and forth with the precision of a diamond cutter, you found the exact point where the magnifier's lens concentrated the sunlight to form an image of the sun on the hapless leaf. Within seconds, the concentrated rays of the sun caused a...

How Active Autofocus Makes Pictures Sharp

Active Autofocus

Photographers can't always rely on automatic focusing because it's subject to the vagaries of any mechanism that cannot see but pretends it can. For the most part, autofocus has all but eliminated pictures of relatives with fuzzy faces and blurred birthday bashes, and it's a must for action shots and subjects who won't stand still for a portrait. The implementations of autofocus are as diverse as the minds of the ingenious engineers who invent them. We'll look here at two types of active...

The Workings of a Digital Camera

George Eastman, 1888, pitching the first Kodak camera AND there was, indeed, a time when it was just that simple. I recall my father's Kodak. I don't know what happened to it after he died, and so it took some research on eBay to find out that it was most likely a Pocket Kodak 1 or 1A, which Eastman Kodak began selling about the turn of the century the last century, like 1900. It was not a fancy camera. The upscale Kodaks had red leather billows, polished...