Digital Cameras

Digital cameras give a whole new meaning to the idea of painting by numbers. Unlike old-style film Cameras, they capture and record images of the world around as using digital technology. In other words, they store photographs not as patterns of darkness and light but as long strings of numbers. This has many advantages: it gives us instant photographs, allows us to edit our pictures, and makes it easier for us to share photographs using cell phones (mobile phones), e-mail, and web sites.

How Ordinary Film Cameras Work

If you have an old-style camera, you'll know that it's useless without one vital piece of equipment : A Film is a long spool of flexible plastic coated with special chemicals (based on compounds of silver) that are sensitive to light. to stop light spoiling the film, it is wrapped up inside a tough, light-proof plastic cylinder- the thing you put in your camera.

When you want to take a photograph with a film camera, you have to press a button. This operates a mechanism called the shutter, which makes a hole (the aperture) open briefly at the front of the camera, allowing light to enter through the lens (a thick piece of glass or plastic mounted on the front). The light causes reactions to take place in the chemicals on the film, thus storing the picture in front of you.

This isn't quite the end of the process, however. when the  film is full, you have to take it to a drugstore (chemist's) to have it developed. Usually, this involves placing the film into a huge automated developing machine. The machine opens up the film container, pulls out the film, and dips it in various other chemicals to make your photos appear. This process turns the film into a series of "negative" pictures-ghostly reverse versions of what you actually saw. In a negative, it uses them to make prints (finished versions) of your photos.

If you want to take only one or two photographs, all of this can be a bit of a nuisance. Most people have found themselves wasting photographs simply to "finish off the film." Often, you have to wait several days for your film to be developed and your prints (the finished photographs) returned to you. it's no wonder that wonder that digital photography has became very popular-because it solves all these problems at a stroke.

(Incidentally, if you want to learn more about film cameras and traditional photography, see our main article on how film cameras work.)

How digital Cameras Work

Digital cameras look very much like ordinary film cameras but they work in a completely different way. When you press the button to take a photography with a digital camera, an aperture opens at the front of the camera and light streams in through the lens. so far, it's just the same as a film camera. From this point on, however, everything is different. There is no film in a digital camera. Instead, there is a piece of electronic equipment that captures the incoming light rays and turns them into electrical signals. This light detector is one of two types, either a charge-coupled device (CCD) or a CMOS image sensor.

If you've ever looked at a television screen close up, you will have noticed that the pictures is made up of tiny colored dots or squares called pixels. Laptop LCD computer screens also make up their images using pixels, although they are often much too small to see. In a television or computer screen, electronic equipment switches all these colored pixels on and off very quickly. Light from the screen travels out to your eyes and your brain is fooled into see a large, moving picture.

In a digital camera,exactly the opposite happens. Light from the thing you are photographing zooms into the camera lens. This incoming "picture" hits the image sensor chip, which breaks it up into millions of pixels. The sensor measures the color and brightness of each pixel and stores it as a number. Your digital photography is effectively an enormously long string of numbers describing the exact details of each pixel it contains. You can read more about how an image sensor produces a digital picture in our article on webcams.

How digital Cameras use digital technology

Once a picture is stored in numeric form, you do all kinds of things with it. Plug your digital camera into your computer, and you can download the images you've taken and load them into programs like photoshop to edit them or jazz them up. Or you can upload them onto website, email them to friends, and so on. This is possible because your photographs are stored in digital format and all kinds of other digital gadgets-everything from MP3-playing iPods to cellphones and computers to photo printers-use digital technology too. Digital is a Kind of language that all electronic gadgets "speak"today.

If you open up a digital photograph in a paint (image editing) program, you can change it in all kinds of ways. A program like this works by adjusting the numbers that represent each pixel of the image. so, if you click on a control that makes the image 20 percent brighter, the program goes through all the numbers for each pixel in turn and increases them by 20 percent. If you mirror an image (flip it horizontally), the program reverses the sequence of the numbers it stores so they run in the opposite direction. What you see on the screen is the image changing as you edit or manipulate it. But what you  don't see is the paint program changing all the numbers in the background.

Some of these image-editing techniques are built into more sophisticated digital cameras. You might have a camera that has a optical zoom and a digital zoom. An optical zoom means that the lens moves in and out to make the incoming image bigger or smaller when it hits the CCD. A digital zoom means that the camera blows up the incoming  image without actually moving the lens. so, just like moving closer ti a TV set, the image degrades in quality. In short, optical zooms make images bigger and just as clear, but digital zooms make bigger and more blurred.

Why Digital Cameras Compress images

Imagine for a moment that you're a CCD or CMOS image sensing chip. Look out of a window and try to figure out how you would store details of the view you can see. First, you'd have to divide the image into a grid of squares. So you'd need to draw an imaginary grid on top of the window. Next, you'd have to measure the color and brightness of each pixel in the grid. Finally, you'd have to write all these measurements down as numbers. If you measured the color and brightness for six million pixels and wrote both down both things as numbers, you'd end up with a string of millions of numbers—just to store one photograph! This is why high-quality digital images often make enormous files on your computer. Each one can be several megabytes (millions of characters) in size.

To get around this, digital cameras, computers, and other digital gadgets use a technique called compression. Compression is a mathematical trick that involves squeezing digital photos so they can be stored with fewer numbers and less memory. One popular form of compression is called JPG (pronounced J-PEG, which stands for Joint Photographic Experts Group, after the scientists and mathematicians who thought up the idea). JPG is known as a "lossy" compression because, when photographs are squeezed this way, some information is lost and can never be restored. High-resolution JPGs use lots of memory space and look very clear; low resolution JPGs use much less space and look more blurred. You can find out more about compression in our article on MP3 players.

Most digital cameras have settings that let you take pictures at higher or lower resolutions. If you select high-resolution, the camera can store fewer images on its memory card—but they are much better quality. Opt for low-resolution and you will get more images, but the quality won't be as good. Low-resolution images are stored with greater compression.

Inside a digital Camera

Ever wondered what's a digital camera? What takes the photo? where's it stored? what makes the flash work? And how do all these bits connect together? when you take electronic gadget apart, they're much harder to understand than ordinary machines (things that work through a clear physical mechanism): you can't always see which part does which job or how. Even so,it can be quite illuminating to peer into your favorite gadgets to see what's hiding inside. I don't recommend you try this at home: opening things up is the quickest way to invalidate your warranty; it's also a good way to ensure they'll never work again.

The main Parts of a digital Camera

Photo: The parts in a basic digital camera. Were it not for the LCD screen and batteries (the two biggest components), you could probably make a camera like this as small as a postage stamp

I've opened up the camera in our top photo—and these are the parts I've found inside:

1. Battery compartment: This camera takes two 1.5-volt batteries, so it runs on a total voltage of 3 volts (3 V).
2. Flash capacitor: The capacitor charges up for several seconds to store enough energy to fire the flash.
3. Flash lamp: Operated by the capacitor. It takes a fair bit of energy to fire a xenon flash like this, which is why a lot of indoor flash photography quickly uses up your batteries.
4. LED: A small red LED (light-emitting diode) indicates when the self-timer is operating, so you can take photos of yourself more easily.
5. Lens: The lens catches light from the object you're photographing and focuses it on the CCD. 
6. Focusing mechanism: This camera has a simple switch-operated focus that toggles the lens between two positions for taking either close-ups or distant shots.
7. Image sensor: This is the light-detecting microchip in a digital camera and it uses either CCD or CMOS technology. You can't actually see the chip in this photo, because it's directly underneath the lens. But you can see what it looks like in our article on webcams.
8. connector: Attach a USB cable here and connect it to your computer to download the photos you've taken. To your computer, your camera looks like just another memory device (like a hard drive).
9. SD (secure digital) card slot: You can slide a flash memory card in here for storing more photos. The camera has a very small internal memory that will store photos too.
10. Processor chip: The camera's main digital "brain". This controls all the camera's functions. It's an example of an integrated circuit.
11. Wrist connector: The strap that keeps the camera securely tied to your wrist attaches here.
12. Top case: Simply screws on top of the bottom case shown here.

Another important part, not shown here, is the LCD display that shows you the photos you've taken. It's mounted on the back of the electronic circuit board so you can't see it in this photo.

Writer: Mr. Krishan Kumar Saini

Today We have Learnt about Digital camera. Hope this lesson is helpful for you.