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Digital and Optical Zoom

Most digital cameras allow you to zoom in or out. Be careful of cameras that do not have the word "optical" when describing the zoom range. In cheaper digital cameras there may be an attractive "digital" zoom range mentioned. Usually it will be about 3-to-1 or 4-to-1. With "digital" zooms, the image is magnified or cropped electronically and the image simply has larger pixels. You are not really zooming in on the subject. Instead, the subject is being electronically magnified, with image degradation as a result.

An optical zoom works by moving the lenses with tiny motors to change the focal length. Some of the best optical zooms can be as much as 10-to-1 (10x). Most medium priced digital cameras will have a zoom in the 6-to-1 or 3-to-1 range. Just be sure that you're buying an optical zoom. Most cameras now come with a combination of optical and digital zooms. That's okay, since the digital is usually not used until you have taken the optical zoom to its maximum.

LCD Screen

Most digital cameras have small lcd video monitors on the back of the camera, which will let you see instantly if the image should be kept or should be deleted. Virtually all digital cameras have an lcd screen on them - avoid ones that don't since the screen is very useful. This screen, at least for most cameras, will show what the photo you are about to take will look like. It also allows you to see all the images currently stored on the cameras memory card and to access whatever functions the camera may have.

Film cameras and digital cameras look the same, both have a lens system through which the light travels, but the similarity ends there. Not too many years ago, digital cameras with a 1.5 megapixel resolution and 30 picture storage cost an arm and a leg, and were the preserve of the professional or obsessive techie. Now, the quality of the cameras is so high and prices low enough that taking photos with a conventional camera and film is fast becoming a memory. One of the attractions of digital photography is the ease with which the images can be viewed, edited, enhanced or retouched and sent speeding across the internet at the touch of a button. Image editing software such as Photoshop or Paint Shop Pro allows you remove unsightly blemishes or "red eye" from your snaps, whiten your teeth (in picture form) or remove unsightly items such as power lines, telegraph poles or divorced or otherwise unwelcome relatives from your masterpieces.

CCD and Image Resolution

In a digital camera the light is focused on a digital sensor array Microchip, called a CCD (charge couple device), instead of a piece of film. This sensor has light sensing transistors, called pixels - short for "picture elements." The actual resolution of a camera is the total number of pixels that are located on the CCD sensor. When the image falls on the sensor, it triggers those phototransistors. Think of megapixels as millions of dots of light that are being stored for each picture. The more dots of light there are, the higher the resolution of the image. More pixel dots = bigger pictures. As a rule of thumb, the more megapixels the better. As newer and denser CCD chips are developed the megapixel rating of cameras will increase. This is a lot like the computer - not too long ago storage on your home computer was rated in megabytes. Right now the latest computers are rated in gigabytes, and it won't be long until we have terabyte computers, so expect the resolution and storage capacity of digital cameras to evolve at a similar rate.

Resolutions of digital cameras range from 0.3 megapixels to 5+ megapixels, (at present). A megapixel is just a way of expressing how many pixels are on the CCD sensor, in millions. Thus, a 2-megapixel camera has 2 million pixels on the cameras CCD sensor. They are laid out in an array with rows and columns and each pixel can be located in the grid by the combination of its horizontal and vertical position. For instance, take a camera which has an array of sensors in its CCD that is 3000 horizontally, and 2000 pixels vertically (3000x2000). If you do a simple mathematical formula on the pixel array size you will come up with the "Megapixel" rating of the camera. This is the number that most manufacturers use to sell the camera. The simple formula 3000x2000 = 6,00,000 shows that the camera has six million pixels, or is a "six megapixel" camera.

Storage Devices.
When the button is pressed, the image passes through the lenses and then goes through colour filters above each sensor. The sensor converts the image from light waves into an analog (varying) electrical signal. The analog signal is then input through an analog to digital converter (A-D Converter), where it becomes a pure digital signal. The image is then transferred into a temporary storage area inside the camera called "buffer memory," which is a chip or chips on the signal processing board. When the buffer is full, the image is written out to your storage media, such as a memory card.

A digital camera stores all of the pictures it takes on a memory card. The most common type of memory card is the compact flash card (CF Card). This is a little card about 1/2 the size, and a little thicker, than a credit card. Other memory types are Microdrives (MD) which are miniature hard drives, Smart Media, Secure Disk (SD), Memory Stick, or even a floppy disk (honest to God, I know someone who actually bought one). A memory card is measured by its memory size, in megabytes (MB). The more memory the card has, the more images it can hold. Thus, a 256 MB memory card will be able to hold many more images than a 32 MB memory card.

The common sizes are: 8, 16, 32, 64, 128, 256, and 512 megabyte. The really cheap cameras don`t provide an external storage card. They store the pictures in internal memory. Unfortunately, this memory usually won't hold many pictures, so you are very limited. How many images can be fitted onto a particular memory card varies greatly. The amount of images a memory card will hold depends on compression, resolution and photographic conditions.

Compression is how much the digital camera compresses an image. When a digital camera takes a picture, a very large file is created that holds the image. In fact, a picture produced from a 2-megapixel camera will produce a file size around 6MB - which is a very large file indeed. In order to fit more images on a memory card, digital cameras compress these image files. The amount of compression a digital camera does to an image can usually be set by the user. Standard compression modes on digital cameras usually include Normal, Fine or Superfine

Resolution is how many megapixels are on a CCD sensor in the digital camera. On most digital cameras, you can change the resolution. For example, a 2-megapixel camera can take images up to 1600x1200, which is a sizable image and one that creates a large file. If you do not want an image of this large size, you can change the resolution setting on the camera to make the image smaller (this will not effect the quality of the image, only its size). The smaller image size will have a smaller file size, allowing for more images to be placed on the memory card. For example, most 2-megapixel cameras can take pictures at the following resolutions: 1600x1200, 1024x768 and 640x480.

Photographic conditions. The type of picture you take can also play a small role in how many images can be stored on a memory card. Daylight pictures that are colourful tend to have a larger file size than images that are duller in colour or have been taken at night. The difference in file sizes is not huge, but photographic conditions do affect to a small degree how many images may be fitted onto a memory card.