Digital cameras are quite similar to traditional cameras in their operation. They both have a lens to focus the image, a shutter to allow light inside the camera, and an aperture to control the amount of light which enters the camera.

The differences between digital and traditional photography occur after the light enters the camera. A traditional camera captures the images on film, while a digital camera captures the image on an image sensor.

Image sensors are electronic devices made up of an array of electrodes (or photosites) which measure light intensity. The most common type of image sensor for digital cameras is the CCD (Charge-Coupled Device) although others such as CMOS and Foveon are sometimes used.

The number of photosites in the image sensor gives the digital camera its megapixel (millions of pixels) rating. Each photosite corresponds to a pixel in the final image, so a camera which is rated at six megapixels, for example, has an image sensor which is 3008 pixels wide by 2000 pixels high.

When light hits the image sensor it is converted into electrical signals which are amplified and fed to an analog-to-digital (A/D) converter. The A/D converter changes the electrical signal into binary numbers which are processed by a computer housed in the camera body. Once the numbers have been processed the resulting image is stored on a memory card.

Photosites can only measure intensity of light — not colour. In order to produce a colour image, each photosite must be covered with a coloured filter which can be red, blue, or green. These are the three primary colours which can be combined to produce any other colour including white.

The coloured filters are arranged in a grid so that there are twice as many green filters as there are red or blue. This is because the human eye is twice as sensitive to green light. Filters are arranged in a pattern called the Bayer pattern - one row of red, green, red, green (etc.), and the next row of blue, green, blue, green (etc).

Since each photosite can only be covered with one coloured filter, computer processing is necessary to produce a full coloured image. This is done by analyzing each individual pixel and its immediate neighbors and producing a composite colour from these calculations. For example, if a bright red pixel is surrounded by bright green and bright blue pixels, the bright red pixel must actually be white, because white is the combination of red, blue, and green. This process is called demosaicing.

After demosaicing the image is adjusted according to the settings on your camera. Most cameras have settings for brightness, contrast, and colour saturation. After these adjustments are made some cameras may also apply a sharpening algorithm to make the image clearer.

The final step before saving the image on the memory card is to compress it. Most cameras use JPEG as a compression format. This reduces the size of the file by eliminating excess data. This data cannot be recovered, so JPEG is called a ‘lossy’ format.

Many cameras have the ability to save uncompressed images as TIFF files or raw data. Raw data is the original photosite data even before demosaicing. It can be transferred to a computer for processing with special software that will perform all of the processing functions of the camera but with much greater control.

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There is a plethora of fine, solid quality compact digital cameras on the market today. And there are lots of camera models to choose from. So much so that it can be confusing for all but the most dedicated hobbyist. So which camera models are the cream of the crop? That depends a lot on what you intend to use the camera for, but we have listed a few models here that we think would make a fine purchase in most cases.

First of all, here are the features that we like to see in compact digital cameras. They are features that are most often appreciated by consumers in real world situations. Here is our list of required features:

* At least 3 megapixels
* Costs under $300
* Has at least a 3X optical zoom
* Can run on AA batteries
* Produces high quality, sharp photos

So with that criteria in mind, when you look over the compact digital camera field there are three models that meet or exceed these requirements and are often found on the top of most compact digital camera reviews by both consumer websites and consumers themselves. And here they are:

1. The Canon Powershot A510 is an incredible camera for the money. It comes in at the least expensive price point in our little group at $170. It’s a 3.2 megapixel camera which will do just fine for anything but the largest enlargements, and produces incredibly sharp and vivid photos. It sports a 4X optical zoom which provides a zoom range that is roughly equivalent to 35-140mm in 35mm. It also runs on AA batteries and can be expected to provide around 300 shots per set of batteries. And it has a movie mode w/sound which is a nice extra.

2. The Sony Cyber-shot DSC-W5 is a 5 megapixel camera that features an extra large LCD screen at 2.4 in. which can be very nice for those that can use a little more screen size. It’s optical zoom is adequate providing a 35mm focal length equivalent of 38-114mm. It also allows manual control of the exposure settings for those that like to go their own way. Another noteworthy mention is that this Sony manages power very efficiently and you can expect to get almost 400 shots before replacing the batteries in this unit. It costs $275.

3. The Kodak EasyShare Z700 is another fine compact digital camera with 4 megapixels that boasts an optical zoom of 5X which translates to an effective 35mm lens length of about 35-175mm. It also uses AA batteries and comes with it’s own charger, although it uses more power than the other two cameras listed here and can be expected to go through a set of batteries in around 200 shots. This Kodak model comes in around $240.

Any serious listing of compact digital camera reviews should include all three of these models and rate them highly overall. You choice should be based on what your individual needs and uses will be however, but all of them should provide years of solid, quality service.

Thad Pickering writes on many consumer related topics including audio and video. You can find out more about digital camera best buys and cannon digital cameras by visiting our Home Theater website.

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Shopping for a new digital camera can be quite frustrating with the hundreds of choices available. Digital camera reviews clarify this confusion by comparing camera features and options, then rating how each camera compares with similar models.

An effective comparison of best digital cameras requires two things: 1) the camera’s specs and features, and 2) performance ratings. Spec sheets and ratings are plentiful, but to efficiently compare digital cameras it’s important to set some guidelines.

Decide on how the camera will be used, the quality and size of final prints, and necessary features. Write these down and rank camera reviews and ratings against these standards. Whether looking for a professional or snapshot camera, scan the reviews and narrow your choices down to a few cameras before making final comparisons.

OK, Lets Cut to the Chase…

Re-visit the reviews for this short list and evaluate the digital camera ratings in more depth for the following criteria:

Design, Construction and Controls

Minor design differences can become significant in daily camera use. Carefully compare how each camera’s review is rated for design elements. Size and weight, body configuration, plus location of buttons, knobs and other controls can make a camera a joy to use or a real pain in the neck.

Evaluate how well the camera is put together. Are access doors for battery, memory, etc. solid and stable? What does the reviewer say about the shutter release, zoom and other buttons and knobs? How many photos will a fully charged battery take? Is the LCD bright and clear in both low light and sunny conditions?

The reviewer’s evaluation of the camera’s controls is critical. Can manual adjustments be made for different lighting conditions? How about auto-focus zones and exposure modes? Are controls simple and intuitive, or complicated menus?

Sensors, Pixels and Processors

These are the heart of a digital camera and determine photo quality, so closely compare how the reviewer rates them.

Generally larger sensors have more powerful and efficient photodiodes, and will produce higher quality photo images. Both CCD and CMOS sensor technology is advancing rapidly, but with each new development there are usually draw-backs, so compare carefully.

Digital camera marketing would have us believe it’s all about more megapixels. But it’s more complicated than that. Evaluate how each camera’s review rates pixel quality, not just quantity. Some cameras will actually take better pictures with fewer pixels.

What the camera’s processor does with the data collected from the sensor’s diodes is equally important. It must properly interpret color balance and interpolate pixels for sharp natural looking pictures. It must be able to do it quickly or you’ll have to wait too long between shots.

Lens Optics

In many ways lenses for digital cameras are simpler and less expensive than for conventional 35mm cameras. Even so, sensors and processors can’t produce a better photo than what’s visible through the lens. Compare the ratings because cheap lenses can distort images and colors.

In conclusion, decide on camera basics and budget range, scan enough reviews to pick a handful of finalists, then scrutinize the reviews and ratings on those cameras to find the perfect choice.

A list of top rated digital cameras can be found at our Digital Cameras Ratings page.

Digital cameras information from A to Z: camera types & features, how they work, accessories, photo printers, comparisons and more - plus digital photo processing tips and info at A-Z Digital Cameras.com, Your Complete A-Z Resource for Digital Cameras, Accessories and Information.

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