Digital Cameras
A camera is a tool used to capture an image which can then be printed, viewed, duplicated and distributed.

Sources for camera reviews -
www.dpreview.com
www.imaging-resource.com

Digital Photography:
The first digital camera dates back to 1975. The first commercially available cameras from 1995, but they were very expensive and of little practical use in the production of quality photographic images. By 2000 they started replacing film in everyday use. Today they are comparatively cheap and capable of exceeding film in the quality of the image they create, and faster and more flexible in use. Digital image capture has replaced film in almost all sectors of the photographic industry. Less than 0.01% of images captured today are recorded on film.

 
Advantages of Digital Photography:
In traditional or 'legacy' photography the film is exposed in the camera and then has to processed and printed. This means that it has to be taken to a photographic lab. To be economical the film has to be finished before it is processed which may mean taking 36 pictures. The photographer can not be sure that they have captured the images the way they wanted.
In digital photography an individual image can be taken, checked, re-shot if required. This is a huge advantage for the photographer. It is possible to carry out the complete process on your own computer and printer, avoiding the need to use a lab. You also save on the cost of buying film. For professional photographers it is an advantage to have a digital original image as previously images from film required scanning before they could be used in publication.

Other advantages of digital photography are in the colour technology available in cameras. Colour photography on film is dependent on the light source. Most film is designed for use in daylight and filters have to be used under artificial light. Digital cameras can be controlled to work under most of the common artificial light sources without need for further correction.

Technical specifications of Cameras

The design of digital cameras originally followed that of their film counterparts.
The majority were similar in design and use to film based compact cameras. 'Compact' cameras having a viewfinder. usually situated above the lens which takes the picture or increasingly commonly having no viewfinder - expecting you to use the screen on the back of the camera to compose your picture.

A Digital S.L.R is very similar to a film S.L.R where the film is replaced by a digital sensor.
Digital cameras incorporate a screen on the back of the camera which is used to view the images taken. This screen is also used to access the camera settings to adjust and customise the camera. As digital camera technology has developed so the number of controls and options available have increased.

The most recent addition to the range of cameras available are the so called mirrorless cameras.
Essentially this technology replaces the optical viewfinder in a D.S.L.R. with an electronic viewfinder.
There are advantages and disadvantages to this type of camera.
Advantages include the ability to move the lens closer to the capture sensor, potentially increasing image quality. The viewfinder can also show you the exposure in the viewfinder taking into account the shutter speed and aperture set, a D.S.L.R. camera does not do this. Using an electronic viewfinder also makes the cameras easier to use for video recording.
Disadvantages include power consumption, as using an electronic viewfinder will drain the camera battery much quicker.
Some photographers might also prefer the more traditional optical viewfinder over a digital representation in an electronic viewfinder.

Over time, the image capture size has increased, from 3,4,5,6 megapixels to 10, then 12 and more commonly now to 24, 36 megapixels and beyond.
The pixel count is about the maximum printable image size and not directly related to quality. So a 10 inch by 8 inch print only requires around 6 or 7 megapixels, depending on the printing equipment used is is possible to create a high quality print to this size from a 4 megapixel camera. Shooting with a 24 megapixel camera will allow you to print up to 30 inches by 20 inches if that is what you need to do.

The pace of development is still high, last year Canon introduced more than a dozen new cameras. The average production run of a compact digital camera lasts about 1 year, and digital S.L.R. cameras about 2 - 3 years.



Technical information on sensor sizes
 
The quality of images obtained from digital cameras is determined by a number of factors including: chip size, number of pixels and quality of the lens used

Without manipulation, the size of prints from cameras is approx:
1 megapixel 4"x 3".
2 megapixel 5.5" x 4"
3 megapixel 6.5" x 5"
4 megapixel 7.5" x 5.5"
6 megapixel 10" x 6.7"
8 megapixel 11" x 8"
10 megapixel 13" x 8.5"
12 megapixel 14.2" x 9.5"
15 megapixel 15.8" x 10.5"
21 megapixel 18.5" x 12.5"
24 megapixel 20" x 13.3"
36 megapixel 24.5" x 16.4"

Images can usually be interpolated to twice the size without noticeable loss of quality.
e.g. 4 megapixel from 7.5"x 5.5" to 11"x 7.5"
6 megapixel from 10" x 6.7" to 15" x 10"
24 megapixel from 20" x 13.3" to 30" x 20"

    

Increasing image size beyond this requires careful manipulation and some loss of quality should be expected.
Printing using 'rip' software can double the size of the print.