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Digital Cameras

How Digital Cameras Work
A brief guide to the basics of Digital Cameras and links to further information...

Key feature

The key feature of the digital camera is that, unlike it's cousin the "real" camera, and all it's miriad ancestors, it has no film. It is this special difference that gives the digital camera all of its unique features. What replaces film is an image sensor comprising of a collection of tiny light sensitive diodes. These convert light into electrons (an electric charge). The brighter the light hitting an individual diodes the greater the charge. Next, the camera has to read the value of each diode. This is done using an analog-to-digital convertor.


But these diodes can only produce a black & white image since they only track the total intensity of the light. To get a colour image the light needs to be filtered to look at the three primary colours. This can be done in various ways. One being to use 3 separate sensors instead of one. The light that would have gone to just one diode is split and sent to three. Each sensor has an identical look at the image but their filters mean that they each only respond to one of the primary colours.


Having obtained the information on the colour and intensity of light the camera now needs to store the information, and be able to output the image to a computer for printing. Even for a camera with only 1,000,000 pixels this takes a lot of memory. Therefore some form of compression is needed.

One of the best methods is by taking advantage of repeating patterns. For example in a photo with a blue sky then there will be several areas with the same digital information. Represent this with a code number and then just use that the next time it appears. This is the same tecnique that is often used in text compression. For example the word 'elephant' can be replaced by the code 'e1' thus making the file size smaller.

Another compression technique is 'Irrelevancy'. This is far more tricky and involves throwiwg away data that is not easily detected by the human eye.

Storage and transfer to computer

Once you have taken a photo the picture is stored on some form of memory device. Most often it will be a 'flash memory' card. The picture is then transferred to the computer via a usb connecting lead or by a flash card reader.


Zoom: Tip - If you are looking for zoom then make sure it is optical zoom. An optical zoom changes the focal length of the lens. Digital zoom is a computer trick that can equally be done when the picture gets to your computer.


The amount of detail a camera can capture is called the resolution. It is measured in pixels. The more pixels, in general, the more detail to the photo. Here are some examples:-


There are 2 types used

1. CCD sensors - These have been around the longest. They generally have more pixels and work better in low light. However they are more expensive and use more power.

2. CMOS sensors - These have lower resolution but use less power.


Northlight Images
Headers: About, The Images, Ordering info, Viewing tips, Info & links, Copyright info.
Gallery of some great Black & White landscape digital photography. There are some great compositions here, and they really showcase the B&W format. You can buy the prints also online and there are also loads of articles and resources for digital photographers looking to improve their work - such as how to get the best black and white pictures. I'm going to take a new look at my digital camera and have a go myself!


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