Written originally for Photography, a Stage 1 subject, during 2004.

Digital Photography

The idea of capturing an image has been around for centuries, people wanting to capture a moment to remember it forever. In ancient times people used camera obscuras to form images on walls in darkened rooms, image formation via a pinhole. In the 16th century the brightness and clarity of the camera obscura improved by enlarging the hole inserting a telescope lens. In 1727, Professor J. Schulze mixes chalk, nitric avid, and silver in a flask; notices darkening on side of flask exposed to sunlight. Accidental creation of the first photo-sensitive compound. In 1816 Nicephore Niepce combines the camera obscura with photosensitive paper, then ten years later he created the first permanent image.

Fast-forward to 1982, twenty-two years ago; Sony demonstrates the Mavica “still video” camera, and there, the digital camera is born. It seems that in the past 20 years, most of the major technological breakthroughs in consumer electronics have really based around the same idea. CD’s, DVD’s, High Definition Television, MP3’s are all built around the same basic process: converting conventional analog information (being represented by a gradually fluctuating wave) into digital information (represented by 1’s and 0’s, or digital bits). This shift in technology totally changed the way we handle visual information – and completely redefined what if possible.

The digital camera is one of the most remarkable instances of this shift because it is so truly different from its predecessor. Conventional cameras depend entirely on chemical and mechanical processes – all you need for digital cameras is a charged up battery, and away you go. The key difference between a digital camera and a film-based camera is that the digital camera has no film. Instead, it has a sensor that converts light into electrical charges. Most image sensor used by most digital cameras is a charge coupled device (CCD). The CCD is a collection of tiny light-sensitive diodes, which convert light into electrical charges. These diodes are called photosites. Put simply, each photosite is sensitive to light – the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate that area.

If you wanted to email a picture to a friend, you would need the image to be represented in the language that computer recognize and know – bits and bytes. Essentially, a digital image is just a long string of 1’s and 0’s that represent al the tiny coloured dots – or pixels – that collectively make up the image. The amount of detail that the camera can take in is known as the resolution, and it is measured by pixels. The more pixels, the more detail the photo will have. The more detail you have, the more you can enlarge the picture before it become out-of-focus or “grainy”. Some typical resolutions that you can find in digital cameras today are: 256x256 (Found on cheap cameras. The resolution is low, so low in fact that the picture quality is usually unacceptable. 65,000 total pixels), 640x480 (Ideal for emailing or posting on the internet. 307,000 total pixels), 1216x912 (If you’re planning to print the image, this is an ideal resolution. This is a “megapixel” image size – 1,109,000 total pixels), 1600x1200 (This is “high resolution”. Images taken with this resolution can be printed in larger sizes, such as 8x10 inches, with good results. This is almost 2 million total pixels). You can find digital cameras today with up to a 10.2 million pixel resolution.

In order to get a full colour image, most sensors use filtering to look at the light in its three primary colours. Once all three colours have been recorded, they can be added together to create the full spectrum of colours that you’ve grown accustomed to seeing on computer screens and colour printers.