DIGITAL IMAGING
Conventional and digital photography are in many ways very similar, but in just as many ways, quite different. Both have their advantages, so in the foreseeable future, there will remain applications for each.
Conventional photography using chemically photo-sensitive film is a well known and highly developed quantity – very close to a perfected technology.
We know how to use it, how to get the best out of it, and how its life span can be optimised because it has been around for so long, used so much and had so much effort and expense spent on its development.
Digital photography is, on the other hand, a relatively new and radically different technique that records images in the form of digital (ie. 2 digit or binary) codes. In simple terms digital codes are similar to Morse code. A pulse of electricity indicates one number or digit, a second digit is indicated by no electrical pulse. By combining these pulses and lack of pulses into codes, we can, for example, create representations for letters of the alphabet; allowing us to write language or text on a computer. When we combine these electrical "pulses" and "no pulses" (or ‘ones’ and ‘zeros’) in more complex combinations, we can create more complex representations. These can include the colour, and degree of darkness or brightness in a single spot on a picture. When huge quantities of such dots are combined into a grid or array, we can then create a digital picture. (This is basically how digital photography works!) Each dot is referred to as a pixel ( PICTURE ELEMENT) and is represented by ‘bits’ of data – thus the digital image array is often referred to as a ‘bitmap’.
As time passes, digital photography is becoming better and better and its imagery now rivals that of traditional silver halide based photography. However, due to its nature, it is unclear at this point whether it will ever make traditional photography totally redundant, particularly in situations where extreme resolution or detail is required. Current levels of technology suggest digital will eventually become the technology we rely on for creating still images. However, in the shorter term silver image systems will actually be cheaper to use in many applications.
Photo chemical photography, based on the light sensitive silver compounds silver bromide, silver chloride and silver iodide ( known collectively as silver halides) has been with us since William Fox Talbot pioneered the negative/positive process in the first half of the nineteenth century. For most users this system has become synonymous with 35 mm photography.
Available equipment has achieved a very high level of sophistication whilst also producing very high quality images. The shutter and aperture exposure control system on film cameras, co-ordinated with a film speed (or sensitivity) system based on a simple geometric progression (the ISO system), allow the photographer to select combinations of film speed, shutter speed and aperture to creatively increase or decrease depth of field, enhance or reduce movement and operate in virtually any lighting conditions. The disadvantages of 'old style' photography lie principally in the areas of the requirement for elaborate facilities to process the image, the delays processing entails and the long-term storage of finished images. The Polaroid process provides an integrated shooting and processing medium but is expensive and limited in its applications. Advances in archival processing have improved storage options for photo-chemical imagery but it is still easily damaged by such everyday hazards as dust and moisture. Making a print from a negative involves copying one analogue system to another similar system and physical problems, such as those previously mentioned, causing constant difficulties.
Digital photography largely avoids these pitfalls. Storage media for digital image files (generally magnetic or optical in nature eg. diskettes, CD ROM or hard disk) have long been shown to be reasonably resistant to physical problems and to often still be readable and/or repairable after damage that would render a film negative useless. For example, scratches on CDs can generally be repaired. A scratch on an original film negative usually means disaster.
Apart from this, a digital code stays a code until it is interpreted into an analogue artefact by the use of hardware and software. Consequently, digital can be copied to digital directly. Reading the code is largely unaffected by physical factors which trouble analogue copying and this opens the way for simple, cheap archiving of digital imagery. Digital storage systems can even be arranged so that if data is lost through damage or equipment failure, the missing code can be reconstructed by analysis and comparison of the remaining pieces of data. In essence this means that the digital image you create today can be preserved with no loss or deterioration into the foreseeable future by simply copying the file to new media. With the exception of some very simple and relatively cheap cameras, many of the early problems of digital have been eliminated or have become largely irrelevant.
For example, all but the most basic digital cameras now have image sensors capable of giving high enough resolution for good quality postcard-size prints at very least. When you take a digital photo the image is captured by a sensor (more on these in Lesson 2), which is actually an analogue device. The digitising process and writing of the image data to memory take time. This means that many digital cameras cannot shoot a rapid sequence of photos - you have to wait 10 or more seconds between shots. For most people this presents no more problem than waiting for the flash unit to recycle on a conventional camera if you were, for example, shooting in dim light. However for the professional, where 'motor-drive' shots are an expectation of their shooting hardware , high end digital cameras now employ fast memory buffers and new sensors to allow sequences of five or more images to be fired-off at a time. Increases in the speed with which an image can be scanned from the sensor and processed, have helped eliminate this problem. These facilities come at a price and digital cameras are still more expensive than their conventional counterparts. As time progresses, this price gap is diminishing.
Significantly, digital cameras are based on conventional cameras for their exposure systems and allow, depending on the degree of sophistication, the same image controls as any standard film camera. The film speed, shutter and aperture systems of ‘old style’ cameras are an integral part of all but the simplest point-and-shoot digital hardware. The range of digital cameras now covers the same sort of scope as that of 35 millimetre cameras. Consequently choosing a camera tailored to suit your needs is easier, even if the number available may seem daunting.
Digital cameras store images on compact ‘cards’, which are essentially computer memory chips.
The most common way to store images from a digital camera long-term is to 'download' them from the camera’s memory card (the digital ‘film’) onto a computer hard drive. This then allows the camera memory card to be re-used over and over again. High quality images use a lot of memory space and can run anywhere from 1 megabyte compressed files to the 8 megabytes of space or more for uncompressed files (see Lesson 3 – File formats, for more info). This sounds a lot, particularly when a large word processor document (say 30 to 60 pages) is only in the 100 to 200 kilobyte range. However, this means that lower quality images (or smaller sized images) usually are in a similar file size range to that of the large word processor file. This means even the lowly (and ageing) floppy disc can store 2 to 4 smaller images or 1 compressed high-quality image. Beyond this, very few computers produced in the past few years do not have a CD rewritable/recordable drive or cannot be fitted with one for a reasonable sum. Even with uncompressed images of 8 megabytes you can store 85 shots, on one CD/R disk. That's economical in anyone's language.
The only other worry people sometimes express about digital images is the future compatibility and accessibility of today's file formats for long-term storage. The nature of digital imagery means all current digital image formats are based on the concept of the bitmap mentioned earlier. Consequently programmes like Adobe Photoshop or JASC Paint Shop Pro will perform conversions of one format to another. Given this feature of digital photography it seems likely that we will be looking at today's images, albeit copied digitally (but without loss of quality) to new formats, long into the next generations.
Digital photography is computer friendly and inexpensive, once you have the equipment. You can take any number of photos, place them onto a computer, and manipulate the images to use them in different ways, change effects and even send the image via the internet quickly to any part of the world.
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