Digital cameras have certainly come a long way since their introduction only a few short years ago. Image quality has improved almost tenfold, while the latest enthusiast's models will truly give a semi-pro film single-lens reflex (SLR) camera a run for its money.
All but the cheapest digital cameras boast small colour screens for instantly reviewing pictures, removeable memory cards which can be erased and re-used indefinitely, video outputs for making instant slide shows on a TV set, while their native digital format eliminates the need for scanning when you want to electronically retouch or email pictures.
The quality of a digital camera is measured in megapixels, or millions of pixels. It refers to the total number of pixels on the light-sensitive chip which replaces film in a digital camera. The more pixels you have, the more detail captured, and the bigger the print you can make.
To calculate the megapixel resolution, simply multiply the horizontal and vertical number of pixels on the chip, adding several more for control and calibration use - hence 640 x 480 resolution equals 0.3 megapixel, 1152 x 864 equals 1.1 megapixel, 1600 x 1200 equals 2.1 megapixel, and 2048 x 1536 equals the current top of the range 3.3 megapixel.
Note that Fujifilm's proprietary Super CCD technology claims 4.3 megapixel resolution. It does this by taking a newly designed 2.4 megapixel chip and mathematically creating additional pixels to output a larger 4.3 megapixel file. In our resolving tests however, the Fujifilm Super CCD fell roughly between a 2.1 and 3.3 megapixel chip, revealing its 2.4 megapixel origins.
Since most colour inkjet printers like being fed around 200 pixels per printed inch, 1.1, 2.1 and 3.3 megapixel cameras will make good-looking prints up to 6x4in, 8x6in and 10x8in respectively.
All digital cameras employ JPEG compression to fit more pictures into their limited memory. While there are usually several levels of JPEG compression, most people use the best quality settings, typically producing files measuring around 800Kb for a 2.1 megapixel camera, or 1.3Mb for a 3.3 megapixel model. Since most 2.1 and 3.3 megapixel cameras come with 8 and 16Mb memory cards respectively, it's easy to figure out you'll only get about 10 best quality pictures on them.
Larger memory cards are very expensive, with 64MB costing up to pound;150 each. Sony's Mavica cameras offer an alternative by uniquely recording pictures on to cheap and readily available floppy discs, or even 8cm recordable CDs (156MB) on the latest MVC-CD1000 model. Unfortunately Mavica cameras are very large, and feature modest resolutions between 0.3 and 2.1 megapixel. Remember that with only 1.4MB on a floppy disc, you'll also not store many best quality pictures.
When it comes to comparinglenses, the optical zoom is the important figure, as digital zooms simply crop and enlarge the central portion of an image, reducing quality. If you're into making close-up pictures of very small objects, go for a model with a macro mode that can get closer than 10cm; those with only 20cm macros are not as effective for tiny subjects.
If you're into advanced photographic control, look for a model with aperture and shutter priority modes - although be aware that most digital cameras cannot expose for longer than eight seconds, and also many only have a couple of aperture settings to choose from.
Now for the bad news - digital cameras go through batteries at a rate of knots, often only giving a few days of modest use. Models which take standard "AA" size batteries may seem flexible, but alkalines drain particularly quickly, and rechargeables take about half a day to refresh - spare sets are cheap though. Models which take Lithium Ions can recharge in a couple of hours, and last longer too, but spares cost up to pound;40 - well it's swings and roundabouts I suppose.
Most modern digital cameras feature quick USB connections to your PC or Mac, transferring pictures in a matter of seconds. If you don't have USB on your PC, then you should consider a model with a slower serial interface, although these are increasingly rare. Alternatively, as stated before, the Sony Mavica range records pictures on to cheap standard floppy discs (or small recordable CDs).
Digital cameras are undeniably useful, and great fun too, but don't forget their downsides. With limited battery lives, you'd better not be more than a few days away from mains electricity, and you'll also need a nearby PC or notebook to copy images on to, thereby freeing up the expensive memory cards. Eliminating chemical processing is also a double-edged sword, as you're now responsible for the cost and effort of printing pictures.
This said, several models stand out as best buys. Canon's Digital Ixus remains the smallest model worth having with 2.1 megapixel resolution and a 2X zoom - it costs around pound;550. Sony's new DSC-P1 is a bit bigger, but boasts 3.3 megapixels and a 3X zoom, albeit costing pound;650. Also at pound;650 is the larger Sony DSC-S70, with 3.3 megapixels, 3X zoom, excellent control and long battery life.
True enthusiasts should dig deep and find pound;800 for either Canon's PowerShot G1 or Nikon's CoolPix 990 - both superb 3.3 megapixel models. At the budget end of things, Epson's PhotoPC 650 is remarkably good value at pound;225, although it's only 1.1 megapixel and has no optical zoom. Fans of floppy discs should check out the Sony Mavicas from pound;380 to pound;770, or the new CD1000 model, which may cost pound;1,000, but records loads of pictures on to 156Mb recordable CDs.
Gordon Laing is a freelance journalist and former editor of Personal Computer World magazine These cameras are available from all good high street electrical retailers and computer suppliers. Net retailers includewww.jungle.comwww.pcworld.co.uk