IntroductionIf quality images suitable for Web use is what you want from your digital camera, then a good 1-megapixel model will suffice. However, if you wish to use your camera in conjunction with a photo-quality printer to create A4-size images striking enough to hang above the fireplace, then the camera you need should be in the 3-megapixel bracket. (Megapixel means a million pixels. The more pixels an image has, the larger it can be at high quality.) There exists a bewildering range of cameras, offering a profusion of diverse technologies and resolutions – making it difficult for novices to navigate both the cameras’ specifications and the performance claims of manufacturers. Here, we strive to strip matters down to the key issues and features. Technologies
One camera on test – the Canon EOS D30 – employs a new way to capture images. The D30 uses a CMOS chip (Complimentary Metal Oxide Semiconductor) rather than a CCD (Charge Couple Device). On the plus side, CMOS offers low power-useage, yet high-level signal-processing capabilities – thanks to the size of the chip. Unlike tiny CCDs, the CMOS chip in the EOS D30 is a chunky 23-x-15.5mm. This means pixels are bigger, so better at collecting light. The more light collected, the better images will be. Also, because the area collecting data is bigger, the image can be focussed on a larger area. This means that CMOS-based models can use SLR lenses; you can interchange lenses designed for the Canon range of film cameras with the EOS-D30. CCD models, though, rely on specially made lenses to focus light on the tiny CCD. But the downside with CMOS is expense. The process creates image noise, so the manufacturer has to ensure this noise doesn’t affect final image quality – passing the expense of this onto consumers. But CCD technology also offers advantages. Its small form-factor means the technology allows for smaller cameras and higher resolutions. Resolution
The most-quoted digital-camera specification is resolution but, while being a good measure of practical image print-size, high resolution doesn’t guarantee high quality. It is, however, likely that an image taken on a high-resolution model will be sharper than that captured on a low resolution one – because the former offers more available points of information. A resolution of 300dpi is usually quoted as being the minimum for professional publishing, so this is the figure we’ll take for optimum output on inkjets. This means that, at 300dpi, a 3.2-megapixel camera would print an image at 174-x-131mm (6.8-x-5.12-inches). However, because inkjet printers are adept at maintaining quality at resolutions as low as 150dpi, it’s likely you can blow-up images from 3-megapixel models to A4 size with scant deterioration in image integrity. There’s also a difference between the stated resolution of image-capturing chips and the number of pixels actually used by the camera. This is because pixels around the edges of the chip serve no useful purpose. Of course, this doesn’t stop camera manufacturers from quoting chip resolution rather than maximum output-resolution. Hence models like the Dimage 7 “has” a 5.2 megapixel resolution, but in fact is a 4.95-megapixel model. This is the equivalent of a 21-inch monitor having a 20-inch viewable image. In the specifications quoted in this feature, we state both actual and claimed resolutions, allowing you to compare them. Storage
The cameras on test are all high-resolution models, and, as such, require hefty storage solutions. There are three main types of storage for digital cameras: CompactFlash, Smart Media and Memory Stick (MS). MS is exclusive to Sony; while CompactFlash is the most widely used of the formats, and offers the most flexibility. There are two types of CompactFlash cards: One and Two. Type One cards are more common. However, type Two cards – such as the IBM MicroDrive – have capacities of up to 1GB. Because storage cards add to the price of cameras, manufacturers tend to skimp on them. The largest bundled card is a measly 16MB. Fortunately, card prices are coming down, so it’s worth investing in extra capacity. Expect to pay around £1 per MB. Size
Camera bulk can be a key purchasing-factor for amateurs, most of whom prefer their cameras to be pocket-sized. Just like heavy laptops, weighty cameras tend to get left in drawers. If you’re likely to get most use out of a compact, lightweight model, then buy one. Video
Most of the cameras on test can capture short-span video clips. This is a consumer feature that looks good. But, in truth, its usefulness and practicality is limited. If you want digital video, buy a digital camcorder.