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Life through a lens

PHOTOGRAPHY has been revolutionised by digital imaging. No longer is there an anxious wait while the film is processed. The time between shooting and seeing the image is quicker than even Dr Edwin Land, who invented the Polaroid system, imagined.

Civil engineering is one profession that will benefit from digital imaging. Engineers frequently rely on photographs to illustrate the general to the specific; from site records on a daily basis to detailing the alignment of a structural member. This is where digital images will be of enormous benefit to engineers.

The ability to e-mail images also makes it possible to consult with head office about the issue within minutes. A picture speaks a thousand words - concerns can be addressed immediately as engineers will have almost instant access to the image on their computer screens.

Digital cameras also give extra flexibility by allowing you to preview the image before recording.

Since engineers are not professional photographers this is a great advantage. And if you don't quite get it right on site software supplied with the cameras can help to clean up and enhance the image before transmitting or printing. These cameras will help you achieve the best possimodel tested here which is available with only 20Mb.

Memory cards are interchangeable. Once full, images can be downloaded on to a computer and used again. But as each high quality image uses approximately 1Mb of storage, 8Mb cards fill up very quickly. Just like extra rolls of film, extra cards are necessary to have on hand.

Batteries

Rechargeable batteries are a must as these cameras use up batteries very quickly.

Lenses

The image area of a digital camera is around 24mm x 16mm, smaller than that of a 35mm camera which is about 35mm x 24mm. The normal focal length is the diagonal of the format.

Thus for a normal lens on a 35mm format camera the focal length is (35 x 35) + (24 x 24) = 45mm, rounded up to 50mm for convention. This compares to a normal lens for a digital camera which is (24 x 24) + (16 x 16)= 28mm.

However, to avoid confusion, focal lengths and zoom ranges for digital cameras are quoted as they would be for 35mm film formats, as that is what everyone is used to.

All the cameras tested here had zoom lenses. The first number quoted here, the 'f' number, refers to the maximum aperture of the lens, also known as the speed of the lens. This is included for any slightly technical readers. The smaller the number, the faster the lens. Fast lenses are more light sensitive than slow lenses. An f2.8 lens is more light sensitive than an f4 lens and so will perform reasonably well in poor light conditions, such as on overcast grey days.

The second set of numbers quoted refers to the range of the ble image in any circumstance.

How they work

Digital cameras capture images on light sensitive memory chips called charged coupled devices (CCD) in the form of millions of tiny dots (pixels). This visual information is stored on electronic memory cards, usually in the form of JPEG files, the computer industry standard for storing still images. Once stored in the camera, images can be transferred to a Mac or PC for screen display, e-mailing or printing.

Picture resolution

Performance of digital cameras is measured according to the resolution of the CCD, expressed in megapixels (M) The higher the number of megapixels, the better the resolution of the picture.

Cameras quote the maximum number of megapixels available.

However, individual picture settings can be altered to produce either basic (low resolution - suitable for screen display or 3in x 2in print), good (mid range or 7in x 5in print) or high quality images (these are capable of producing a 10in x 8in print). For a good quality print you need to have at least 2M.

Memory

The number of pictures that your camera can save depends on the amount of memory available.

This is measured in Megabytes (Mb). Most cameras are supplied with an 8Mb card but larger cards up to 64Mb are also available. The exception is the Kodak zoom lens - typically 35-70mm is the standard. This means that any focal range between 35mm (wide for general shots) and 70mm (closer for portraits) is covered by this camera.

Focus range

The first set of figures quoted is the macro or close-up range of the camera - typically 1246cm. Clearly the smaller the first number, the better the macro facility. A camera with a close-up range of 12-46cm will focus on objects 12cm away from the lens, through to 46cm in the macro facility. That is why the Nikon is mentioned as having a good macro facility (focussing down to an incredible 7cm) The second group, typically 46cm8, denotes the focussing range when the camera is normal operating (non-macro) mode. All cameras focus to infinity.

Software

Most cameras are supplied with a bundle of software packages which allow you to download images from the camera and then manipulate or process pictures to suit your use.

There are many picture processing packages available.

Adobe Photoshop is an industry standard, but they are all adequate for the needs of the camera. Only with the Olympus will you have to buy additional software. However, as software applications are usually sold as a bundle with either a scanner or a printer, additional expense should not be necessary.

Weight

The size and bulk of the camera is important if you want to use it as a handy tool on site. But bear in mind that if you are in a harsh environment, look out for one that will withstand some rough handling.

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