MAYBE YOU HAVE YET TO BUY A DIGITAL CAMERA. Perhaps you have one, but have yet to take it diving. Or possibly you have already taken underwater digital pictures but been disappointed by the results. Its one thing to take good digital pictures on land, but in the water its another game altogether.
In this series of articles, we plan to look closely at using a digital camera to record your underwater adventures. Here we deal with the basics, but later we will delve into the hardware - cameras, housings and accessories - and offer tips and tricks on getting the best pictures under water and improving them on your computer.
The whirlwind development of digital cameras in the past four to five years has been comparable to that in mobile phone technology. Cameras now have more functions and gadgets and higher resolution, yet cost less than ever before.
Digital is attracting many amateur divers who would otherwise never have tried underwater photography. You take a camera on holiday anyway, so why not buy a housing as well, and take it under water (Apart from the risk of flooding it, of course.)

In a traditional camera, the light-sensitive plate is the film. In a digital camera, its a chip. As with film, quality and resolution are the important factors to consider. Digital cameras have built-in programs for translating the information received by the chip.
The light-registering area on most digital cameras is less than that on a traditional camera, so pictures are in effect cropped around the edges. For example, with a good 20mm lens on a single lens reflex camera, a 35mm film will produce dramatic wide-framed pictures, but the same lens on a digital camera has a visual field that equals a 28mm or possibly 35mm focal length, depending on the chips size.
We are now beginning to see the first digital cameras with full-frame chips, offering the same picture size as slide film. The only drawback is the price -4200-5800 for the camera body alone!
Nikon, among others, has found ways of getting around the problem. It produces a series of special lenses for digital cameras equipped with cheaper and smaller chip formats.
The relationship between chip size and the focal length of the lens is decisive. Underwater photography relies on minimising the distance between camera and subject, so wide-angle lenses have an advantage, and few of todays digital cameras can compare in picture quality with a good analogue cameras fish-eye lens. Thankfully, however, they can do many other things.

Professional photographers shell out heavily for top-quality lenses. With lesser-quality products, its irrelevant if they are mounted on a digital or analogue camera -- the result will be less sharp pictures.
On digital cameras, the sharpness of the image produced by the lens is the defining point of quality. The lens projects an image of the subject onto the chip and the image responds with a smaller image size than that to which many photographers are accustomed.
Several of the most popular consumer cameras do not allow the photographer to change lenses. Instead, they have other gadgets such as zoom, or the ability to take extremely close macro pictures. On a few models, lenses can be attached to the camera housing when they are not being used, or shoved into a BC pocket.

The pros
What advantages do digital cameras offer over analogue under water Immediate control over the pictures is the first. Learning from ones mistakes is important in underwater photography and the more pictures you take, the quicker youll take good pictures consistently.
With digital you dont have to wait long to examine the fruits of your labour - you can examine your shots on the LCD screen while youre still in the water, or during surface intervals. The screen functions as both viewfinder and a monitor to show pictures already taken. With analogue, by the time you see the results its often too late to change anything, and you may not remember by then how you took the picture in the first place.
An LCD viewfinder makes it easier to compose a picture than with a traditional camera viewfinder. Holding it up in front of your dive mask is no longer necessary - just stretch out your arm while holding the camera to compose your picture.
Its easy, provided there is no strong sunlight shining into the LCD.
This is a great advantage in cramped quarters, where the subject is hard to reach. Besides, having to shove your whole head in behind the camera tends to scare off all those timid little fish.

Free film
If you shot your last frame just as a school of barracuda was about to form into a perfect spiral, with the sun and whale sharks in the background, you will understand the benefit of a digital camera being able to hold a vast quantity of exposures.
The number of shots is limited only by the size of the memory card and the resolution you choose. You could have 100 shots recorded on every dive, deleting all the unsuccessful ones as you go, so the risk of your memory card being full is seldom a problem.
Besides that, you save money. Film needs to be purchased, developed then scanned or printed, and every analogue film is associated with expense two or three times over.
Digital pictures cost money only when you print them. And they can easily be copied and sent, for example by email.
Gathering multiple pictures in the camera, you need to open the camera housing only perhaps once a day, not after every dive. Each time you open the housing increases the risk of leakage.

Moving pictures
Occasionally you discover things in the water that cry out to be recorded as moving images. It may be a dolphin showing off its impressive underwater acrobatic skills, or just a playful crab. Thats when you appreciate having a video mode on your digital camera.
There may be drawbacks in both quality and the length of video sequence you can produce, but its a fantastic possibility to have.
Another advantage of the digital camera is its ability to compensate for the absorption of certain colours that occur in the water. This is referred to as white balancing. Digital cameras usually have a few basic adjustments such as for sunshine, cloudy or night pictures, but white balancing can be adjusted manually on more advanced cameras.

The cons
We should also list the disadvantages of digital cameras. Many models are affected by a phenomenon called shutter lag, a lapse between the moment you push the button and the camera deciding to take the picture. The camera has to make many calculations before it can expose the shot, and though we are talking about a few milli-seconds, it can still be irritating.
Shutter lag has little relevance if youre photographing a wreck, but when it comes to a clownfish frolicking among anemone tentacles, such delay can mean plenty of pictures of tailfins disappearing out of the cameras visual field. Eventually you learn to press a little ahead of time to make up for the delay.
Digital cameras are also less capable than analogue of reproducing light pastel shades close to white, especially if the picture is slightly overexposed.
The buttons and knobs combined with the menu on the LCD window can be almost impossible to adjust with thick gloves, frozen fingers and perhaps a touch of narcosis.
Batteries Digital cameras use a lot of battery power and the LCD tells you their content but not their quality.
Finally, for the best results you need to download your pictures onto a computer with a properly calibrated monitor.

Thunder and lighting
Every book about underwater photography has a chapter explaining the waters ability to absorb light and filter colours, requiring the use of some form of flash at greater depths.
This is probably the main problem for beginners, who are disappointed to see their pictures emerge in an overall washed-out blue or green shade. The lustrous colours that professionals achieve in their pictures is lacking.
Water also filters out surface light, which is why colours tend to look more muted the deeper you dive.
Even in the clearest of blue waters, red and yellow soon disappears from pictures if you dont use flash.
With digital cameras, white balancing can compensate for some of this effect, but use of flash is the best solution. In dim light, or to lighten shadows in direct sunlight, most cameras have a built-in flash that works like a charm - on land.
Under water, it wont do much for you, the reason being that it is water rather than air between the camera and its subject.
The flash tries to illuminate the surrounding waters and merely meets all the particles floating there. The camera detects only these illuminated particles and shows them as the fuzz spots we refer to as backscatter.
The solution is to use a separate flash, mounted on the camera so that it lights from the side towards the subject.
There are two ways in which the camera can control this separate flash. Many digital cameras come with a flash shoe or contact from which to attach a cable to the flash, but an elegant solution is also available for smaller cameras that dont have such connections.
Ikelite, Sea & Sea, Inon, Subtronic and Epoque among others are now advertising digital flashes. The name is misleading, because the flash itself is not digital. The trick is that when the cameras built-in flash operates, the external flash photocell reacts to it.
The camera flash is not needed for illumination, so is shielded by a small wing on or inside the camera housing.
Digital flashguns are not TTL (through the lens) automatic. The amount of power used has to be manually controlled by you, though you do have a very wide range of power settings from which to choose.
A final possibility, for extreme close-up shots, is simply to use a dive torch with a steady light.
This makes composition easier, as you can see how the light will fall on your subject before taking the picture. What you see is what you get.

The chip in a digital camera is designed in a chequered pattern made up of minuscule light-sensitive elements called pixels. Relatively large chips with, for example, 2000 pixels in one direction and 3000 in the other, are called 6 megapixel chips (2000 x 3000 = 6 million).
The chip itself cannot distinguish differences in colours, hence the need to separate those 6 million pixels into at least three categories, giving sensitivity for red, green, and blue respectively.
Often photographers use two green categories, as one is there to control the contrast. Rarely is the full capacity of the chip useable, because the relationship between lens and chip does not allow the light to register right out to the edge of the chip. So in reality the 6 megapixel chip ends up being equivalent to 1 or 1.5 million pixels.
The chip registers raw data which is interpreted by the cameras software. The camera then calculates a higher resolution from the information received. The software increases the physical size of the picture by taking a cross-section of the surrounding pixels, and guesses its way to an image that resembles the original.
This method is known as interpolation. Scanners and picture-processing programs such as Photoshop use a similar method. Used properly, it can give far larger picture files without compromising on picture quality.
Thats why it can be misleading when ads compare digital cameras on the basis of pixel dimensions. A camera with a lot of pixels can be less effective than one with fewer - if its software overworks the picture information.
Your best bet is to see a test picture from the camera you want to buy.

  • Next month: Choosing the hardware

  • Digital
    Digital camera memory cards keep getting smaller in size and larger in storage capacity. Choose cards according to speed as well as size, as this determines how fast the card can store the data before it is ready for the next shot. Most cameras also come
    A typical budget-priced digital camera which came out well in Divers group test (Cheap Shots, April 2004), the Olympus mju 410 is a 4.0 megapixel camera that costs£375.
    Loss of colour with increasing depth.
    This picture is taken without flash at 15m. The water is clear and the sun bright but you see only blue tones.
    The colours are recreated using flash
    The various CCD-chips are a lot smaller than traditional 35mm film.
    Light that appears white can have several nuances of whiteness. The sun, a lightbulb or a fluorescent tube all seem to give off a white colour, but the difference in colour between sunlight and light from a bulb is equivalent to that between white paper and orange peel, while fluorescent tubes actually give off green light.
    All three light sources have varying light characteristics which our brains, and digital cameras, are able to interpret. Topside, adjustments occur automatically on most digital cameras, so normally we never have to think about them.
    The cameras electronics calculate the white balancing by limiting how the colours separate in the picture and, from there, guess which adjustments are required.
    In the water, a digital cameras program for calculating the white balance can be misled. On several cameras you can remedy this by adjusting the basic manual settings.
    While taking pictures in shallow water in sunlight, for example, you can specify the daylight setting. In deeper waters, you can achieve richer colours and dampen blue nuances by using the cloudy setting or its equivalent.

    This picture shows how the reduced colours under water cheat the camera.

    Here it benefits from the digital cameras ability to adjust the white balance and produce more natural colours

    Pixels150dpi print
    (For personal use)
    300dpi print
    (For publication)
    1 MP22 x 16 cm11 x 8 cm
    2 MP27 x 20 cm13 x 10 cm
    3 MP34 x 26 cm18 x 13 cm
    4 MP39 x 28 cm20 x 15 cm
    5 MP44 x 33 cm22 x 16 cm
    6 MP48 x 35 cm24 x 18 cm