Choosing a digital camera

With so many models from so many makers on the market, picking the one that’s right for you can be difficult. Here’s a brand-free guide to making a good choice.


The first thing most people look at is pixel count, reasoning that more pixels are better. Within limits, that’s true, but once you get to five or six million pixels you’ve got enough to make detailed A4 prints, and far more than you need for on-screen viewing. More pixels may permit better detail resolution, but they also mean more image noise.

The sensors on compact cameras are tiny, and the more pixels that are crammed in the smaller each pixel has to be, or the closer it is to the next pixel along. Pixels work by converting the light they receive to an electric charge, and if the pixels are too close together the charge can leak from one pixel to the next, creating digital noise. The camera makers get round this by building-in noise filters, but these work by slightly blurring the detail to cover the noise up. Effectively more pixels capture more detail, which is then lost in more aggressive noise filtering.
The situation is always worst at the top of the resolution scale, and eases over time as the designers improve their noise filters and production techniques.

The best sensor resolution probably comes from second or third generation sensors that offer slightly fewer pixels than the current top of the line models. If the current headline grabber is 10 million pixels, go for a second or third generation 7 or 8 million pixel model.



Next, look at the camera controls. The underwater environment is different to the world above water, and the advanced exposure control modes of most land cameras may give poor results below the water. At the very least you should have some form of exposure over-ride, so if pictures come out dark you can increase the exposure, and if they come out light you can decrease it. If you think that you’ll get into underwater photography in a serious way go for a camera with a full manual mode. Manual is a bit long-winded to use underwater but once you’ve used it for a bit you’ll get better results more reliably. If the camera has a manual mode it will have the full range of auto-modes as well.


One control that you really need is manual white balance. As you dive deeper the red progressively disappears from the light, then other colours until you’re left with just blue or blue-green. To a depth of about 10 metres you can adjust the white balance to boost the red and record good colour, and deeper than that you can add colour correcting filters that allow you to do the same.


Then check the camera focus distances. Many cameras offer macro and super-macro modes. If you want an all-in-one solution these are useful, though add-on macro lenses are more usable in practice. Macro, or close-up, is a good way to start underwater. Even if the vis is awful you can shoot macro, and in close-up work the camera auto-exposure system is likely to give accurate results.


The ability to record RAW or jpeg files is another feature to look for. Shooting in RAW mode allows you to set the colour balance after the dive and get more natural looking colour, and you can also rescue over- or under-exposed shots, provided they’re not too far away. You can also do both these with jpeg, but RAW will allow you to make bigger corrections without loss of picture quality.



After you’ve picked a camera you’ll need to house it. The housing should allow you to use all the camera functions below water. Manufacturer housings tend to be rated to 40m, though Ikelite make a range of 60m housings for compacts.


The important thing to look for is some way of attaching an accessory wet-mount lens. Olympus housings, for example, have a screw-thread adaptor on the front, and for housings from a variety of makers Inon do a range of after-market mounts to suit their range of screw-mount and bayonet fit accessory lenses. Ikelite offer adaptors for their housings that allow you to use either screw-fit or bayonet fit wet-mount lenses. Forget any camera/housing combination that doesn’t allow you to add accessory lenses.


Once you’ve decided on a camera and housing, take it diving, then think about adding extras.


Wide-angle adapter lenses can be added and removed underwater. They work by decreasing the focal length of the standard lens on your camera, giving you a wider-angle view. When you’re underwater the field of view of your standard camera lens will be reduced, this is due to the refractive index of the water. Adding a wide-angle adapter gets rid of this effect and will give you a wider field of view underwater than the standard lens on land. This means you can get more of your subject in from the same distance, or can get closer and fit more in. The main reason for underwater pictures looking poor is that they were taken with too much water between camera and subject, and using a wide-angle gets rid of some of the water.


External flashguns, or strobes, are mounted well away from the camera lens. When the internal flash fires it lights up all the debris floating in front of the camera as well as the subject, making the scene seem snowy. This is called backscatter. If the flash is well away from the lens axis the effect is reduced or eliminated. External strobes can also be much more powerful, making your life easier, though even the most potent flashguns won’t throw much light beyond four feet underwater.


Macro lenses mount in front of the main camera lens. Macro mode on most cameras fixes the focal length of the camera lens at the wide-angle setting. This means to take macro pictures you have to be close to the subject, sometimes very close. This makes lighting the subject difficult. A macro lens reduces the maximum distance at which you can take a picture, but allows you to use the camera zoom at any setting, from maximum wide-angle to maximum telephoto. You can get frame-filling macro shots with the camera further away, it’s easier to light the scene and you don’t have to get so close you scare the subject away.



So, if you’re looking around for a camera today I’d suggest an 8 million pixel model with full manual mode and a housing that takes accessory lenses.