WHY DO YOU GO DIVING
It used to be to see what you could bring back; some brasswork off a wreck, perhaps, or something for dinner. Nowadays every diver seems to sport a camera, and that’s because the digital revolution is as much in evidence under water as it is on land.
The fact is that it’s never been easier to bring back images of what you’ve seen to show your friends, whether it be still photographs or video clips, and you can spend from a few hundred pounds on the hardware to many thousands. It’s all very bewildering. Here we attempt to unravel the solution to your photographic needs.
The question is, what are your pictures intended for Will they be for personal or for public use Do you want to look at them on your computer only, in which case 72dpi will do, or do you want to make big prints and therefore need 300dpi
Are you hoping that your pictures might make it into a publication
Remember, pixel count (MP) is only one aspect of the measurement of picture quality. Sensor size is just as important if you want to avoid grainy-looking images in low-light conditions. So compare the MP-rating only with like-for-like sensor sizes.

PHONE CAMERAS
Well-known chains of camera shops such as Jessops are going out of business, thanks to people abandoning their compacts for smart phones, and you can now buy an underwater housing for many of the high-end phones such as the iPhone4 and even iPhone5. You can’t call anyone, but you can use its camera function under water.
Housings for iPhones and Android phones by the likes of Patima and iGills will soon be common sights at dive locations.
The flip side of this is the imminent arrival of Smart cameras, which run mobile operating systems but feature much larger sensors and zoom lenses. These could threaten Apple’s iPhone dominance in the field of mobile photography.

POCKET VIDEO & STILLS
The GoPro camera, in its latest incarnation as the Hero HD3 (from £200 to £360 approx) is a tiny box that fits into an equally tiny underwater housing.
You can shoot stills or video with it, and people are strapping them on to themselves before doing any type of ridiculously dangerous thing before uploading the record on to YouTube.
Scuba-diving may be a little tame by comparison. Predictably, there are alternative makes of similar cameras making inroads into this rapidly developing market, such as the Liquid Image Ego (£210 housed) and the same company’s Camera-Mask (£330)
The funny thing is that it’s more difficult to get good footage under water than it is free-flying from the top of a mountain, although certainly less dangerous.
That’s because the light under water is distorted, with the longer wavelengths from the surface filtered out.
You need a colour-correction filter if you’re shooting in the shallows, but if you want to get good images deeper you’ll need to take an even, powerful source of white light with you.
The same can be said of any camera. no matter how much you spend, unless you’re content with monochromatic pictures.
It might be a continuous light source, essential for movie clips, or an underwater flash that outputs a lot more but only for an instant, but that is what you’ll need if you want sharp still pictures. The bigger the camera you use, the brighter a light will be required.

AMPHIBIOUS CAMERAS
There are a few truly amphibious cameras that are rated to go to scuba-diving depths. The 9MP SeaLife Mini at £239 is one of them. It comes with its own wide-angle wet lens and will shoot both stills and video, but although a full range of accessories is available for it, it really is an entry-level camera.

COMPACTS
When you want to advance to something better than the SeaLife Mini, you could look at the SealifeDC1400 Pro outfit, complete with automatic off-board flash (£799), but this is in fact a separate compact camera in an underwater housing.
Many of the compact cameras available today from the major manufacturers can be supplied with a proprietary housing made of heavyweight plastic, and because these little cameras have zoom lenses that can be turned into macro lenses at the push of a button, they are very versatile instruments for divers.
Extreme close-up photography is where every new underwater photographer starts. The rule of underwater photography is to exclude as much water as possible from between your camera and your subject.
Close-ups naturally allow you to do this, and your lighting is effective when it’s close, too.
Canon, Fuji, Nikon, Olympus, Panasonic and Sony all make useful compacts that can be installed in underwater housings.
The state-of-the-art compact cameras popular for use under water (at the time of writing) are the 12.1MP Canon Powershot G15 (around £300), the 20.2MP Sony DSC RX100 (at around £450) and the well-established 12.1MP Canon Powershot S110 (approx. £383).

WET LENSES FOR COMPACTS
Shooting larger subjects demands a wide-angle or fisheye lens. Often, these ancillary lenses are made by third-party manufacturers such as INON, Zen and Nauticam, but you must be sure that the housing you buy for your camera will accommodate them.
As a rule, the better-quality underwater housings are made by third-party manufacturers. Ikelite, Nauticam, Fantasea and Patima are just some of them.
The compact-camera market is quite mercurial. It’s best to buy camera, housing and additional wet-fitting lenses at the same time to be sure that all are available when you want them. Wet lenses can cost from £250 to £400.

SYSTEM COMPACTS
The bigger the camera’s sensor, the better the quality of the pictures will be. Compact cameras have sensors that are tiny.
The new breed of camera now finding favour is bigger than a compact, has a bigger sensor and the advantage of interchangeable lenses. Such cameras are known as “four-thirds”, which reflects the proportions of the sensor, or “mirrorless”, because they are larger than compacts but smaller than DSLR cameras that use a mirror.
Some people call them compact-system or system-compact cameras, because of their versatility.
The Nikon 1 (£250 with 10-30 lens), Sony a-NEX 7 (body only £500), Panasonic Lumix GX1 (£350 with 14-42 lens) and Olympus PEN E-PL5 (up to £720 with 14-42 lens) are all examples of these cameras for which underwater housings are available.
The best-equipped ones even give you an electronic viewfinder, viewed in the same way as a DSLR. These are called “micro four-thirds” cameras. The 16.1MP Olympus OM-D E-M5 (around £850 without lens) is likely to take the underwater photography market by storm in this category and looks at first glance like a smaller DSLR.
Nauticam and INON are probably the leading manufacturers for housings for this group of camera, although Olympus makes its own housings too.

BIG-SENSOR COMPACTS
There are some compacts that use large sensors for great low-light performance. The 14.3MP Canon G1X (£500) was the first of these, with a sensor size approaching that of a DX camera. Alas, it doesn’t focus very closely, which precludes it from use under water.
However you will soon be able to get a full-frame compact. The fixed-lens 24MP full-frame FX Sony DSC RX1 promises to knock spots off all other compacts. It should do, because it will cost around £2500! We’ll need to wait to see whether an underwater housing will be made for it.

DX DSLR
Digital single-lens-reflex (DSLR) cameras allow you to look through the lens of the camera via a mirror and a pentaprism and record a picture almost the instant the shutter button is pressed. They have the versatility of interchangeable lenses and the quality of a larger sensor. The DX types have a sensor of around 18x24mm.
Of course, the bigger the sensor, the more expensive the equivalent lens will be, because it needs to cover a larger area inside the camera. Popular DX format DSLR cameras are the 24MP Nikon D7100 (around £1200) and 18MP Canon EOS 7D (£1700). Prices do not include lenses.

FX DSLR
Keen underwater photographers spend all their money on full-frame (FX) DSLRs that have a 24 x 36mm sensor, the same size as a old-fashioned frame of 35mm film.
These are the biggest sensors currently available in the consumer market, and offer the highest-quality pictures.
They cost a lot to buy, as do their lenses, but they can produce stupendous-quality pictures with grain-free results in 64 times less light than a typical smaller camera.
Manufacturers, aiming to differentiate their models from the new micro four-thirds cameras, have introduced some entry-level FX cameras, notably the 24.3MP Nikon D600 and 20.2 MP Canon 6D (both around £1200 for body only).
It is thought that these entry-level FX cameras might eventually replace the DX DSLR category in the marketplace, shooting both high-end stills and HD video.

THE PROFESSIONALS’ CHOICE
Two manufacturers are currently fighting it out for the favours of top underwater photographers: Nikon, with its popular 36MP D800 (around £2500), and Canon with a newly revised 22.3MP EOS 5D MkIII (at around £3000). These are appropriate for those divers who expect to see their pictures printed at any size or cropped tightly by magazine art editors.
Add the price of the lenses, which can cost anything upwards of £400 each, and a housing with ports that can cost around £3500, and you’ll appreciate that these pros go into the water with kit costing the sort of sums that make insurers tremble.

TOP-END UNDERWATER HOUSINGS
When it comes to underwater housings for these high-end cameras, whether they are micro four-thirds, mirrorless, DX or FX format, they have to be tailor-made so that the controls can be accessed from outside the casing, and this is inevitably reflected in the cost.
Because camera models change so frequently, independent submarine housing manufacturers have very short production runs, and sometimes this means ordering one and waiting for it to be made.
In alphabetical order, typical housing brands include Aquatica from Canada, Hugyfot from Belgium, Ikelite from the USA, Nexus, Sea & Sea and Olympus (for Olympus cameras) from Japan, Nauticam from China, and Seacam and Subal, made in Austria.
There are other makes but these are the most popular among underwater photographers at the moment. The prices vary from those for system compact cameras to those for top-end DSLRs – in other words, from around £1000 to as high as £4000. Then you will need a lens port specifically matched to the lens you intend to use.

UNDERWATER LIGHTING
If you want to shoot video clips, a continuous light source can cost from around £200 for a basic 600-lumen white light source to more than £1000 for a 10,000-lumen Swiss-made lamp.
Illustrated are the FIX 7000, the Solar 2000 and the Keldan 4000 and, of course, there are many more examples of different makes available.
Underwater flashguns range from £200 to around £800 for a state-of-the-art version and you’ll need two, with the mounting arms to go with it. INON, Ikelite and Sea & Sea are the main protagonists.
The cost mounts up once you start buying cameras, lenses, underwater housings, lens ports, underwater lighting and mounting systems. Then you’ll need the computer and software to make the most of the pictures you take.

Thank you to David Glanfield and Mario Vitalini of Ocean Leisure Cameras for their assistance in researching this feature. www.oceanleisurecameras.com

THE MAIN QUESTIONS
What size is the sensor
The bigger the sensor, the greater the low-light capability. Megapixel count can give an indication of the size of pictures that can be produced without pixels showing, but digital noise (unsightly grain) is influenced by the ISO (sensitivity) setting. A small sensor with high MP might be limited to low ISO settings.

How closely does it focus
Refraction between water and the air in front of the lens makes subjects appear much closer than they are. You need to know that your camera will focus on your intended subject once you are under water with it.

Does it shoot in RAW mode
RAW files allow the photographer to make a lot of photographic decisions on a home computer long after shooting under water. However, with cameras that have no internal buffer, it can mean a few seconds delay before you can take the next shot if you shoot in RAW mode – a vital consideration when photographing marine life.

Is there an ancillary wide-angle or fish-eye lens to fit the housing
Compact cameras need the additional help of these important accessories when photographing anything other than macro (extreme close-up) subjects.

Which front port do I need to suit my choice of lens
With cameras that have the advantage of interchangeable lenses, you need to be sure that a port matched to your choice of lens is available. Sometimes a spacer ring is needed to position the port in the right place relative to the front node of the lens.

Are all the camera functions I need available once it is encased in the underwater housing
Zoom lenses need gear-rings fitted to enable that function. Macro lenses need their auto-focus function to be switched on or off as needed.
There’s nothing more frustrating than to find that the button you need on a housing to operate the camera is not there!

Which memory card does the camera use
Popular memory cards are either Compact Flash (CF) or SDHC. A few cameras use proprietary cards from their manufacturers, and these might prove difficult to source in remote locations.