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Technical

April 2008

Digital is so advantageous in underwater photography. Viewing your results straightaway under the water is essential to perfecting your image, and you are not limited to one roll of 36-exposure film on each dive. The ability to delete bad frames means that the greatest limitation is either when the battery runs out; you fill your card; or your dive time ends.

The use of autofocus, auto exposure controls, and the ability to take a white balance and change the ISO during the dive all help to free up the photographer to focus on finding the subject, composing and lighting the shots, while being careful not to damage the precious aquatic life.

© Helen Atkinson

Silhouette on wreck shot from below towards light source (the sun) coming through water from above.

High-end Canon EOS digital SLR cameras have a major advantage over other digital brands and compacts in this field because of the superior file sizes and advanced chip technology. When under the water shooting up directly towards the source of light (like the sun) sensors from many digital cameras cannot handle the high differential in exposure between the light source and the surrounding landscape, also there are often difficulties in capturing the rays of light radiating out of the light source.

Downloading your images to a computer after the dive means the data storage device is free for the next dive. This also allows for image optimisation, and enables the photographer to share the dive experience with others. But don’t expect to get perfect images first time out - you can only improve with patience and plenty of practice.

There are several key factors to consider when choosing your underwater photographic equipment. They include the size and weight of your kit, whether you’re shooting using film or digital, ease of use, travel involved, maintenance, cost, the depth you’ll be shooting down to, and intended use.

In my experience in an underwater photography kit you will need your camera (of course), a suitable housing, a solid travel case, dive gear, a wideangle or zoom lens, a macro and long lens, filters, flashguns, grease, and some spare o-rings.

© Helen Atkinson

Seahorse shot close-up amongst coral.

One of the best places to start your search for underwater photography equipment is the online directory www.digideep.com - this informative site has a full listing of Canon cameras and available housings, as well as a guide to the distributors of the equipment around the world.

For information on Canon’s housed cameras go to www.canon.co.uk, and online forums such as www.wetpixel.com will help to guide you on what equipment to get.

Canon makes its own plastic/acrylic housings for some of its compact camera range with prices for these starting from around £50, but it doesn’t make housings for its EOS SLR cameras (digital and film models). But fear not as there are many EOS housings available which are manufactured by third party manufacturers such as Ewa Marine, Ikelite, Aquatica, Sea & Sea, Subal, and Seacam, and can deliver waterproofing to depths between 30-90 metres (100-295 feet). You may prefer to have custom-made housing for your camera and retail prices for these housings range from around £140 to in excess of £4,000 depending on your specific requirements.

High Street retailers will stock some compact housings, but for a good range of housings for compacts and for the larger DSLR housings you’ll have to go to a specialist such as www.camerasunderwater.co.uk, www.oceanoptics.co.uk, or www.underseacameras.com.

© Helen Atkinson

Aquatica housing for the EOS 5D.

Whether you like diving deep beneath the ocean’s waves, snorkelling around the shallows, swimming, or just splashing around, there’s a camera system to suit your needs, but size does matter! Most people expect a large digital camera in housing to be heavy in water and sink, but the air inside the camera housing means that most tend to float a bit – this is known as positive buoyancy.

Adding extra weight to the housing will offset this buoyancy, however, and out of the water a fully rigged underwater EOS system with external flashguns can be quite heavy and cumbersome to carry to and from your dive site or dive entry point, especially when wearing all the scuba gear! So finding an easily accessible dive site is important for a stress and exhaustion free dive.

Ewa Marine (available from Cameras Underwater) makes very lightweight, flexible underwater housings from thick PVC containing additives that make them resistant to UV and IR rays. The edge seams are electrostatically welded and the opening (for the camera) is sealed with a pair of non-corrosive clamping rails and can be tightened by three screw knobs. The integrated front port is made of optical grade neutral flat glass, and with a special adaptor for autofocus SLR models this front port rotates with the lens when you’re shooting in AF mode.

© Helen Atkinson

Rays pictured on the seabed.

At about £190 the U-AXP model fits most SLRs and some DSLRs including the EOS 400D, EOS 450D, EOS 40D, and EOS 5D without grip. The U-BXP will fit larger DSLR cameras such as the EOS 5D with grip, EOS-1D Mark III, and the EOS-1Ds Mark III. Both of these housings also have space inside the housing for an external flash such as the 580EX MKII on top of camera.

Before using Ewa Marine housings it’s important to make sure that the camera and lens are properly centred (foam padding may help with this). Make sure that the lens is as close as possible to the port, otherwise there may be problems with vignetting and focusing, and that the seals are closed very securely! The high buoyancy of these housings can be lowered with the addition of lead weight, although this will vary depending upon depth and pressure you're diving at.

The camera is operated through the plastic, although with smaller buttons this can be awkward, and without magnification on the camera’s viewfinder composing and focusing on your subject can be hard, especially when wearing a mask or goggles. The clear plastic allows viewing of the whole camera both for operation and to check for leaks and condensation, and is also easy to wash and clean.

© Helen Atkinson

Bubbles shot from below showing underwater photographer with lighting rig and natural light from above.

Ewa Marine housings are suitable for snorkelling and are apparently safe to much deeper depths. This is because the air inside these housings is compressed under the pressure of water (i.e. more compressed at greater depth). Thus they have recommended depth limits for safe operation of the camera, although I haven’t tested this myself!

Polycarbonate housings generally have a front and back moulding with a separate lens port, and use o-rings to seal the joints between mouldings and ports. They are less expensive than aluminium models, are corrosion free, and provide a full vision of the o-ring seals and camera inside. However, they can be very large.

The Polycarbonate (Lexan Acrylic) Ikelite housing has designs specific to Canon’s bodies, including the EOS 400D and EOS 5D, and are sized and weighted for near neutral buoyancy with a camera inside. The clear acrylic also allows for an unobstructed view of the camera’s controls, as well as easy visual inspection of lens port, and there are back door o-ring seals for leaks or condensation.

© Helen Atkinson

Ikelite housing with soft cover.

Aluminium and alloy housings are generally more expensive than polycarbonate ones. But they are more durable, more robust, better able to stand up to hard use, and tend to hug the shape of the camera much more. Manufacturers such as Subal, Seacam, Sea & Sea and Aquatica have specific designs for Canon’s DSLRs, including the EOS-1D and EOS-1Ds series. However, if the housings aren’t thoroughly washed in freshwater after immersion in seawater they can corrode. The view of the camera inside aluminium housing is minimal, (just views for taking and viewing the picture), so if you’re worried about leaks or condensation then I recommend using silica gel or fitting a leak detector.

The ergonomics and external camera controls of the dedicated housings mentioned above are especially good on both aluminium and acrylic models. This is extremely important for comfort and ease of operation, but in all cases it does help to memorise which button or lever does what so you can concentrate on capturing the image.

© Helen Atkinson

A Trigger Fish approaches a diver’s mask.

Viewing your subject and composing your picture through the viewfinder of any housing with a dive mask between you and the camera can be very difficult. Adding a magnifying eyepiece to your housed EOS system such as Ikelite’s ‘Super-Eye magnifier’ (included in housing), or Subal’s add-on ‘GS 180’ finder will enhance your view, so you can compose and focus your subject more easily.

Lens ports are not usually interchangeable between manufacturers, and are usually an additional cost to the front and back mouldings, but they are an integral part of your EOS housing as they allow you to use a wide range of lenses from fisheye to macro, long lenses and zooms.

There is no single best lens for underwater photography, but generally speaking it is better to have less water between the subject and the lens therefore you are more likely to achieve good results with wideangle or macro lenses.

The lens port acts like a window on land, but once in water it behaves very differently due to the refraction of light in water. Generally this causes most objects to be magnified and appear closer than they really are. Consequently this creates a closer virtual image for the camera to focus on, which therefore changes focal lengths.

© Helen Atkinson

A dome port for the EF-S18-55mm f/3.5-5.6 wideangle zoom lens.

The two main types of lens port are: flat port for macro or longer lenses, and (hemispherical) dome port for wideangle lenses (usually those wider than 35mm, but now accommodating zooms such as the 18-55mm). Both types generally attach to the front moulding using a bayonet-type fitting, sealed by a radial o-ring for rapid lens changing.

Glass ports are arguably optically better than polycarbonate and scratch less easily. However, it is easier to repair scratches on the cheaper acrylic ports, which also don’t tend to mist up, unless left out in the heat and sun. Using silica can help to alleviate this problem.

Refraction in underwater photography causes a degree of optical pincushion distortion and chromatic aberration (see the glossary at the end of this article). This can be minimised by using the correct combination of lenses and ports for the subject you are picturing, thus having a more equal space between the focusing points of the lens and the port.

If necessary any distortions that occur can then be corrected afterwards using specialist computer software or Photoshop plug-ins.

The dome port is used to maintain the angle of view with wideangle lenses. This allows for very close subject distances, which decreases the in-water light path and improves image brightness and colour saturation. It’s ideal for photographing wrecks, coral vistas and large sea life.

© Helen Atkinson

Helen Atkinson neutrally buoyant and approaching rockfish cautiously to avoid damaging her aquatic surroundings.

The curvature of the dome minimises refraction and also eliminates the problem of vignetting (especially with fisheyes) that the flat ports give with wide angles, so for this reason purpose-built DSLR housings accurately centre the camera and lens to the dome ports.

When focusing, the virtual image of your subject appears much closer to the camera, and therefore requires the lens to focus at short distances. This point is roughly a foot in front of the dome. This also causes the image to have a greater depth of field than indicated on the settings

Ports don’t usually have anti-reflection coatings, so a lens shade will protect against lens flare from either the sun, or when using flash lighting, thus improving the colour and contrast of the photo.

Lens shades are normally dedicated to the wideangle port they are designed for, but can be removed if required (either for shooting or for travelling). A neoprene or soft polyethylene cover will protect the glass or acrylic port against scratches and damage when not using, or during transportation.

© Helen Atkinson

Close-up of rockfish with lighting from underneath shot at a depth of 20m.

My top tips for underwater shooting are…

  • Have fun
  • Don’t take unnecessary risks
  • Try and find a dive buddy who is interested in photography or at least one that will hold a torch for you
  • Check that the dive centre will accommodate underwater photographers
  • Know your camera – for ease of operation
  • Keep spare O-Rings and batteries with you
  • Preset your camera before moving closer to subject
  • Watch where you put your hands
  • Keep an eye on your air and time
  • Think and consider each photograph before you shoot
© Helen Atkinson

Close-up of an eye of a lobster.

By taking the pace of your dive slowly you’ll easily find sea life around shipwrecks, coral reefs and rocks. Attaining good buoyancy and avoiding kicking up sediment from the seabed will also aid your pictures and reduce backscatter.

Watch out for dangers such as sharks and jellyfish, and if you do decide to work without gloves for greater ease in operating the camera equipment, be careful not to scratch your hands on rocks and coral, or damage the marine life.

When you’re concentrating on taking your pictures it's easy to be distracted by your subject and get disorientated or lose your buddy. Be patient and think before you shoot. Don’t forget to keep an eye on your air and dive time, depth and current, as well as that of your buddy to avoid running out of air and decompression problems.


Be prepared for the unexpected both in the environment you’re in and with your equipment and don’t panic when things don’t go to plan. Just remember if you’re feeling uncomfortable with the situation you can always abort the dive and return safely to the surface.


Underwater photography - key terms
Acrylic Poly methyl methacrylate. A clear plastic with good optical properties. Used for many dome ports.
Backscatter light reflected in the lens from suspended particles in the water (looks like snow in photographs).
Buddy your scuba diving partner (and essential underwater photography assistant).
Buoyancy control the ability to control where you are in the water.
Chromatic aberration the formation of coloured fringes on an image due to the differences in refraction of different wavelength light by a lens. An achromatic lens may be used to correct this aberration.
Diopter a unit used to express the power of magnifying glasses. Also used as a name for screw in magnifying lenses, which can be fitted to the front of a camera lens.
Dome port a semi spherical piece of acrylic or glass used to eliminate the magnifying distortion caused by reflection – this attaches to the housing and encases your wideangle lens.
Flare unwanted streaks of light on your photos caused by lens imperfection and/or pointing the camera at the light source.
Flat port a flat front element of acrylic or glass and tube which encases your macro or long lens and attaches to the housing.
Fogging misting up of the port element due to condensation inside the housing.
Housing an acrylic, aluminium or alloy watertight box that encases your SLR camera.
Macro lens an extreme close-up lens.
Neutrally buoyant the position where you neither sink nor float.
O-rings silicone, synthetic rubber or neoprene rings used to seal joints in underwater camera equipment making them water tight.
Radial distortion alteration in magnification measured from the centre of the len’s field of vision outwards in a radial direction.
Refraction bending of rays of light as they pass from one medium into another, for example from air to water or air to glass.
Wideangle lens lens that has an angle of view significantly wider than a normal human perspective, typically less than 28mm (on a 35mm SLR system).
Further reading & viewing
The Underwater Photographer by Martin Edge
Underwater Photography by Paul Kay
An Essential Guide to Digital Underwater Photography by Michael Aw and Matthew Muir
Water Light Time by David Doubilet
Diving the World photography by Norbert Wu
Dive Atlas of the World: an illustrated reference to the best sites edited by Jack Jackson
Coral Reef Adventure (MacGillivray Freeman’s) high definition DVD
Recommended dive sites
Australia, Great Barrier Reef www.prodive-cairns.com.au
Canary Islands, Lanzarote www.rubicondiving.com
Global, Padi Dive Centres www.padi.com
Greece, Parga www.poseidondiving.gr
Jordan, Red Sea, Aquaba www.rdc.jo
Nungwi, Zanzibar, and Tanzania www.sensationdivers.com
UK anywhere with a drysuit!