Underwater camera system guide

It is hard to say whether equipment is the solution, or the problem, for underwater photography! There is a confusing amount, and variety, of underwater photographic equipment on offer. We have, therefore, prepared this guide for both the uninitiated and those who just seek to upgrade. It will take you along the various routes open to you when buying underwater cameras and lenses, whilst also giving an overview of what equipment can (and cannot) do for you.

Let’s face it, a camera is essentially a simple device - merely a light-tight box with a lens at the front, a system for transporting film at the back, and a method of controlling the amount of light in between.

Underwater cameras must also conform to this basic design, but obviously have to be watertight/pressure proofed too (or be placed in a housing that is). Underwater cameras must be robust, compact, easy to use, and fit into a budget!

In some ways it is easier to start from scratch. Your choice is then simple - you need a camera (with the right lenses), a flash and some means to hold them together! If you already have a piece of equipment however, your options are limited to other items that are compatible with it.

Whatever your starting point you must realise that everything to do with underwater photographic equipment is a compromise and you need to sort out priorities. You must ask yourself which features you think are essential and which features you think are merely desirable?

The first thing to realise is that you never just buy an underwater camera - you buy a system. Even if you start out with the camera and add lenses, flash, and flash arm later you should consider the system choice as being the most important one to make. You may be surprised - what may have been the obvious choice to begin with may actually be the least effective and most costly in the long run!

WHICH SYSTEM?
The camera is the heart of your system. The basic choice is between a purpose built underwater camera or putting a land camera in an underwater housing. Each route has its advantages (and disadvantages).

The camera housing is the most cost effective way to get the latest technology underwater (and technology means a higher percentage of results). Housings cost more but, when you weigh up the cost of one against the cost of a foreign dive trip, you might be able to justify the extra expense to guarantee coming back with better results. The current trend in underwater photography is towards housed autofocus (AF) camera and this will, no doubt, continue.

Although it takes some time for the current technology found in land cameras to become incorporated into underwater cameras all the essential functions have already found their way into the latest Nikonos and Sea & Sea models - so they will all yield successful pictures if used intelligently. However, as a general rule; the more you pay - the easier it gets.

The alternative to the camera housing is the purpose built underwater camera but, because the market for such equipment is relatively small, the choice of products is limited to only two major players: Nikon (with the Nikonos), and Sea & Sea (with the Motormarine I I and Explora models). If you are just a snap-shooter and cannot justify a major investment outlay for a system (that perhaps you will only use on one dive trip a year) then the Sea & Sea range is the first place to look.

WHICH CAMERA? SLR-V-NON SLR
The main difference that sets camera systems apart is the viewfinder system. The camera in a housing is a Single Lens Reflex (SLR) and has reflex viewing, that is to say, by means of an ingenious prism and mirror system, you can see exactly the image as it is Through The Lens (TTL); whereas, the purpose built underwater camera only has a simple viewfinder to keep costs down.

To avoid confusion (we hope!) we shall refer to underwater cameras as being either SLR or non-SLR. All cameras have some kind of viewfinder but the viewfinder on non-SLR cameras is merely a ‘window’ built in to the camera body (or a slot-in optical lens) which only approximates the actual view of the lens. Unfortunately, with this system, it is very difficult to judge lens coverage, and it is therefore easy to crop your subject accidentally.

Focus must also be achieved by ‘guess-timating’ on non-SLR cameras. You must judge the subject distance and relate it to a scale on the lens. However, with a bit of experience you can get quite accurate, especially with wide angle lenses which are virtually focus free anyway and for macro photography (the photography of smaller subjects) where the subject area is shown by framers.

Although not allowing TTL viewfinding, underwater non-SLR cameras can employ metering systems which measure light (both ambient and, in top of the range models, flash) through the lens. Although not foolproof, TTL metering yields a high percentage of successful exposures in the majority of circumstances underwater. The photographer must, however, still interpret readings in order to balance natural light and flash with this system. The current generation of SLR cameras have, however, gone one step further and now have software which can automatically handle the chore of balancing flash with ambient light.

Both the Sea & Sea and Nikonos are regarded ideal, entry level, non-SLR cameras to start underwater photography and, especially in the case of the Nikonos, an impressive range of lenses and accessories can be added so that it can be the only camera you will ever need to buy. The metering system Sea & Sea cameras employ is not accurate enough to guarantee successful exposures with slide film; an important point if you want to sell your pictures, because most magazines only accept slides. If you want to publish your work you must go the housing route.

CAMERA HOUSINGS

Increasingly, the trend in underwater photography is towards camera housings (even at entry level). The price differential between housed systems and non-SLR cameras is now negligible and when you consider that you always buy a system (not just a camera) then in the long run a housing is usually the best route to go. Land lenses are nearly always cheaper than lenses for non-SLR U/W cameras so, although the initial outlay on a housed system may seem slightly greater, you will save money overall.

There is one distinct advantage in housing a Nikon camera - nearly all the underwater strobes commercially manufactured these days are only Nikon TTL compatible. However, if you own a Canon EOS or Minolta Dynax camera there are housings and underwater flashes available now which give you a system equal to any Nikon (but at a premium).

WHAT TO LOOK FOR IN A HOUSING
There is little point in putting an SLR camera in a housing if you can’t see the viewfinder properly. The problem is that you can’t avoid having your eye forced back from the viewfinder by your diving mask - thus making the average camera viewfinder (which was designed for land use with the eye against it) impossible to see entirely. In order to see the viewfinder image and display information you must move the housing from side to side. To overcome this all the leading manufacturers have a device called a viewfinder optic built in to the rear of the housing. You must be able to see the entire frame for composition. Without an optic you risk cropping your pictures. see below:

with and without a viewfinder optic:

Attention to detail inside a housing is a good indication of quality throughout. For instance the wires onto the TTL socket should be resin sealed in order to protect the terminations, rather than left bare (and open to corrosion).

All housings require a TTL flash socket (usually the almost universal Nikonos fitting) in order to plug in a TTL strobe. As an optional extra you can usually have a second TTL socket fitted to allow the use of two strobes. You should check whether this needs to be done by the factory (necessitating a delay) or whether it can be fitted retrospectively.

You also need some means of attaching a strobe via an arm; either threaded holes underneath the housing to take a tray, or via ‘shoes’ attached to the housing (or on the handles). Most manufacturers are let down by the quality of their own arms. Only one system, Technical Lighting Control (TLC), fit all systems and offer total functionality.

Ergonomics is the so called ‘invisible factor’ in design. Basically it means how well the controls fall to hand. The average SLR camera is designed to be easy to hold and use, with controls falling naturally to the appropriate finger. Unfortunately, all that changes as soon as the camera is fitted into a housing! There are only so many ways that a lever can be made to hit a camera control so mechanical transmission housings are always limited as to how ergonomic they become -especially to the diver with gloves on.

Handles are not vital to the operation of a camera housing but do stop your hand aching, and are particularly handy when passing your camera up to the boat!

HOUSING DESIGNS
The only sensible material to make a camera housing out of is cast aluminium. It is robust, so will generally go deeper, accept accessories better, and has excellent heat sink properties which precludes internal misting in humid climates. Compactness is a major factor in choice of housing for the travelling photographer. The larger a housing is, the heavier it must be in order to remain neutrally buoyant in the water. Bulky units not only take up more space, but also contribute to excess baggage charges and aching arms! The trend now is to build a housing for a specific camera. It can then be constructed to ‘fit like a glove’ and allow you to operate 90%of the cameras controls. Only aluminium housings conform to these specifications.

Most aluminium housings should operate far beyond Sport diving limits (to give a margin for error) which, needless to say, is also well below the depth where interesting subjects are found! Depth rating of housings is dependant upon many variables, such as housing size and wall thickness, O-rings and structural considerations. The depth rating for housings can vary between 40M (perspex construction) and 100M (aluminium).

Most housings are of the clam-shell design, that is to say they split longitudinally down the middle to allow access to the inside. The two halves of a housing should open and close positively, not open accidentally, and without the need of tools. With this brief in mind, manufacturers almost universally install stainless steel clasps these days rather than screws and bolts. Clasp fasteners are pre-tensioned to give the correct closing pressure and there can be no argument as to whether or not a housing is closed properly. It is either open, or closed - end of story! For additional idiot proofing most manufacturers employ the type of clasp with a safety interlock which cannot be opened accidentally.

O-RINGS
The camera housing itself does not keep out water on its own of course. The seal between mating surfaces is made by O-rings (soft rubber rings that flatten out under compression to fill the ‘gaps’). You will find O-rings on the main seal, the Port and on all control shafts that go through the body of the housing. Control shaft O-rings are not user serviceable and it is easy to forget them because you can’t see them. The problem with control shaft O-rings is that, inevitably crystals will form as seawater dries out, and these can abrade the O-ring when you next operate the lever. It is almost universally accepted that, in the fight against water ingress, having double O-rings on all moving parts that go through the housing is essential. Let’s face it, one of the basic principles of diving is that you always have a backup, and double O-rings on all control lever shafts give added security (and longer periods between maintenance). The main clam-shell O-rings do not need to be double as they do not have moving parts in contact with them and are, in any event, user serviceable.

HOUSING TYPES
There are a number of different housing designs. The most basic design relies entirely on autofocus i.e. the ‘capsule’ type housing. The capsule offers only basic control, just a shutter release and TTL flash socket (and is usually a stripped down, budget version of the top of range housing). Capsule housings rely entirely on autofocus and auto-exposure techniques.

There is also a permutation of the capsule housing that takes a number of different models, sometimes called the universal housing (or Uni housing for short).

Some capsule housings have viewfinder optics, some don’t. An optic will increase the cost of a housing by 20% (but also increase functionality by 100%).

Most serious underwater photographers plump for the housings that gives the most control, the so-called Full Function housings. This type of housing allows you to operate the maximum number of controls (within physical limitations).

PORTS AND GEARS

The removable port is an integral feature of the underwater camera housing. There are two basic types, the dome port (for wide angle lenses) and the flat port (for macro lenses). On land a dome port acts like a window but, underwater, it behaves like a negative lens. It forms an apparent image of the subject for your camera to see (which appears closer) but which corrects for refraction. The apparent object distance varies according to the curvature of the dome, with smaller domes creating the greater distances. The laws of physics therefore dictate that bigger domes give sharper pictures!

Ports comprise of an optical element held in an aluminium tube which is physically attached to the housing usually by bayonet mount (and sealed by a user serviceable O-ring). For dome ports there is usually a shade to avoid flare and maintain contrast which may be removable to suit different lenses.

Port elements are made from acrylic or glass but, contrary to what you may think, acrylic is the best material to construct a port because it is easier to repair scratches, does not tend to mist up, and is cheaper. The best acrylic ports are injection moulded rather that vacuum formed.

As we said earlier, larger ports are preferable because larger ports give sharper pictures (and some also allow you to swap lenses without removing the camera from the housing). The optimum size for a dome is 8". This corrects for refraction above and below water so that half in/half out shots are possible. Domes smaller than 8" may require you to put a diopter lens on in order to focus properly (and this is a piece of optical trash you should avoid). A 6" dome is a good compromise.

Lens gears are toothed rings that mate up with external controls on a housing and are required to alter aperture, zoom, and manual focus settings on lenses. These gears either slip on for a tight push fit or are held in place by grub screws. Many lens gears are interchangeable so you don’t need to buy one for each lens but continual swapping results in visible wear and tear to your lens which will reduce its resale value. Much better to buy gears for each lens and leave them on permanently.

Leak Detectors
A good housing will not flood. However, once you introduce the human element into the equation you’re asking for trouble! User error means floods can happen at anytime. The vast majority of floods (99.9%) happen within the first three metres of water. In fact, you would be surprised to learn how many floods happen in the freshwater soak tank!

There is no substitute for diligence, but leak detectors (audible and visual alarms built in to the housing) can help avert a tragedy at times when you are distracted. Considering their cost, relative to a new camera, they are a good investment.

WHICH LENS?
Whether you opt for an underwater camera or housed camera you will also need the right lenses to make it work to full potential. In this area also, a great deal of confusion exists. The ‘standard’ lens for underwater photography is the 35mm - insofar as it approximates what you see. This is the lens usually supplied with non-SLR cameras - but your photographic opportunities would, however, be somewhat limited if the standard lens was the only focal length of lens available.

Indeed, there are lenses where the focal length is less than the diagonal i.e. wide angle, and lenses with a focal length greater i.e. telephoto. Underwater photography suits the extremes of subject sizes, either close and small (macro) or close and large (extreme wide angle). The most useful lenses are therefore wide angle or those having close focus (macro) facility.

Prime and supplementary lenses
Any lens attached directly to the camera body is known as a prime lens. The only disadvantage of the prime lens is that once on the camera, whether in a housing or on an amphibious camera, it cannot be removed during a dive (so you are stuck with looking for subjects of the appropriate size).

The 35mm standard lens is rather difficult to use. At the close distances our typical underwater subject tends to be at, it has limited coverage and is critical to focus. You do not usually buy a 35mm with a housed system but with non-SLR cameras it is worth having one because you can fit supplementary lenses to covert them into a wide angle, or close up, lens. Unfortunately, supplementary lenses are optically inferior to prime lenses, a point usually reflected in their price.

Supplementary lenses are additional elements that can be placed over a prime lens on a non-SLR U/W camera to alter focal length and angle of view. The big advantage of supplementary lenses on non-SLR cameras is that they can be removed underwater and you can therefore swap them during the dive to match the size of subject you discover.

Wide angle
Reducing the amount of water between the subject and the lens gives sharper detail, richer colours, and increased contrast. This is consequently one general principle which is important to photographic success underwater. It also explains why the wide angle is the underwater photographer’s favourite lens (because it allows the underwater photographer to get a good scale of reproduction at close distances).

Typically, wide angle lenses have an angle of view between 90 and 60 degrees. Wide angle lenses have an enormous depth of field (the zone in the picture that appears in focus) and so are virtually focus free, making them very easy to use and versatile. They are suited to most underwater subjects from wrecks to divers and, because they can focus down to six inches in some instances, they can be used for smaller subjects too.

The majority of wide-angle shots that you see in the diving magazines were shot on the 20mm lens in a housing (equivalent to 15mm Nikonos/16mm Sea & Sea). A wide-angle lens should be at the top of your shopping list, right after a strobe. Wide angle lenses do unfortunately suffer from distortions, particularly curvature of field, which is especially noticeable at the edges. On land this effect can be distracting, but it is not a disadvantage in most underwater applications as there are not many straight lines underwater to betray the distortions (except wrecks).

Fish-eye lenses are extreme wide angle lenses and can have an incredible angle of view of 180 degrees on the diagonal! Consequently they have all the advantages (and disadvantages) already mentioned for wide angle lenses - only more so! Some fish-eye lenses give a full format rectangular image, others only a circular area in centre frame.

Macro
Non-SLR and SLR systems go about macro photography in very different ways. SLR cameras use special lenses designed for close subjects whilst non-SLR systems use extension tubes and close-up supplementary lenses.

The macro lens for the SLR is designed for small, flat subjects close to the lens. The typical focal length is 50mm or 60mm but there are longer tele-macro lenses of 90mm to 105mm which are also useful. The most popular Nikon macro lens is the 60mm and this lens should be next on your shopping list after a wide angle lens. The depth of field with macro lenses is minimal (less than an inch) so this system requires reflex viewing to focus.

For Nikonos macro photography with the Nikonos V you use extension tubes. These are rings which fit between the prime lens and the camera body. With extension tubes, you do not require reflex viewing for focusing; the scale of reproduction is fixed, and the subject merely needs to be the correct distance from the lens in order to be in focus. This, and the angle of view of the lens, is shown by probes, wands, or framer attachments. Extension tubes do, however, have the disadvantage of dictating the subject size suitable to fill the frame and, additionally, are non-interchangeable underwater. The Sea & Sea range does not have a detachable prime lens and so uses close-up supplementary lenses for photography of small subjects.

Autofocus lenses for SLR’s
Most lenses for SLR cameras can be focused visually with minimum difficulty. However, there are some instances underwater where visual focusing can be slow, inaccurate, and tiring - such as with SLR macro photography. Autofocus (AF) lenses automatically focus for you and are available in most focal lengths and for most modern SLR’s. Autofocus is faster and more accurate than human reactions and it is not surprising that AF is now the norm.

Autofocus can be a boon underwater for most subjects, and especially useful if you wear glasses. However, some low contrast subjects can actually be frustrating to photograph with autofocus as the lens can continually seek, but does not lock on. However, in the majority of cases, Autofocus systems are so sensitive that they can work even when there is not enough light for the human eye to see (quite a common scenario underwater). An aiming light is a useful accessory to aid AF, it does not need to be strong, a pinprick of light is all you need!

Zoom lenses for SLR’s
Zoom lenses are lenses with a variable focal length and are becoming popular for underwater use in housings. They allow the photographer to remain in the same position whilst varying angle of view, or image size. There are few applications underwater where a zoom is a genuine advantage however, although zoom lenses are an alternative to a range of interchangeable lenses.

As previously mentioned, it is better to stay close to your subject underwater and, as there are no close focus zooms available that go from (say) 20mm wide angle to 50mm macro, you are still stuck with buying two lenses! There is another good reason why zoom lenses are not much use underwater. Wide angle lenses require dome ports and macro lenses require flat ports, so how do you change ports as you zoom through your focal length range? In reality you choose either one port or the other. It is generally accepted that 28mm is the widest zoom lens you should use behind a flat port, any wider you must use a dome (with a plus diopter corrective lens).

Which Strobe?
There can be no argument that the strobe is as important to underwater photography as the underwater camera. However, choosing an underwater strobe can be even more confusing than buying a camera as there are more manufacturers, and more models, to choose from.

Electronic flash is the most practical method to add light underwater and is provided by purpose built underwater electronic flashguns (often called Strobes).

We have tested all of the strobes commonly available in the UK and the results are shown in the data chart which you can download as part of our free U/W photo software. Just Click Here. This will download a genuine Windows Help file which you can browse to your heart's content. To find the data chart search the index of the help file for "Strobe power ratings" and click on the green text.

The data chart lists all the features to look for in an underwater strobe such as how it controls exposure, how powerful it is, and how that relates to it’s power source, and it’s size and weight. The first important feature to consider is the firing mode.

Firing mode
There are four possible firing modes that can be incorporated by underwater flash units: Manual, Automatic, TTL and Slave.

Manual units give a constant output each time they are fired, and so the correct exposure is achieved by the judgement of the photographer relating subject distance to aperture (not as difficult as it sounds). There may also be incorporated a number of different power settings to help the photographer control output.
Automatic strobes have remote sensors that read the light reflected from the subject and automatically quench flash output when correct exposure has been achieved. This method of determining exposure can economise on battery use as the flash need not fire at full power every time, but it is prone to error with non-standard subjects and may not, therefore, yield any more successful exposures than manual techniques in such circumstances.
TTL (Through The Lens) strobes are by far becoming the norm. They also respond to the light reflected from your subject, but this is measured by the camera, not by remote sensor, and also takes into account the aperture selected (and any filters). It is therefore more accurate, more versatile, and less prone to errors.
Slave mode can be incorporated into any of the previously mentioned strobes. The term ‘slave’ denotes that the strobe can be triggered remotely, simply by being in proximity to another flash going off. Such units are useful to augment your main strobe without the necessity of a connecting lead to your main camera. Usually slave mode is at full output so exposure is again determined by flash to subject distance.
Power ratings
The next feature important to your strobe choice is how powerful it is. The power of any particular strobe is expressed as the Guide Number. This number corresponds to the F-stop (aperture setting) required to get the correct exposure at a particular distance, and with a particular film speed. The standard adopted by most manufacturers brochures is the land guide number (which cannot be used for U/W calculations) and is in metres with 100 ISO speed, and is the one used on our table.

To determine the accuracy of the manufacturers stated guide numbers for our data chart, we measured the output of all the strobes tested on a Minolta Flash meter IV which has a known accuracy of one tenth of a stop (far more accurate than the shutter of your camera!). You may not be surprised to see discrepancies between claimed, and actual, guide numbers that we discovered on our test!

Power supplies
Underwater photography requires a lot of light and fast recycle times, which dictates efficient power supplies. It is not necessary to know exactly how the electronics work in a strobe in order to use one, but it is useful to understand the idiosyncrasies of the batteries you put in it! This is especially true when buying a strobe as the number, and size, of battery cells a particular strobe takes will determine its performance. The ideal battery should allow the unit to be able to deliver many firings and recycle quickly. The three main types of battery used in strobes are (1) Alkalines and (2) Nickel-Cadmium (Ni-Cad) (3) Nickel Metal Hydride (Ni-Mh).

Alkalines are extremely efficient in that they give many firings and do not fail abruptly, but have the disadvantage of their limited life-span which makes them costly. The travelling underwater photographer needs a power source that will shoot a roll of film (at least) twice a day for every day of a two week holiday. You would need to carry 14 packs of Alkalines for such a trip (one for every day of your holiday with most strobes). Apart from the inconvenience of carrying that little lot about with you, just think also of the effect on the environment of producing those 14 packs of Alkalines!

Ni-cads can be recharged hundreds of times and are therefore the most cost effective power supply. They are ideal for the travelling photographer as you only need to take two sets with you (one for the flash and one to keep on charge). Ni-Cads offer faster recycling times, but less firings, and fail more abruptly (usually without warning and usually in mid roll!). They normally require 14 hour charging times and can develop a ‘memory’. You must discharge them fully before recharging otherwise they ‘remember’ and will only take a part charge next time.

Nickel Metal Hydride are the latest thing in battery technology. Originally devised as power sources for laptop computers Ni-Mh batteries are also re-chargeable. They deliver more power, quicker, and with no memory problems. They can also accept a charge in an hour!

Most strobes shown on our chart have removable batteries and can use either Alkaline or Ni-Cads. Some strobes however, incorporate integral Ni-cads which cannot be removed but which usually are industrial grade and of high capacity. Some models boast sealed battery compartments, this is a useful feature in the event of a flood as the internal electronics are protected.

TIP! Do not use rechargeable batteries in your camera. Use standard, Alkaline (or lithium) only. The voltage is lower, and this can throw off your meter!

Firing and recycling
It is obviously important that you get a reasonable number of firings per set of batteries from your strobe. The number and size of cells is a rough guide, however, in order to determine how many flashes a strobe will give, the efficiency of the circuitry is the main factor.

It is also important that your strobe recycles quickly if you don’t want to miss any photographic opportunities, especially with action subjects. Even with static subjects, you need to work quickly because the silt will billow up to create backscatter very quickly if you settle in one spot. Like guide numbers, claimed recycle times and stated number of firings should be taken with a pinch of salt.

Coverage
Flash coverage is another factor to consider when purchasing a strobe. The coverage of the flash should match the coverage of your widest lens otherwise your shots end up lit very unevenly. This is probably the commonest mistake to ruin beginner’s shots.

Most strobes cover either a standard or wide angle lens. If you buy a strobe to match your widest lens then you will cover all eventualities, but you shouldn’t be put off a buying a narrow beam strobe if the price is right. Coverage can always be increased by the use of a diffuser to spread the light (at the expense of power output - another reason to over-buy on power).

Flash Construction
Small is beautiful for any diving equipment if you travel extensively, as airline baggage weight allowances were not designed for divers or diving photographers! Fortunately, most flash manufacturers have compact units and lightweight designs are now the norm. However, chargers often weigh as much as the strobe so this is also a consideration. It is a good idea to only carry one charger so that, if you carry a torch for example, you should ensure that you can use the same charger with it as with your strobe.

Flash Connectors
The connectors on the flash that you intend to purchase should obviously match those on the camera that it will be plugged into. There is no standard for connectors on underwater strobes, although the five pin Nikonos V plug and socket is almost universal for TTL strobes. Some types of lead can have connectors which can be unplugged underwater. This is an advantage should you wish to take two cameras but only one flash (or two strobes and one camera).

Flash Arms
You will probably buy a flash arm when you buy a strobe and here lies another minefield. How your strobe is physically attached to your camera can also make, or break, it’s performance. The traditional design is a straight bar which, although functional, is fairly limiting. It is a great advantage to be able to get your strobe off camera and so disconnect systems are to be preferred.

As in the case with connecting leads, there is no standard mount for strobes and so most underwater photographers are forced to customise their favourite mounting arm to mate with their favourite strobe. The most popular design of flash arm is ball jointed. Designs that cannot be locked in position usually require constant attention in use and should be avoided. Ensure that the arm system you buy is compatible with your strobe and housing. Only one manufacturer (TLC) has a system with a high specification and can promise to connect any strobe to any flash.

Flash Extras
There are one or two other integral features to look for on a strobe. These include modelling lamps (built in torches which usually utilise the same batteries). They are useful to preview coverage but not very effective in daylight conditions. Audible status warning signals can be useful (if you can hear them through your hood!).

Choice of strobe
Final choice of strobe should not be made in isolation from the camera it is to be used with, nor subject matter it is to be used for, nor size of pocket that has to pay for it! For example, there is no point in paying extra for a TTL flash if you only have a manual camera, nor is there any point in buying a power flash if you only shoot macro.

Some people go for power strobes but, if you only ever dive in UK waters, a power strobe can be counter productive. All you may succeed in doing with a power strobe is lighting up more suspended particles in the water, and thus get more backscatter. Lesser powered units are therefore to be favoured in lower visibility, so there is some case for buying a smaller strobe if you only dive in UK waters.

Conversely, there is justification for buying a larger powered strobe than you need if the coverage is not sufficient for your widest lens (because you will lose output when you put a diffuser on). Also, because shooting on less than full power shortens recycle times, it could be a good strategy to buy a more powerful strobe than you actually need to improve recycle times. The number of flashes per set of batteries is also correspondingly increased.

There is also a lot to be said for spreading your budget over two strobes rather than one. That way you always have a backup, or can simply use the second one to augment the power of the first. With a second strobe you can ‘fill in’ the shadows and this is a particularly popular set-up with the professional.

All the strobes on the market will do the job, but some will be more suited to your application, and pocket, than others!

FLASH HOUSINGS
It is now becoming popular to house a land flash for underwater photography. Land flashes offer the ultimate dedication with housed cameras and can therefore allow you to take advantage of all the advanced features available to your camera system.

Housing a land flash can also now give Canon and Minolta owners, who were previously put off housing their camera (by not having a TTL flash) the incentive to buy a housing. Nikon owners can experience features not available to underwater strobes, such as 3D Matrix metering Balanced Fill TTL Flash (now that’s a mouthful - it’s just a new style of TTL for ensuring flash exposure does not overpower the subject). There is also a feature on Nikon flashes called Monitor Pre Flash - which measures the reflectivity of the subject and then the camera adjusts exposure accordingly.

However, not all cameras can take advantage of these advanced features. For example Nikon owners should note that Pre Flash and Balanced Fill flash is only available to F90 (or later) cameras. There is, therefore, little point in buying a flash housing if your camera is not compatible with the system flash’s advanced features. For example, using a Nikon land strobe with an F801 camera gives no gains - you will only get standard TTL.

Similarly, some flash housings do not support the advanced functions. Tubular designs of flash housing offer least functionality (because the flash must be opened out straight - a position which is reserved for land bounce flash and so automatically disables Pre Flash and Balanced Fill flash. With tubular designed flash housings you don’t get any of the advantages, but you do get the disadvantages; poor recycle times, lack of power (compared to even the most basic underwater strobe), less shots per set of batteries, awkward handling etc.

Only clam shell, cast aluminium housings allow the (Cobra head) flash to remain in the bent over position with no loss of functionality. Such housings are more expensive (as much work goes into them as a camera housing) and more cumbersome.

Whichever flash housing you choose, it should (as a minimum) allow you to switch it on (and off for natural light shots) underwater.