Life through a lens
The biggest difference between an SLR and a compact is that you have the option to look directly down the lens... Because of this you can't work from a moving LCD display in the same way. Large bright displays have played a big part in making digital cameras popular underwater so it can seem a bit daunting to give it up.
You may have seen that lots of Digital SLRs now offer 'Live View' and hoped that it would mean they work like compacts underwater. As of now there are very few Digital SLRs which actually do. Because many advantages of an SLR rely on that direct view of the scene, they cannot easy emulate a compact. This makes most live view options quite clunky – literally. They have to flip their mirrors up and down to focus and take pictures. That's not to say you can't use live view - it can be very handy in difficult spots. On the surface live view is sometimes suggested for macro work, but underwater it is very difficult to work that way, as you won't be using a tripod. It's much more useful for wide angle shooting where you may want to look around the scene from behind the camera or take a high or low viewpoint which is difficult to get your body into position for.
The direct view through the lens is actually a very rewarding and effective way to frame your subjects – no surprise to keen photographers of course. Being able to see exactly what will be in shot allows better composition – although there are none of the exposure clues you'd get with an LCD view. You should be thinking, not just pressing buttons :-)
Any port in a storm
If you are moving from a compact to a Digital SLR, the issue of ports may be new to you. SLR lenses are so varied that they need a choice of different front ports to accommodate them – the demands of ultra wideangle are very different from those of macro. There are two characteristics which determine the right port for a lens; field of view and physical length. Luckily, there's some latitude, but you will probably need several ports unless you are interested in only one genre of photography.
Macro lenses (and any lenses longer than 28mm equivalent) work best behind a flat port. This preserves the benefit of the 25% magnification that you see yourself when using a mask underwater. Light is refracted as it crosses the flat glass barrier between water and air – so it gets you closer to your subject. The front glass should be large enough not to vignette (have a dark surround) as the lens moves but can still be quite small for powerful macro lenses.
Wide angle lenses (wider than 28mm equivalent) ideally require a dome port. There's no point using an ultra wide lens behind a flat port – it will suffer from chromatic aberration (rainbow streaking where light enters at an extreme angle) and vignette behind anything but the most enormous window. Dome ports provide a perpendicular air/water interface to eliminate the magnification of a flat port – so your view is wider. They also surround the lens so they should not vignette. Dome ports are bulbous, large, expensive and vulnerable to damage. The best are made of glass; they resist scratches and are optically superior. Acrylic domes are cheaper, but scratch very easily. While compacts can approach SLR macro performance, the availability of dome ports and ultra wide angle lenses is one major reason to move to an SLR.
As you can guess, there's a middle ground where you could try either a flat or dome port, but why compromise when you've bought the SLR, the underwater housing and the dream holiday? Thus few people use kit or general purpose lenses underwater. They are a compromise to house and often not the best at any particular job. There are rare lenses which can work this way; the Olympus 12-60mm is so versatile it can do both wide and near macro, but they are few and far between – and difficult to house as they can extend a lot!
The two genres
The choice of lenses for SLRs can be mind (and wallet) numbing but you shouldn't be limited by what comes in the box. Super close up and ultra wide angle options are there for the picking,
Shooting macro can be a bit nerdy, it's a bit like visiting a stately home and just taking pictures of doorknobs. There are some stunning little things about, but it is quite a performance finding them, photographing them and then explaining to incredulous friends and victims what the hell they are looking at. I love it. Whereas all compacts can be put into macro mode, normal SLR lenses don't focus well close up. SLRs have dedicated macro lenses. These are prime lenses, single focal length lenses, designed specifically for close up focus. Macro lenses are superb tools, generally offering 2-4x the magnification of a compact's macro mode. As they are often the equivalent of 90-100mm, they also let you shoot from further away - so you can snap nervous animals. Shooting from a distance can mean your wobbles will send the lens focusing off into the distance either side of your subject and macro lenses tend to have long, slow travel – for precision – so it can be frustrating.
The combined properties of SLRs and macro lenses combine to give a very limited depth of field. They can give you a paper thin sliver of the subject in focus. If you thought getting small things in focus was hard with a compact you may be surprised to find that with an SLR you might have trouble getting enough of a subject sharp to impress. You can stop down the aperture to get more of the subject sharp, but as each stop doubles the light you need for the same exposure, you will need a powerful or efficient strobe to cope. Long before you have as much depth of field as a compact, you will run into the diffraction limits of the lenses; the point where the overall photo becomes softer. This is another reason why you need larger strobes with an SLR than for a compact. Shallow depth of field is one aspect you have to grow to love.
When I approach a macro subject I have in mind how much depth of field I want, dependant on size and distance, and set the aperture accordingly; f13-16 for very close, f9-11 for things which are merely small, f5.6-8 for portraits of medium animals and f2-4 for fish at distance. This balances the need for accuracy, depth of field and strobe power. My Zuiko lenses are sharp wide open but I need to give myself a fair chance to get enough of my subject in focus! I use autofocus; it frees my hands for holding the camera steady. I don't change shutter speed much, I select faster speeds (1/500th to 1/2000th) to blacken ambient lit backgrounds or longer (1/30th to 250th) to allow more natural light in for a less studio look. Shutter speed is a very pure way to control light, as the TTL flash will maintain exposure. Aperture changes can be made too, but they treat all light equally, and alter the depth of field of course.
Wide open spaces
I still find wide angle photography a challenge, it's an artistic discipline and I'm not always up to it. Essentially, you are capturing a beautiful scene rather than creating a new one... so you have to work with the natural light much more sensitively, otherwise you will create something artificial. Another challenge is to engage the viewer with your focal point rather than just hope they will enjoy playing where's Wally in the background. Wide angle scenes work best with a significant subject, maybe a shipwreck in the distance, a diver at arm's length or an object close up – or perhaps all three! Some uniform coral reefs don't lend themselves to this and many cold water sites don't really offer the variety in a scene to play this game, but where there's a will there's a way. There is always something you can feature... often your buddy... and always a back drop, even if it is the dark of a looming hull in the North Sea.
Wide angle lenses also let you get closer to scenes or larger animals and still fit them in. I have been to Holland several times to watch cuttlefish breeding where the conditions can be very difficult. A wide angle lens can help by cutting the distance you need to be from your subject – reducing the amount of crud between you and it!
I am camera, hear me RAW
In case you haven't heard a RAW file is like a digital camera's negative, while a JPEG is more like a print. This means you can extract more from a RAW than a JPEG... but it will still be difficult to improve on a good JPEG. Although some compacts can take RAW photos, they tend to slow down so much that it's not much fun. Most SLRs can shoot RAW at the same speed as JPEG but the files are larger so even they will often slow after shooting a few in rapid succession. Large, fast memory cards are a must! I shoot RAW and JPEG simultaneously which eats cards at nearly 20MB per shot. I do this because JPEGs are quick and easy to exchange straight away, whilst RAW files need to be developed and not every program can handle them. This means I need to carry plenty of cards and backup storage to cope.
The beauty of RAW files for underwater use is that as they are taken without a white balance setting, so a better one can be chosen afterwards... RAW files can do this because they record the scene in greater depth than JPEG, which means you can often recover detail from highlights and shadows. Don't rely on this trick, it's much better to take good photos than hope you can pull the cat out of the bag later, but RAW files are certainly a better start for fine adjustments. Some people believe this removes the need to set a realistic white balance in the first place and even means they won't need a strobe. Those people aren't the ones who will be taking colourful macro shots or natural looking scenery. The white balance setting affects exposure, so if it is way off you will unduly limit your scope for correction.
Strobes of many colours
Just to be different, divers prefer to call their flash guns strobes. That aside they are pretty much identical... aside from the tricky issue of connecting them to cameras. The difficulty of making reliable connections underwater has kept the underwater flash several steps behind its surface counterparts. The most commonly used connection dates back to the '60s. Based on the system which was used by the Nikonos camera – a system Nikon developed with and then bought from Jacques Cousteau. Things have changed a lot since then and while there have been other systems made by specialist companies, without the resources of a mass market, the Nikonos connection remains popular.
If you are choosing a set, this doesn't mean you have to buy Nikon – it isn't always any benefit - bizarrely even some people with housed Nikon's still have to use manual mode because their chosen housing doesn't carry all the connections through to their Nikonos connected strobes. Nowadays, there are plenty of ways to make various strobes work with most cameras. At the heart of the system is the principle that as long as you can trigger a strobe, you can adjust the camera to cope. Triggering is easy – precise control is hard. True TTL (Through The Lens) flash control is rare underwater and it is often compromised.
It is the fine control, now a given on land, which is unusual underwater. If you were buying a land flash, you'd choose one which was dedicated to your camera, but that isn't so easy underwater. Housed land strobes are one way to get control, but they can be very bulky. Olympus uniquely make their own dedicated underwater strobe, but so far everyone else has to make do with third party support. Adding to the confusion are some housings which translate perfectly good camera TTL control into their own protocols to tie you to their own strobes. Super powerful strobes are very specialised; venture carefully into that market, just as you would if choosing studio lighting.
Several manufacturers now make systems which are an interesting hybrid; TTL systems which are controlled optically. These vary in complication. Some just copy the camera flash – which can work well, but it does have limitations. The best use the camera flash to transmit control data to a strobe optically via fibres. These offer all the control of wired TTL with no cable to corrode. The first of these to appear underwater is the Olympus UFL-2. Read my Olympus UFL-2 review.
If this leaves you confused, join the club. There are systems which will translate all major camera TTL systems into signals that most common strobes understand and there are, at last, manufacturers who make a full system of their own. But where does that leave you? In the first place, I would put as much consideration into your lighting as your housing, the wrong choice can limit your options.
I'd suggest a few simple strobe rules which may help you;
1. The first strobe is the most important, a second can be triggered by the first as well as the camera.
2. Two strobes aren't always better, aside from the bulk, uniform light can flatten your subject
3. TTL isn't the be all and end all for wide angle but is very, very useful for macro
4. Strobe cables are the most unreliable part of a strobe system
5. Open optical triggering isn't foolproof – fibre connections are required
Choosing a strobe is the easy bit, actually using one is the most challenging part of many people's underwater experience. There's plenty to consider from an artistic standpoint as well as the persistent difficulty of maintaining wired connections underwater. It may be that the new fibre connected dedicated wireless systems are the heroes that finally save the world from complicated strobes.
SLR Round up
Our whistle stop tour has introduced you to some of the factors to consider when warming your wallet up ready to buy an underwater SLR rig. It's not to be taken lightly as, with luck, the kit you buy will accompany you on many dives and, like your dive gear, you'll want to have something that suits the way you dive as well as the way you take pictures. I was a compact user for a long time and felt I'd done pretty well, but using an SLR has opened up new options and really stretched my photography.
That's not to say it's all downhill and that improvement is guaranteed, plenty of people take a while to get used to the weight, task loading and potential complexity. Some don't. As with many hobbies, underwater photography rewards preparation and practise – having all the gear isn't quite enough! When you do 'take the plunge' don't expect immediate results... practise, practise, practise... then the pictures will come!
My final hot tip is to take lots of advice (mine included) with a pinch of salt. Most gurus have comparatively narrow experience and no matter how balanced someone trying to help thinks they are, they will rarely see the whole of your picture – try asking how many different cameras they regularly dive with.
Thanks to Caroline at Rainbow Divers Vietnam for her tropical modelling!