Digital SLRs: flexibility under water?

Many professional underwater photographers have switched to a digital SLR (Single Lens Reflex) camera for some time now. And these days many hobby photographers also own such cameras, but for them choosing between their SLR or compact camera for underwater use is not an easy choice.

An SLR is a so called system camera: a separate body of considerable size, extensiable with a wide variation of lenses for wide angle, tele and macro photography as well as powerful flashes.

It is exactly this flexibility that allows an photographer to combine the equipment for the best results in a particular situation, making an SLR the prefered choice for many photographers.

But when such a camera is taken under water this flexibility will bring along some important consequences. This article deals with a number of considerations, drawbacks and benefits of taking a DSLR under water, and compares it with a digital compact camera.

Underwater Housings for Digital SLRs

The first thing noticed is the underwater housing for the SLR: usually it is quite large in size and is manufactured using aluminum, stainless steel and other sturdy materials, which can cause the weight to be several kilos.

Simply taking it in the hand luggage is thus not an easy task.

On the other hand, this kind of housing is much better equipped for the demands of the advanced underwater photographer: one or two strobe connectors, big handles and buttons, and multiple connections for arms and accessories are usually included. A maximum depth rating of 60 to 100 meters (60 to 350 feet) is also not uncommon, and a leak sensor may be built in if the housing's material blocks the view on the inside.

Lenses and Ports

The choice in lenses for the SLR also bring along special requirements. A housing for a compact camera is designed especially for the model and with the zoom lens in mind. An SLR housing requires attaching special ports that fit a certain lens.

Usually these underwater housings are equipped with a port for the default kit lens of the DSLR. Not all manufacturers provide a suitable port for every lens, so it is important to check whether the housing support the favorite lenses.

The type of port must also match the capabilities of the lens. A flat port has a flat glass window that reduces the viewing angle due to refraction (the change in direction of light as it passes from water to air, just like a diver experiences looking through his mask), which results in an enlarged image. Flat ports are therefore very suitable for standard and macro lenses. This type of port can also be used for zoom lenses, but not all ports allow operation of the zoom.

For wide angle photography (focal length of 28mm or smaller) the reduction in viewing angle is not desirable en thus require a dome port. This type of port has glass shaped like a hemisphere, and reduces or cancel out the refraction.

Not all lenses are capable of focusing behind a dome port, in which case a close-up adapter on the lens is required.

Flashing Digitally

While the internal flash of a compact camera can in most cases be used in their underwater housings, this is not the case with SLR housings due to the materials used. So unless the photographer can deal with the limited light and color under water, an external strobe is a must-have.

Slave strobes can not be used as these are triggered by watching for the camera's internal flash, thus the choice is limited to models that can synchronize manually or TTL ("through-the-lens") over a cable connection.

Luckily most SLR underwater casings feature one or more strobe connectors that are attached to the camera's hot-shoe on the inside, as well as a choice of sync cables for various connector types.

Not all underwater strobes support digital TTL (check out the digital underwater strobe page for more on digital flash protocols), so a photographer who requires TTL may need to look at the special flash housings that enable underwater use of popular "surface flashes" like the Nikon SB-800 and Canon Speedlite 580EX. Some housings even have built-in circuitry to convert the camera's digital TTL to a non-digital or compatible protocol thus allowing use of non-digital strobes.

Together with the excellent freedom of settings on an SLR, there are many combinations of strobes possible for successful underwater lighting.

Difference in Photographing

Photographing with an SLR or compact camera has some fundamental differences that are in many cases not even noticed on the surface, but can become quite important when shooting under water.

One of the consequences of the SLR principle is that the LCD screen can not be used as a preview (at this moment only the Olympus E-330 does offer this feature). This means that the viewfinder should always be used for composition, something that is not always that easy when wearing a diving mask. Shooting movies is also not possible.

The time and effort for assembling and preparing the housing, camera lens and port, make that the underwater photographer using an SLR has to choose the configuration considerable time before a dive. This limits the flexibility: the fish-eye lens and dome port chosen for a planned wreck dive may be useless if the dive is diverted at the last moment to a reef dive with lots of nudibranchs.

On the other hand there are also many benefits. An SLR has a larger CCD/CMOD sensor and better lenses that can still deliver correctly lit photos in darker conditions, and it can keep image noise to a minimum even at higher ISO values. The special RAW formats further extend the possibilities to correct a photo during post processing (also read the RAW or JPG? article).

Battery life is, mainly due to the limited use of the LCD and internal flash, incredibly long. It makes that an average digital SLR can take somewhere from 500 to 1000 photos on a full battery, and only takes less than a second between shots.

An SLR is designed with manual setting in mind, and that is also a benefit under water. While a compact camera provides many settings through a menu only, an SLR has many buttons and dials that allow the photographer to control the major settings directly.

Summary

It should be clear that going for a DSLR for underwater photography requires the necessary study and orientation on the composition of the camera, housing and accessories. It should be taken into account that the increased quality may imply a decrease in flexibility compared to a compact camera.

Of course, the choice also results in a quite a price tag: an underwater housing including standard port will easily cost more than a 1000 Euro/$ 1000USD, and additional expenses such as ports, arm, strobe and insurance(!) will further increase the price.

Even if money is no problem, it still is necessary to consider the benefits and drawbacks of an underwater DSLR and weigh these against the expected usage and interest in (underwater) photography.

More useful tips can be found in the tips and tricks for digital underwater photography section.

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