Underwater photography - Capturing the Thistlegorm

A couple of years ago, DIVE asked readers to vote for the best dive site in the world. It was no surprise that the HMS Thistlegorm romped home in first place, for this wreck certainly occupies a special place in the hearts of British divers. So this month, I am tackling the tricky subject of taking a photograph that captures the essence of diving among all that hulking metal and history in Sha’ab Ali.

Photo: Alex Mustard

Size matters when it comes to wreck photography, which means strapping on our widest lens and going for the big shots, showing as much recognisable ship as the visibility allows. Artists always paint wrecks this way, with a whole ship sitting on the sea bed amid the blue. This is how people imagine wrecks, so photos taken in this style are naturally appealing. If the wreck is shorter than the viz, we can shoot the whole thing. For bigger ships, however, we must focus our efforts on large recognisable features, such as the bow, stern, bridge and propellers. When possible, add a diver to the frame to convey a sense of both exploration and scale.

Shooting such expanses of superstructure means that the subject will usually be too large to illuminate with strobes, so turn them off and work with the ambient light. We have three choices: leave the images with a blue or green cast for the maximum atmosphere, convert them to black and white for the most contrast, or use manual white balance and filters to bring out the colours of the wreck. In low visibility, we can inject the most impact by shooting into the sun, boosting the contrast and showing the wreckage as a silhouette. But when the water is clear, shoot with the light coming over your shoulder and illuminating the details of the structure.

The Thistlegorm offers a very different challenge because the visual story of this wreck is not really the ship, but the contents of its holds. An underwater photo of a bike or a truck simply shouts Thistlegorm, and this is what we should focus on. However, shooting in the holds is a unique challenge and getting really strong images is not straightforward.

The dark is the obvious problem, which means that, unlike with most wreck photography, we have to use a flash. Since our foreground illumination comes entirely from our strobes, aiming them correctly is crucial and makes the difference between average snaps and standout shots. The common mistake is to position our strobes in the Thistlegorm just as we would on the reef – with the strobes either side of the lens. This is not the best lighting solution because, in the darkness, the subjects will accentuate the fall-off of light as they extend back into the frame. Many shots you see taken in the holds show this: the front of the subject is lit, but the light fades away rapidly.

The solution is to push our strobes out and, most importantly, up on long arms to create a pool of illumination in front of the camera by top-lighting the scene. This gives a more even lighting with a more gradual fall-off of light away from the camera.

Next, to give the image more depth, we have to lengthen the exposure to burn in some ambient light in the background. As we’re tucked away deep in the ship, this usually means a long exposure, but since there is no ambient light on the subject, you will be surprised how long you can push the exposure and still get a sharp image courtesy of the flash. This photo, for example, was taken over one fifth of a second. Of course, newer cameras can perform miracles at higher ISOs, so we can also bump the ISO up and reduce the exposure times accordingly.

Another problem in the darkness is focusing, and if we use a torch to help, the beam will show up in the image because of the long exposure (or high ISO). As soon as I get down to the Thistlegorm, I focus on the winches near the bow and then lock it in manual for the rest of the dive. This guarantees that every photo in the dark holds is sharp. It’s important to set the focus in the water, otherwise it will not account for the optical effect of the dome port.

The final problem of shooting inside the wreck is straight edges. The best lens to open up space underwater is the widest – the fisheye. But fisheyes achieve their ultra-wide coverage at a cost: they introduce barrel distortion. This is not an issue on the reef, but you have to be much more careful with man-made subjects – and particularly inside man-made subjects. The bikes, trucks, walls, floor and ceiling will all reveal this distortion. It’s unavoidable, but we can minimise the effect by careful framing, keeping important elements away from the corners of the frame, where the distortion is strongest, as I have done here with the bike and diver. I am happy with the result.

These days, however, we don’t have to stop there – we can use computer software to correct fisheye distortion. I have not done it here, but visit the PhotoPro forum at www.divemagazine.co.uk to compare the original image with a corrected version. I look forward to hearing which you prefer.

IMAGE DATA
Thistlegorm Bike. Nikon D2X SLR. Subal housing. Tokina 10–17mm fisheye @ 10mm. Long exposure 1/5 at f8. 2 x Subtronic Alpha strobes 1/4 power