Written by Doug Perrine August 2017
After all the hyperbole in this blog about the difficulties of focusing on blackwater subjects, you may be forgiven if you have assumed that once you have mastered the “focus part” that perfect photo files will be swarming onto your hard drive like June bugs on a summer evening in Texas. AuContraire! (as we like to say in Lubbock). The second bugaboo, named Exposure, is about to bite your hiney like a Texas swamp mosquito swarm. OK, forgive me, I just returned from my old stomping grounds in the Lone Star State and the influence is obvious.
Again, the problem is that most of the things you are trying to record are mostly transparent. Light doesn’t reflect off them to allow you to focus, and it doesn’t reflect off them to expose an image on your sensor. The first part of the solution is more light. For this I use dual Ikelite DS161 strobes at point blank range, and it is barely enough. The second part is aiming. The old school solution to transparency is “backlighting.” True backlighting doesn’t work unless you have a way of blocking the light from shining directly into your lens, which is virtually impossible to arrange for scuba diving. So for underwater photography, by “backlighting” we mean pushing the strobes forward and turning them inward so that they light the subject from both sides, without shining into the lens. I use this method, and it works.
My dive buddies, Skinny and Chubby, both masters of blacro, use a completely different technique. They keep their strobes very close to the camera housing and pitch them outwards (bowlegged vs. my pigeon-toed), so that only the edge of the strobe beam lights the subject. That also works. Their results are similar to mine, with possibly less backscatter. The similarity is a function of the fact that we are both, in fact, finding ways to reflect light off the parts of the subject that will reflect it, while avoiding, as much as possible, lighting the particles between the lens and subject. True backlighting, in the sense of shining a light through a transparent subject into the lens, is just not practically achievable in most underwater photography applications.
To achieve a decent exposure, it is not enough to use powerful strobes. I also crank the ISO up as high as I can without getting unmanageable noise. In a modern Nikon camera, like the D500, this means ISO 800-1000. This allows me to use an aperture of f22 for most subjects, which hits the sweet spot of Nikon’s 60mm macro lens, with reasonable depth of field. At f25 and above diffraction compromises the resolution of the photo.
Chubby, who uses an older DSLR, with more noise per ISO, opts for lower ISO and a wider aperture. He sacrifices depth of field, but claims he likes the artistic effect of having only one part of the subject in focus. I have to admit, his pictures are pretty darn impressive.
A major challenge comes from the fact that the occasional nonconformist subject wanders in front of your lens. While all of their neighbors are sucking strobe light into a black vortex at the far end of the marine universe, these lanternfish, flying fish, and what-have-you reflect light back at the camera like a 1980s disco mirror ball. So you need a practical way to switch instantaneously from full strobe power to 1/32 or 1/64th power. Until recently, unless you were shooting Ikelite strobes with an Ikelite housing, this was a real problem. As a devotee of aluminum housings, and Nauticam housings in particular, I was left out of the TTL strobe auto exposure loop and was faced with a choice of reaching out to each of my dual strobes to turn the power down, or finding the ISO button on the housing and pressing it with one hand, while looking at the viewfinder display and turning a dial with the other hand. In either scenario, the subject was long gone by the time I had my exposure ready for it.
Ikelite came out with an external TTL controller that worked pretty well, but not with the original strobe circuitry in the D500 housing. The guys at Nauticam USA are always tinkering, and within months they came out with a new circuit board. That one did great TTL with my Inon strobes, but my Ikelite strobes didn’t work at all. In short order, however, they developed a circuit board that supports TTL with a variety of strobe makes including Ikelite. After two blacro dives with the new board I can truly say it is a game changer.
When I started doing blackwater photography with a Canon 5D MKII (a great camera for its time), I was really happy to get one “keeper” photo out of a dive. With the Nikon D800E, I was getting more like 5-10 keepers. I crossed a barrier with the D500, and went up to 20 or more keepers on some dives. But by combining the incredible low-light focusing ability of the D500 with powerful strobes and accurate TTL exposure I’ve jumped up to more than 50 photos jamming my hard drives after the last couple of dives. With a broad range of reflective to non-reflective subjects, the great majority of photos were perfectly exposed. Having said that, I should add the caveat that the TTL with Nauticam’s circuit board, just as with Ikelite’s external controller, seems to fall down a bit with subjects requiring full power. The circuitry seems to not want to do a full dump, often opting for a light under-exposure instead. By keeping the aperture dialed open enough that no more than 90% or so of the strobes’ power is required, pretty consistent results can be obtained, even when the subject covers most of the frame in one shot, and a tiny fraction of the frame in the next.
Marvels of modern electronics like the D500's low-light focusing system and Nauticam's TTL board can't take a great picture by themselves. But by freeing us to compose an image without needing 5 extra hands and an extra brain to follow focus and change exposure on the fly, these tools make it a whole lot easier to get good results in one of the most challenging realms of photography.