The fun of shooting with ambient light
Shooting with natural - ambient or available- underwater light can be a challenge, if not 'cool'. Strobes are the widely accepted tool to cope with conditions like color absorption and light diffused by multiple particles drifting in the water column. But when not carefully balanced with natural light, they lead to unnatural lightings of your UW target. Strobe shooters may also lose their sensitivity to catch the unique atmosphere of the underwater landscape and light fall, as you see or experience it through your eyes and diving mask. For example, when drifting over a lovely Red Sea coral garden, or the white and sunlit sandy Bahamian sea floor. With natural light, you depend on shutter speed, aperture, ISO and the light conditions underwater. You won’t have your strobes to add color to an object close to your lenses, creating a nice contrast with the blue natural background. Which means that your range of suitable targets and light conditions is very limited.
As said, natural light UW photography is not easy, because of the conditions underwater work against the principles of photography. Best conditions are plenty of sunlight and shallow depth (say not more than 30 feet). In short; keep the path that light travels (vertically as well as horizontally) as short as possible. There are two reasons why underwater photography without strobes often leads to poor and disappointing results. One being longer shutter speeds. Longer shutter speeds can be useful to bring in more light from the blue background while using the strobes to light up a colorful closely focused (often nonmoving) target. But without strobes, longer shutter speeds will cause a blur of a moving target. A second reason is that the underwater color cast drops sharply with greater depth or a greater distance to the object, causing a monochrome and dull UW landscape. Light diffusion is another factor. Taken together these factors will produce pictures with poor contrast and bleak colors, especially when your target is further than 1 meter away.
A way around to restore colors is to use a red filter (e.g. the ‘Magic’ filter). The filter also requires sunny days, and with the sunlight coming from behind your back. The effects of filters are most rewarding when shooting large (often static) objects like wrecks, at a distance when strobes would not be of any use. So stay as shallow and close to the object as possible. With a fish-eye lens, you can get pretty close to the wreck. The stern of the Ghiannis D wreck in the Red Sea, for example, has become a classical ‘template’ for wide-angle shooters (see for another example the insert with the Abu Nuhas wreck in the Northern Red Sea). When using the filter, you will need to adjust your white balance manually, preferably at the same depth where you intend to do the shooting. One believes that it gives better results than adjusting the image after shooting with Photoshop. Shooting very big sea mammals like whales, moving slowly at shallow depths, is another example of a condition where a fisheye lens is a must, and there is no direct need for strobes.
Some ambient light pictures I took last month during my visit to the Bahamas may serve to illustrate my point. I used the Olympus F1.8, 8mm fisheye lens without the strobes, mounted with a Zen extension ring on the EPL5 4/3 Pen camera in the EPL10 housing. I normally use this rig to back up my bigger Nikon D7200 with strobes combo. Unfortunately, there is no way of attaching the magic filter to the rear of the Olympus lens, like with the Lumix Panasonic 8mm lens*. I used automatic white balance adjustment, with slight corrections of the images in the RAW Adobe Photoshop CS5 mode.
On that particular day on Tiger Beach, we did a shallow dive (12 feet) with plenty of sun and good viz. I wanted to get a sharp picture with enough color and contrast of sharks (in particular of their head) while they moved slowly at a distance of maximal 1 meter. I used normal apertures (f11-f13) and shutter speeds (1/100 to 1/125). I felt rather happy with the result.