Pygmy seahorses are called that for a good reasonthey are very, very small. The largest ones are less than 31/44 tall and most are no more than half an inch high. I have had the pleasure of spending many hours diving with these amazing animals, and I always photograph them at greater than life-size. I often use a +3 diopter on a 105mm lens to produce a 1.4x image (40 percent enlargement). At this magnification, the picture shows how well the seahorse blends with its environment.
Shots like this one, where the animal fills the frame, require even more magnification. A 2x teleconverter, placed between the lens and the camera body, will yield images that are twice life-size. An even larger image is possible by placing the +3 diopter on the lens. The final result is an image that is 2.8 times life-size. At this magnification you see details in the body that simply are not visible at lower magnifications.
When a pygmy seahorse has its back turned out, as it often does, it is very well camouflaged. The first time I saw a seafan with pygmy seahorses on it, I searched for 15 minutes before the dive guide began pointing out the 28 tiny seahorses that lived there. Unless you know what you are looking for, they are practically invisible which is why they werent discovered until very recently. A head-on shot like this one shows up much better, but required untold patience on my part and lots of luck.
This shot was taken with a Nikon F4, 105 micro lens, 2x teleconverter, 4T diopter, dual Ikelite 200 strobes, Ultralight strobe arms, and Nexus housing. The lens is focused manually and the exposure is via TTL flash exposure, with the camera in manual mode. The picture was taken in Lembeh Strait, North Sulawesi, Indonesia.