Tips For Photographing Mandarin Fish
Mandarin fish (Synchiropus splendidus) are quite possibly the most colorful fish that you will find in the ocean. They are a member of the dragonet family, and are native to the Pacific Ocean. They are a common subject for underwater photographers, and knowing how to photograph them will help you in your quest to get the perfect Mandarin fish image.
First of all, you should know that these little fish are not easy to find. During daylight hours, they tend tend hide in piles of dead coral. The easiest time to find them is around dusk, and you'll want to be in the water when the sun is setting.
Some dive resorts will have a "Mandarin dive" at sunset, but dive operators in the area will limit the number of people on the dive site, so your resort may not do these dives everyday. I've had the best luck photographing Mandarin fish in the Lembeh Strait, North Sulawesi, Indonesia. Honestly, as the saying goes, it's like shooting fish in a barrel, pun intended. There's 2, maybe 3 sites at Lembeh, and most resorts there are able to do a Mandarin at least every other day.
My tip: since the Mandarin dives are at sunset, you won't have a lot of time after the afternoon dive to charge batteries, change memory cars etc, so as soon as you get back from the afternoon dive, get your batteries on the charger ASAP.
The Mandarin fish tend to congregate in and around piles of dead coral. When the sun starts to sets you will begin to see them swimming in the coral, but while you may get excited and want to start shooting right away, you will want to resist this urge and save your strobe batteries for when the real show starts.
My tip: Use a focusing/modeling light that emits red light. Some people say that the Mandarin fish don't like white light and will avoid it, while the red light doesn't seem to bother them. I'm not sure if this is 100% true, but I've found that it works for me.
The male and female Mandarin fish will soon begin to appear and sort of check each other out. This is a great chance to photograph the males with their fins all spread out while showing off to the females. Their movement at this time is pretty erratic. They will swim around quickly, then tend to hover in one spot. You just have to be patient and wait for them to stop. The other challenging thing at this time is that they are still sort of hiding in the coral rubble. Try to find a spot where there are openings in the coral so that they won't be hidden from view.
GEAR AND SETTINGS
Mandarin fish are pretty small, although the ones I saw in the Lembeh Strait were pretty big, and are usually only a few inches in length. They're maybe the size of a bottle of nail polish, so while they are small, they aren't super macro. That being said I would recommend a 50mm macro lens on a crop sensor camera, and either a 50mm or 100mm macro on a full frame. The challenge when zoomed in too tight on them, is that you can lose sight of them when looking through the lens when they start moving around. Shutter speed should be the fastest that can sync with your strobes. I shoot with Canon, so for me that's 1/200. Your aperture will vary according to how much light you need with your ISO and the 1/200 shutter speed, but don't shoot too wide open (low aperture f stop) because your depth of field will be narrow, and when these little guys are moving, you may not always be able to lock focus on their eye. Speaking of focus, AI servo helps because it will track the subject as it moves after locking focus. I position my strobes near the end of mu lens barrel, and have the pointing slightly outward. Get as close as you can because there will be lots of particulates in the water, and you'll want to minimize backscatter. As I said earlier, I use a red light for focusing, and you will definitely need a focus light.
Soon enough, the Mandarin fish will begin to pair up for mating, and this will be the best chance to get you image. The males and females will come together, and you think they will pair up, only to have them swim away. Don't worry, it will happen. After a few attempts the males and females will connect and the pair will swim together vertically in the water column. That's when you get your shot, because they are so focused on the task at hand, that they seem oblivious to everything else. This is when you can get close to them for a good shot, but also, at this time they are away from the coral rubble so the background of your image is less distracting, and can often just be black. Although very difficult, you can try to use a snoot on your strobe to just light the fish. I'd recommend getting a few images with full strobes before trying this, because using a snoot on a fast moving small fish is quite difficult.