Having the best of the best underwater camera setup money can buy is not the key to getting great mandarinfish (Synchiropus splendidus) shots. It’s about using what you have and knowing how to use it.
On a DSLR or Mirrorless (full frame or APSC), the preferred lens is a 50 to 60mm Macro. For a Four Thirds, a 30 to 45mm macro should be all that you need as you can get quite close. Marco lenses with a longer focal length will do the job, but you won’t have as much depth of field even at F/32.
In this scenario, my own camera settings are often set as follows:
Shutter Speed: 1/125 to 1/200 sec
Aperture: F/19 to F/22
ISO: Start at 200. If your strobes struggle a little to match the selected F-stop, bump the ISO to 400.
Strobe Power: ¾ power is a good target setting as you will need a quick recycle speed.
Back Focus: if your housing has a back focus button or lever, set your camera to use it. This way, as you are following the fish through the viewfinder, keep your forefinger on the shutter, with your thumb on the back focus button to independently follow the fish to keep them in focus.
If the auto focus of your system does not have the greatest ability to quickly follow focus on even slow-moving subjects in low light, preset the focus on something the size of your small finger that comfortably fits within the frame. Doing so, you would only need to move slightly in or out to keep something like a mandarinfish in focus. Yes, this is old school, but this is how it was done even before autofocus.
Before the sun sets, you should scope out the best spot to settle down and minimalize your movements to eliminate stirring up the bottom and/or frightening the fish. Mandarinfish are typically shy.
From there, keep a look out for the largest, fattest mandarinfish you can find and follow where it goes.
At this point, lighting is key. Like most small fish that are highly active in the dusk to dark hours of night Mandarinfish Do-Not-Like having a white light shined on them. Using modeling lights with only white light function will more than likely keep the little fish down in the coral dampening their natural behavior.
To be far less obtrusive, using a modeling light with a Red mode, or at the very least one that can be fitted with a red filter to the front, is most desirable as the mandarinfish will take far less notice of it allowing you to more effectively see and follow their movements.
If you have succeeded in finding the right place to be before the drama starts to play out, you should not need to move from that spot as the mandarinfish courting behaviors will tend to work in a more vertical direction. Knowing that in advance helps you better track the fish through the viewer.
Keep in mind that when mandarinfish are about to mate they will rise upwards a foot or more above the coral. To catch the peak of action you need to be patient and wait for them to reach the zenith of their ascent. By this point they are often too connected to break apart before mating has actually occurred. That is the moment to start taking the shot, as the release of their eggs and sperm in unison will last no longer than 2 to 3 seconds. From there, the ending is marked by their sudden retreat back into the coral.
Happy shooting.
