Underwater Video Lights 101

DSIVIERO-2365Not all lights are created equal, video lights make this point real clear. Lumen output, beam pattern and beam angle are by far your biggest variables, but let’s not forget size and weight. Dragging a heavy camera rig around underwater can be a major pain, and don’t even get me started on commercial air travel.

Beam Angle & Pattern

Let’s talk beam angle first as this is critical. You need a wide enough beam to cover the Field of View (FOV) of your lens. Underwater video typically uses wide lenses, commonly 100-130° in water. A default GoPro setup has a diagonal in-water FOV of 88° (reduce the native 133° FOV by 30% due to flat lens in water), meaning that a single light head with a 100° beam (in water) should give you ample to light the whole area being filmed.

Dome lenses are used on serious setups to maintain a lens’ native (or in air) FOV underwater. With wider lenses in water, say 110°, what this means is you’ll usually need two light heads to light what you’re filming. If using only a single light, you’ll have a lit circle with dark edges. Two lights will usually overlap; provide an increased lighting for the center and making beam placement forgiving.

Whether using one or two lights (that choice is yours), what’s critical is a matte even beam pattern. Hot spots, rings, banding or other artefacts cause distraction and you simply don’t want them. LED technology tends to excel in this area, though edges can be hard in dark environments without diffusers.

Lumen Output

Regardless of your tech (e.g. LED, HID, HMI, Halogen), you need good light output – measured in lumens(lm). Watch out though, a 120° wide 4000lm light will be equal in brightness to a 1000lm 60° one. The intensity of the beam is halved twice given that twice the lumens are spread out over twice the area. Keep this in mind when comparing light A with B!

How many lumens do I need?  Well it depends on your application. Below is a rough outline of what you’ll need as minimum for various setups.

  • GoPro Setup: 1 x 100° 4000lm+ light; or 2 x 60° 1000lm+ lights
  • Camcorder (Dedicated): 2 x 60° 4000lm+ lights; 2 x 100° 2000lm+ lights (preferred)
  • DSLR Video: 2 x 100° 4000lm+ lights (required for wider lenses)

Can you use your primary light as a video light?

For serious stuff, no. You can use it to light what’s in front of the camera, but you’ll get some serious hot spots as the tighter beams of a primary light mess with the cameras exposure capabilities. With a GoPro for example, you’ll either get a well-lit subject surrounded by black, or a blasted subject surrounded by well-lit. Again, for home videos do what you like – something to show your family is better than nothing.

Size & Weight

I want a light that is super bright, small, neutrally buoyant and self-contained battery (handheld)..oh and I’ll add cheap too. Pigs will soon fly past too…

Everything’s a compromise. Old school 50w HID lights proved themselves competent with ~5000lm of output, wide beams and solid burn time. What you had to deal with was bulky light heads, cables and heavy/monster size battery canisters.

Today, LED technology has helped significantly, but is still not magic. Depending on who you believe, LEDs are about 30-40% more efficient than HID bulbs. What this means is our battery packs can be smaller, and when you use  high-density lithium technology instead of NIMH batteries, you can get your canisters real small or even integrate it with the light head.

LEDs are also tiny and don’t need a big reflectors (like HID bulbs), meaning light heads can become extremely small and light.

Self-contained, or handheld lights have become very popular because quite frankly, cables suck. The problem is that a handheld light is negatively buoyant and this weight is positioned high on your camera setup. Your rig then becomes heavy and instable. Of course, if you need extreme output or long burn time, cables and canisters are now your friend.