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Choosing a video light for your Underwater Video Rig

I thought of writing a brief article about video lights.

In the last years LED lights have become incredibly cost effective and there are many products on sale that look promising and cheap.

A special mention goes to the GoPro a very cost effective option for underwater video plagued by poor performance in low light. The GoPro market seem to have injected new life into the video light marketplace and of course calls for products that are not expensive in line with the typical profile of the GoPro user.

There are many examples of footage with what you would consider powerful lights that actually do not look that bright or even nice, why is that?

Lights are now measured in Lumens which is the SI unit of measure of luminous flux a light is said to emit one lumen if it emits one candela over a solid angle of one steradian. This sounds all very complicated and not very helpful so let’s try to make some sense of this.

Usually when we go an buy a light we are given three key pieces of information:

  1. Lumens – this in a way is considered the power of the light*
  2. Beam angle – this is the maximum horizontal beam that the light can cover – note this does not relate with solid angles but is merely a 2D view
  3. Color – this represent how white is the light, a good light should not exceed 6500K which is what is considered a day light white

*we will see that this is actually incorrect

Let’s have a look at a typical best buy the Archon Video Light W38VR, this light is declared to have the following:

  1. 1400 Lumens
  2. 120 degrees beam angle
  3. 5000K temperature

Looking at the specifications this looks like a very warm (5000K) wide beam light and very powerful so how comes that with a subject at one meter or 3 feet distance this light seems to have no effect on a bright day?

The reason is that lumens are not a real indication of the amount of light that hits the subject but just the total light emitted which includes the light that illuminates the water between us and the subject that we actually are not interest at all in illuminating.

If you had to do a video production in studio you would be looking at intensity of 1000 lux where a lux is measured in lumens/m2. The lux is the density of light that hits a flat surface at a given distance.

With a few calculations we see that the Archon light because of the very wide beam is effective at two feet and produces around 1200 Lux which is great however at 3 feet this drops to 550 Lux which is not that great.

Many times when comparing the new cheaper lights to expensive lights like Sola or Fix  despite the less nominal lumens declared the sola or fix seem brighter at the same distance.

So let’s evaluate the lux produced by a Sola 1200 a light much more expensive than the Archon with only a 60 degrees beam.

At two feet the sola produces around 4000 Lux which would nearly tan a fish, at 3 feet it still produces nearly 1800 Lux dropping to the studio value of 1000 Lux at a distance of 4 feet or 1.2 meters. This is because the illumination is in a smaller and narrower beam and is like the light was more dense.

Of course this has the disbenefit of a narrower beam so we need to step away from the subject in order to cover it properly, this diagram gives an idea

Typical Wide Angle Light Set up
Typical Wide Angle Light Set up

The two set of lines contain the video lights beams, we can see that those beams cross and them keep as combined angle of coverage the same beam of the lights themselves, that is the ideal spot for our lights as there are no shadows there.

Another consideration is the angle of coverage that we need for our camera lens to follow the lights, two 60 degrees beam lights actually cover a 100 degrees diagonal lens or 90 degrees horizontal lens typical of a 18mm lens. The GoPro and all compact cameras with a 100 degree lens fall in this group.

Another consideration to be done is that due to the light angle of coverage there is a minimum distance to be kept if we want to avoid our subject to be in the shade, this minimum distance depends on the light beam and the distance between them.

Once you get closer than one foot it is not necessary anymore to point the lights forward as the amount of water is limited and the lights can be pointed directly at the subject like in this example

Monopod front Macro Light Position
Monopod front Macro Light Position

So assuming we want to be at a distance of one foot or 30cm how far do the lights need to be?

For a 60 degrees beam the lights need to be 36 cm away or around 12 inches. For a light like the Archon with 120 degrees beam the distance between the arms needs to be 1 meters or 40″. Considering a tray is around 30 cm or 12″ this means you need arms at least 13″ in order to cover something at one foot and to cover a subject at 2 feet you need two meters distance that means again 33″ worth of arms.

What happens if you only have the tray with the lights on and your subject is at 3 feet with two very wide video lights of 120 degrees beam?

  • You illuminate already after 3″ from the camera
  • The two lights emit 550 Lux that combined are not such a small output

The net result is that a lot of the water in front of the subject is illuminated and this creates backscatter where all the silt in the water gets reflection and ultimately deteriorates the quality of the footage.

If you ever wonder why underwater photographers that shoot super wide have two 16″ arm segments this is why the want to avoid backscatter with their 110 degrees strobes and still be around one foot distance with their fisheye lens.

So what are the conclusions that we can draw:

  1. A wide beam light is only good if you have long arms, the wider the beam the longer the arms otherwise the beams just light up the particles in front of the subject producing backscatter
  2. Lumens are not a real indication of the effectiveness of the light per se but need to be taken into account with the beam angle and a lux calculation needs to be performed you want to aim for 1000 lux at the distance of choice
  3. Light beams need to be evaluated together with the camera lens horizontal field of coverage 60-80 degree beam angles are adequate for most of the video rigs out there and more is only justified for fisheye type of lens not commonly used in video

I hope you find this information useful and get in touch if you want to discuss, the subject is not that simple!

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20 thoughts on “Choosing a video light for your Underwater Video Rig”

  1. Excellent write up. It’s interesting how the video light arms race mirrors the megapixel count of the cameras.

    I’m looking at two lights with the same reported 2500 lumen output. The $800 light has a 90 degree beam while the $400 light has 120 degree beam. Do you think that the difference would be worth $400?

      1. You are correct, the $800 light is the Sola 2500, the other being the Big Blue VL2500P.

        I plan on shooting green water muck wrecks and wildlife about the size of a deck of cards. Visibility ranges from 10ft – 40ft.

        I honestly don’t know how much light I actually need. Maybe I only need the something like the Sola 1200 or 800.

        Thanks again

  2. I was looking to maybe mimic your LX7 build, but it’s unlikely that I’ll initially have anything other than the stock lens. If I go all out, then I’ll probably use your RX100 II as a guide.

    1. For my LX7 build a pair of Sola 1200 are perfect or if short of money even a pair of Sola Dive 800 (currently $399 great price) both lights work as spotlight which is very very useful. There is not enough lens field of view to do anything with wider beams. Two 60 degrees lens cover more than 90 degrees horizontal and on the LX7 this is as much as you get. Likewise on the RX100 unless you want to shoot with a fisheye

      1. Perfect. I’m really just looking for a step up from a GoPro. I want a an LCD Screen and be able to get better close up.

        The only thing that keeps me from jumping into an LX7 build is the housing cost. For $200 more than LX7/ikelite, I can get an RX100 II/Ikelite.

        I don’t have an RX100 II yet because it seems that I’ll need extra wet lenses right out of the gate, exceeding what I can afford for the initial start up cost.

        First world problems, I know.

      2. I don’t recommend the ikelite in cold water it is very hard to operate with gloves. Get an Lx7/Nauticam as a start you can get an ex demo housing if you ask shops around or look on ebay. If you are interested I offer a personal shopper service at £30…many happy customers avoiding expensive mistakes

    2. Another observation
      I notice is that the bigblue lights are really negative (184 grams 6.5 Oz) and are therefore not suitable for mounting on 1/2″ locline arms in fact the come with ball mounts
      Once you add ball arms (that something like the sola don’t require) you have added $150 for a few clamps and arm segments which are also more negative so now you need more floats than before

      1. What if you put a little foam/float around the light itself?

        I’m surprised that there aren’t more lights with narrower beam patterns. I like the Sola 1200’s and while there are other lights that are cheaper, the beam patterns are almost all twice a large ~110/120 degrees.

        Have you noticed any cheaper alternatives to the Sola 1200’s with a comparable beam spread?

      2. The foam would be useless as the 1/2″ locline would not hold the weight on land 395 grams is heavy like a strobe. You would need 3/4″ locline segment but in any case there is no locline mount so back to the ball and arm, say one 5″ and one 8″ segments and 3 clamps plus base $205 gone. So you are now at $605 per light with arm. Not as cheap as it looked as a starter and you do need wide arms with a wide beam light. Sola are small and light and work fine with a locline arm that for the same length will cost $39 including the mount uhmmm

  3. Thank you so much. These are the insights that will save me in the future!

    Have you looked at the ikelite vega?

    1. No I haven’t really, I have had my Sola since one and half year and I never felt I was missing anything. They are small and work as spotlight, I would not get a light that only works as flood as I need the spot for macro work and as a dive light, so that saves me holding a torch

      1. On a night dive for example because if you put flood on annoy all kind of fish and the other divers and for macro
        If you have a flood light only you need an additional torch for night dives. If you don’t do night dives and only shoot wide angle you don’t need a spotlight

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