There are many things that have to fall into place to achieve the perfect underwater photograph. It starts as soon as you begin planning the trip. You’ve purchased the top of the line camera, bought your plane ticket, booked the dive, now you find yourself 100 feet below the surface staring at what you believe is going to be it. Your best shot to date! In 1597, Sir Francis Bacon noted in his memoirs "scientia potentia est“ or “knowledge is power”. Truer words were never spoken and we hope the information in this article will give you an edge, another way of making sure all that time and money yields a return on your investment.
In this article I'll discuss the pros and cons of shooting continuous lighting systems underwater vs the standard underwater strobe setup. Before we get into this, lets talk a little bit about light, water, and why it’s important to understand how these two factors will ultimately effect your image.
Ironically, the one thing we absolutely can not dive without happens to be one of the biggest enemies of the underwater photographer. You guessed it, Water! 71% of our world is covered in it, and water happens to be everywhere I like to dive, funny how that works out.
So, why is water the enemy? It’s pretty simple. Water absorbs light, and we need that light to reach the little sensor inside our camera body to properly expose a photograph.
It’s also important to understand that water absorbs light at different rates, depending on the wavelength of the light.
The ocean looks blue because red, orange, and yellow (long wavelength light) are absorbed more easily by water than blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned.
Okay, so now that we have that out of the way, let’s geek out a little and discuss the Inverse Square Law. Not to worry, this sounds much more complicated than it is. For those who are into math, here’s the equation.
This law states that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.
Stated in more simple terms; as light travels over distance, it becomes less intense. Now if you’re thinking, “I didn’t need a physics lesson to understand that!”, you’re likely correct. However, it is worth understanding just how quickly light will lose intensity over distance.
For example, if you were to have two subjects in your image, one exactly one meter away from your camera and the other exactly 2 meters away, how much light would the second subject receive in comparison to the first?
The second subject is twice the distance away so we take 2 and square it. This gives us 4, the inverse of which is 1/4. Even though the second subject is twice the distance from the camera, it receives only 1/4 of the light. Always keep this in mind, especially when you are trying to light multiple subjects.
Back to the topic. Is there an advantage to shooting video lights for underwater photography?
Firstly, let me start by stating that video lights are never going to light a scene like underwater strobes. Strobes will give you an effect that video lights can never achieve, or at least with todays technology. Powerful strobes have the ability to flood the foreground with light, keeping the background nice and dark. Dual strobes can also light both foreground and background by working independently of one another with manual power settings. This is easily done with my Ikelite strobe setup.
Before you get overly excited, even these amazing technological devices have their draw backs. Strobes have a recycle rate, “typically less than 2 seconds”. This is the time it takes a strobe to re-charge before the next fire. High speed firing can often result in a well lit image followed by a terribly underexposed image.
Underwater strobes also have a maximum sync rate. This sync rate will limit the amount of shutter speed you can shoot in your camera if your shooting TTL. For example, Canon has a maximum sync rate of 1/200 of a second and Nikon 1/250th. And last but certainly not least, strobes can be HEAVY! My Ikelite DS-161's weigh in at a whopping 2 lbs 14oz EACH!!
Now onto the video lights. Lets start with the most obvious advantage. Video lights allow you to shoot video!! Imagine that! Underwater strobes can’t help you here. Video lights are also much lighter than most strobes. My Hi-Max UV-9 10,000 lumen monsters weigh in at just over 1 lbs each. Another advantage to continuous lighting is that it requires no connection to the camera. If you’re really creative, you can even detach them from the rig and light something off in the distance, creating a unique composition that is difficult or impossible to recreate with a strobe.
All of this is well and good… but really… so what! I can carry the weight of two strobes and two video lights. I like the effect of the strobe on my images. I also like to be able to switch into video when the moment presents itself.
The real advantage in shooting underwater photography with continuous lighting is frame rate. Stick with me here, I'll try and stay away from anything too geeky.
My Canon 5D Mark3 has built in, as most all DSLR's do, a high speed continuous function. This allows me to shoot 6 frames per second. When interacting with moving subjects, this can be a critical piece of the puzzle when you're trying to get the perfect shot.
So how does this work? It's pretty simple. Because there is no connection between the camera and light source, and because the video lights are always on, your camera can fire at will without the worry of missing the shot due to a slow recycle rate.
I like to custom white balance my camera in this situation. It's not necessary if you're shooting RAW, but if you need to make a quick switch into video mode, the cameras ready to go. I’ve found that the best way to achieve this is to use the sand. Here in the Cayman Islands, our sand is beautifully white. My process is as follows:
- Turn the camera to full auto mode
- Turn on your lights
- Find a place where the sand is exposed to the sun
- Make sure your lights are illuminating the sand
- Take an image
- Turn the camera into manual mode
- Select the CWB option and select the last image
There you have it, it’s that simple. If you don’t have white sand, simply use a white slate instead.
With new mirrorless systems like the newly released Panasonic GH5, available from our friends at Blue Water Photo, photographers have the ability pull 18 MP jpegs from the 6K photo-mode at a rate of 60 frames per second! If ever there was a time for continuous lighting, this is it! Oh yeah, one last thing. In this situation a CWB is 100% necessary as RAW is not avaiable in this mode.
About the Author: Jason Washington is the managing director of iDive Global Ltd and the co-owner of Ambassador Divers, a PADI Five Star facility located at the Comfort Suites Resort on Seven Mile Beach. Living and working on Grand Cayman as an underwaterphotographer/SCUBA instructor for the past 20 years, Jason's work has been featured in numerous documentaries and feature films.