Spilled coffee grounds, weather, wine, and underwater photography.
In this post, I intend to connect the virtues of a vacuum with underwater photography. But first, let’s talk about what a vacuum is.
Most people’s first encounter with the word was probably related to the ubiquitous “vacuum cleaner”. This appliance uses a vacuum to move crumbs, dust, dirt etc from your living room floor into a bin or bag that you can throw in the trash. But what do we mean, exactly, by the term vacuum? As a physics nerd, I want to say that a vacuum is a space that is devoid of all matter. This is really more of an ideal condition that we use for physics calculations. More practically, a vacuum condition is one where the air pressure in an area or container is less than the surrounding pressure. And as happens with a pressure difference, air will flow from the high pressure area to the low pressure area if allowed to. So in the vacuum cleaner example, the lower pressure inside the machine causes air to flow into the machine, very effectively picking up those coffee grounds you just spilled.
Low pressure in our atmosphere has a huge effect on our lives. Just as the air wants to flow into the vacuum cleaner, so too does air flow from high pressure to low pressure systems in the earth’s atmosphere (though the Coriolis effect makes the wind flow more around low pressure rather than directly into it). This is the basic mechanism for wind, whether it is a nice afternoon sea breeze or a tropical cyclone.
There is something to be said for having a glass of wine while you cull photos from today’s underwater photo shoot. Do you have one of the little wine saver pump/valve kits? These use the vacuum concept to help save your wine from going bad. How? By pulling a vacuum inside the bottle, the wine is exposed to less oxygen. (other gases too, but oxygen is the main culprit). Less oxygen means less oxidation. How effective this is could be debatable, but my experience has been that it works well to extend the life of the bottle for a couple of days. On the other hand, you could just finish the bottle every time and skip the vacuum. Your choice.
So what does all of this have to do with underwater photography? As you know, one of the big challenges is keeping water outside of the housings that we use for our cameras. Wouldn’t it be nice if there was a way to have an independent and safe way to check the watertight integrity of the housing? Well, there is, and we use vacuums to do that check.
My first encounter with this idea occurred in 2005 when I was a deckhand on the “Spree”, a liveaboard scuba dive boat that was at that time working the Flower Gardens Banks off the coast of Texas/Louisiana. On this particular trip, we were host to Howard and Michele Hall, who were making a film called Deep Sea 3D for IMAX. The camera they were using was a 3D IMAX film camera. It used two giant reels of IMAX film which could capture 7 minutes of footage. The housing was about 4 feet tall by 3 feet wide and weighed 1800 pounds. We installed a crane on the boat to deploy the thing. After loading the (very expensive) camera and film, Howard and his crew used a vacuum system to verify the housing was watertight, first by pulling a vacuum and then monitoring the pressure over the next hour or two to see if it lost any vacuum. I remember watching how meticulous they were with this, recording the pressures at different times.
Nauticam has taken the concept a step further and made doing a vacuum check on your underwater camera housing quick and effective. To do this, they use a small electronic board to light up an LED to give you status at a glance. The main thing you need to know about the LED colors is that “Green Means Go”. Any other color means you need to fix something. The Nauticam vacuum board also incorporates temperature compensation. This stroke of genius allows you to safely pull the vacuum in one temperature (i.e. your air conditioned room) and take it to the dive site at a different temperature without a false alarm (or perhaps worse, a false indication of watertightness).
Having worked with a lot of people at workshops or on my trips who’ve had these systems, I can offer some handy tips
Try to pull the vacuum at least 1/2 hour before your dive. This gives a slow leak enough time to show itself. Longer is better, and you can even do it the evening before. Wake up in the morning to see a green light and you are good to go.
Most leaks will show up immediately, i.e. you won’t be able to even get the green light to come on. But some leaks are very small and take time to appear. Make sure to recheck the color just before entering the water.
Keep in mind that the vacuum system is only a check. You must still check/clean your o-rings, latches etc. The vacuum will not stop a leak, and it is possible to have a green light and still get water in the housing.
Nauticam has produced two types of vacuum valves. The older version had a nut you had to tighten to close it. The newer version has a push button with a spring that closes itself. Both have a separate cap. Get in the habit of always closing the nut on the older version immediately after letting the air out to open the housing. And for both, replace the cap immediately as well. I repeat, make this a habit.
The batteries for the boards last for hundreds of dives, but I recommend keeping a spare or two in your save a dive kit. The LED ight will flash red/blue when your battery is low.
Forgot your vacuum pump? These days, most dive boats will see multiple Nauticam housings onboard. Maybe you can borrow one. In a pinch, you can actually pull the vacuum with your mouth, especially on a small housing. If you have a large DSLR or beyond, you probably would get pretty light headed doing that by the time the green light comes on. Of course, if you are well prepared, you’ll have your wine saver kit with you too; you might be able to use the wine pump to pull your housing vacuum. But, some wine pumps don’t work, so don’t count on this without trying it. And, of course, remember to drink your wine after the dive, not before.
Thanks for letting me geek out about vacuums.
Here is a dolphin picture for you.
Chris Parsons and his partner Rima live on their sailboat, enjoying the 70% of the planet not covered up by land. Chris leads about 4 trips a year to great destinations (including a Reef Photo Workshop in Anilao, May 2019); check them out at http://chrisparsons.me/trips.