By John Brigham
Neutral buoyancy and perfect trim are important to underwater imaging whether you’re shooting photos or video. Large diameter dome ports are the right choice for split shots (half-in, half out of the water). Ikelite produces the lightest 8” diameter dome ports underwater to optimize your travel baggage allowance. But that big pocket of air needs a counter-balance. That’s where the Trim Weight System # 47140 comes in.
Watch the video or read the article to find out the why and how of trim weight underwater.
Why to Use a Trim Weight System
As an underwater photographer, especially if you're a scuba diver or freediver, you're probably very cognizant of the travel restrictions imposed by the airlines. In the United States it's often 50 lb (22.6 kg), but it can get down as low as 30 lb, depending on how remote your location is. Because of this, we've designed our full size DL 8" Dome Port to be as lightweight as possible. You'll want to use this full size dome port if you're shooting wide angle, especially rectilinear lenses, to get the sharpest image possible. The full size dome is also critical for shooting split shots (half-in, half-out of the water).
The displacement of the large dome port in the water creates increased buoyancy on the front end of the housing. Depending on the weight and length of your lens, you may find the dome wanting to pull up.
Selecting a Weight to Use
The trim weight system is unique because it uses a standard scuba weight instead of an expensive specialized piece of lead. The amount of weight you need is going to depend upon what lens you're shooting. How heavy is it? How long is it? How many port extensions will there be? As a rule of thumb, 2 pounds (.9 kilograms) is a good place to start. You can always change out later. The best part about that using a dive weight is that you're going to find it on location. That means you don't have to travel with 2-3 pounds of dead weight in your luggage.
The last thing you want to be traveling with is a bunch of dead weight in your luggage. The Trim Weight System is unique in that it uses standard scuba weights available on location at most any dive site.
Attaching the Weight to the Rail
Attaching the weight to the rail is very simple:
- Take the strap with the hook away from the center, pull it up through the weight.
- Grab your rail. Feed the strap up through one slot in the rail and back down through the other slot.
- Feed the strap back down through the weight and through the buckle.
- Pull the strap nice and snug then wrap it around and back on to itself.
Attaching the Rail to the Housing
If you look at the bottom of the tray and handles attached to your housing, you'll notice a 1/4-20 threaded hole in the center. The trim weight screw will thread into this hole. The spacer sits in between the tray and the rail to allow the weight to move underneath the dome port.
- Insert the indexing post of the spacer into the side of the rail opposite the weight.
- Insert the trim weight screw through the rail from the weight side. It will go through the center of spacer and protrude from the other side.
- Attach the assembly to that threaded hole in the tray.
Adjusting the Trim of the System
You'll notice a very long slot in the rail. The rail is designed to move forward and backward for perfect trim based on the length of your dome port. Slide the rail forward when using longer dome ports and backward towards the center of the housing when using shorter ones.
Move your weight closer or farther from the base of the housing for the perfect balance for both longer and shorter lens and port combinations.
That's it! No tools required, and you're set to get in the water. If you're shooting the full size 8" dome, trim it perfectly with the Trim Weight System. It's extremely easy to assemble and will help keep unnecessary weight out of your luggage for travel. If you have any questions, email us today via email@example.com.
A properly balanced housing will reduce wrist fatigue and be more comfortable to swim with for extended periods of time underwater.
John Brigham is the Vice President & head of product development at Ikelite. He was born with a flair for design and an entrepreneurial spirit as son of Ikelite founder Ike Brigham. He worked his way up in the business and is a natural fit in the R&D side of things. John dives the equipment as much as possible to test product and put himself in the "fins" of the user. You may also find him on the other end of an email or phone call when you reach out for product advice and support. When he's not underwater he's flying drones, setting off rockets, training his German Shepherd "T2", and spending time with his family.