Approaching neutral buoyancy for new rig

Hi all -- I've recently purchased my first compact system (an LX10 in Nauticam housing+flexitray) and I'm hoping to get some advice on the steps and options for making it neutral for both a macro and wide angle video set-up. In case helpful, these are the components I have for each:

• Macro -- housing + tray, UCL-05L +6 lens, two small video lights, quadripod
• Wide angle -- housing + tray, Inon UWL-09F lens (just using ambient light)

Here are my specific questions:

• What steps do you take to figure out how much buoyancy you need / amount of negative buoyancy to compensate for? 
• For wide angle, should you aim to make it perfectly neutral? For macro, I understand you want it to be slightly negative -- how much?
• How can you most effectively test out your solution before going on a dive? I've seen some people in other threads say they tested in a pool, but others have said that the different densities of fresh vs. salt water will make a difference. 
• Any suggestions for the most flexible and affordable floats for adding buoyancy and how best to position them?

If there are any other thoughts beyond the above, I'll take any and all advice I can get! I've searched through the forums, but if I'm missing any gems, please do point me in that direction as well.

Many thanks!

Hi!

This has been discussed a lot so definitely worth a good search. 

Generally the easiest way to calculate how much buoyancy you need to add: assemble all your gear then, in water (preferably sea water), hang it on one of those handheld luggage weighing devices and see how much it weighs. This will give you the negatively buoyant weight in water. From this you know how much positive buoyancy you need to add to get it roughly neutrally buoyant.

I don’t think it makes any difference whether you are shooting WA or macro in terms of how buoyant (or not) the system should be.

I’d suggest you want it very slightly negatively buoyant. If you let go or drop it, the system will drift downwards very gently at a speed you can likely catch it. The problem with positive buoyancy is that if you let go and your system reaches the surface, it will be very hard to find in the waves or looking up against the sun.  

If it drifts down SLOWLY, you should be able to spot it and catch it.  If you do lots of wall dives or dives over very deep seabeds you do need to be extra careful - but, on balance, I think that is preferable to a system heading to the surface,

As to what to use for the additional buoyancy, I like Stix foam which is relatively inexpensive, lasts well and is easy to change depending on port/lens combination. Others here will point you at float arms. It’s personal preference and budget. 

Hope this gets you going….
Here's one link:

View archived post in: Float Arm choices?

12 hours ago, shelbyrose said:

Hi all -- I've recently purchased my first compact system (an LX10 in Nauticam housing+flexitray) and I'm hoping to get some advice on the steps and options for making it neutral for both a macro and wide angle video set-up. In case helpful, these are the components I have for each:

• Macro -- housing + tray, UCL-05L +6 lens, two small video lights, quadripod
• Wide angle -- housing + tray, Inon UWL-09F lens (just using ambient light)

Here are my specific questions:

• What steps do you take to figure out how much buoyancy you need / amount of negative buoyancy to compensate for? 
• For wide angle, should you aim to make it perfectly neutral? For macro, I understand you want it to be slightly negative -- how much?
• How can you most effectively test out your solution before going on a dive? I've seen some people in other threads say they tested in a pool, but others have said that the different densities of fresh vs. salt water will make a difference. 
• Any suggestions for the most flexible and affordable floats for adding buoyancy and how best to position them?

If there are any other thoughts beyond the above, I'll take any and all advice I can get! I've searched through the forums, but if I'm missing any gems, please do point me in that direction as well.

Many thanks!

Every setup is a little different, that's why weighing your rig is the best bet.   You might need to cobble it together to weigh before you have the chosen float arms.  The difference in density is about 3% so unless you are right on neutral you won't notice the difference.  Put everything in a spreadsheet and work out is needed for each configuration to get neutral then go to work to pick out your flotation.

The big problem with positive buoyancy is it's unstable UW, I did a dive with my rig that was around 100gr positive one time and it kept trying to twist up, made it significantly harder to aim.  To be stable the rig needs to have the flotation above the housing. 

Realistically the Kraken adjustable floats are the the only really convenient option to get right on neutral and you adjust them on site to get the buoyancy right. 

I almost agree on everything with Tim and Chris. Almost

- Never mind the difference between fresh and salt water. Grab a suitcase scale and dive it in a pool/sea/lake.

- If you are budget sensitive and don't deep dive, Stix are the most flexible solution to quickly have two configurations.

IIRC you will shoot video and there are small but important differences to keep in mind between photo and video use.

In a photo you have to stand still for about 1/60th of a second. In a video shot you need to be steady for at least 30 seconds. This is the most underrated thing and you should try it in the water.

I disagree about having the same buoyancy between wide and macro.

Macro with video is mainly accomplished through the use of a tripod. Depending on the type of tripod, bottom and how you are forced to position the lights, sometimes the whole thing becomes unbalanced and doesn't stand and you are forced to hold it with your hand transferring imperceptible vibrations to the footage. Add to that the current factor. So I would say the macro needs to be heavier but not so much that it ruins your dive to carry it. I carry with me hooked to a d-ring on my jacket an extra 500 gram weight with a bungee and bolt snap. If the whole thing is not stable on the bottom, I attach it to the housing handle on the fly.

We only talked about buoyancy but not trim. It is correct to say that the float should be placed at the top (think of a sailboat) and many have suggested using a cross float bar between the two handles. Just be careful not to overdo the height (vertical distance) and buoyancy relative to the weight of the case. If you overdo it, the assembly will tend to have a well-defined position relative to the plane. To shoot a subject upward or downward (even slightly) you will be forced to exert a constant force with your wrists. Again you will inevitably transmit lots of vibrations to the whole kit.

Oops..... I missed that shelbyrose was shooting video. Sorry! (Two out of three ain't bad?)

Yeah, a difference then between shooting WA and macro. Apologies, I was thinking of it from a stills angle where I think there is no real difference.

I think as a starting point this is worth to watch.

Just browse their channel, there is an entire playlist dedicated to uw video tutorials and some very interesting QA videos.

8 minutes ago, TimG said:

Oops..... I missed that shelbyrose was shooting video. Sorry! (Two out of three ain't bad?)

There are so few of us that I tend to remember and cuddle them