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A6500 enclosure buoyancy characteristics

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Hello everyone.

 

Has anyone used the Fantasea or Nauticam enclosures for the Sony a6500?

If so...I am wondering what the buoyancy characteristics are of the enclosure you used...I cant seem to find any info on this online and I am trying to decide between the two.

 

Thanks!

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There is no single definitive number for this, as it very heavily depends on what ports you have mounted on the housing - big domes displace more water than fisheye domes or flat ports - and what lens you have mounted on the camera, as the same port can contain lenses with dramatically different weights. Furthermore, buoyancy alone doesn't tell the whole story - your housing may be neutral, but with a hugely buoyant dome out front, and a heavy viewfinder in the back, it will keep trying to twist itself upwards. Conversely, with a heavy macro lens, it may try to dip the port downward. On top of that, buoyancy depends on water salinity - a 7kg rig that is balanced to be neutral in fresh water will be about 250g positive in in the ocean. In general, polycarbonate housings like Fantasea are somewhat positive, while aluminium housings like Nauticam are somewhat negative, but by how much depends on your exact rig configuration. My own rig (A6300 in a SeaFrogs housing with 10-18mm lens in their 6" dome; two SeaFrogs ST-100 strobes) ended up neutral and in good trim by using two 300g carbon float arms, two regular aluminium arms, and about 300g of adhesive lead weights on the dome.

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Any Images of your rig Barmaglot, and I am trying to understand the 300g offset in both buoyancy and weight. Does this mean that the rig was just about neutral other than the dome being light in the front. I do realize that this an old post, I am prepping a Sea Frogs Salt Line A6XXX with a Sony A6500 with a 10-18 in the 6" dome and a 90mm 2.8 Macro in the flat port. I haven't seen any post about this lens and the buoyancy be completely opposite or no weight just buoyancy correction. 

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Since that post above, I have moved from 6" dome to 8" dome, which is significantly more buoyant. Last time I dove it, I had it set up with about 450g of weight on the dome and no floats - just regular arms. Conversely, when I'm using 90mm with macro port and a focus light, I replace all four arms with 200mm length/60mm diameter carbon fiber floats. In both cases, the rig is slightly negative overall. However, I just got new strobes (Retra Flash Pros replacing SeaFrogs ST-100s) so I will likely have to readjust buoyancy once again.

What I do to dial-in the buoyancy is fairly simple - I have a box of stick-on tire weights, so after I've made a significant change to my rig, I put it in the water and see if it floats (the SeaFrogs housing and its ports are naturally buoyant; it's the accessories that drag it down). If it sinks quickly, this means that I need to add floats. If it sinks slowly, this means that it's good to go. If it floats, I take it out, stick on a few weight blocks (mine come in 7g increments) and try again until it starts sinking slowly. Don't rely on other divers' setups as an exact reference, because everyone's rig is slightly different - trays, arms, clamps, lights, strobes, wet lenses, action cameras, etc, all come with their own buoyancy characteristics, and even location matters - a rig that is neutral in fresh water will float in the ocean, and a rig that is neutral in the Pacific will float in the Red Sea.

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