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Floatation Sony A7RIII/16-35GM and 230 dome


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#1 Peterpan

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Posted 17 March 2018 - 07:40 AM

Hello,

just picked up my new Nauticam A7RIII housing with the 230 dome for the Sony 16-35f2.8GM lens.

Does anybody using the same system and can give me a rough idea about floating arms? Using the system with 2 Sea&sea YS-D2 strobes.

Cheers

#2 ChrisRoss

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Posted 19 March 2018 - 05:55 PM

Don't have the system but get your self a luggage scale (they are pretty cheap and useful for travel) and assemble the rig ready to shoot and weigh it submerged in a large bathtub or barrel ,making sure it is 100% underwater.  The weight you record is how much buoyancy you need to get it neutral.  You probably want it slightly negative so add a little less buoyancy than what is indicated. 

 

The difference in buoyancy between fresh and salt water is pretty small, for an object that displaces 1000cm3 the buoyancy is 23grams or so more in salt water.    So use 2 to 5% less buoyancy than what is measured in fresh water. 

 

If you don't have arms yet  no problem, weigh the housing alone the specs say YS-D2 strobes weigh 40g each underwater, so need 40G buoyancy each to get neutral.  Buoyancy arms all have their Buoyancy listed in the specs then you have to get some weight for clamps on other connection which are generally quite light. Add up all your weights and and reduce it by 2-5% to get the amount of buoyancy you need then buy a combination or arms that is a little bit less than what you calculated.