Underwater Light Meter

A friend is trying to assess is new lighting in a large pool-like structure and they want to measure light intensity inside the structure. I have looked but cannot find an underwater light meter. Do such devices exist? If not, since the pool is only 23 feet deep, would it work to put a light meter in a waterproof pouch like those made for iPhones?

Thanks.

Don

I do volunteer work for the New England Aquarium and they are planning a major renovation of their main exhibit, the Giant Ocean Tank. One issue they are trying to assess is new lighting and they won't to measure light intensity inside the exhibit. I have looked but cannot find an underwater light meter. Do such devices exist? If not, since the exhibit is only 23 feet deep, would it work to put a light meter in a waterproof pouch like those made for iPhones?

 

Thanks.

 

Don

The need a PAR meter (Photosynthetically Active Radiation). Some have meters that are water proof (but not a 23 foot cord). I would think you could put it in something that would withstand pressure. I'm surprised an aquarium as well known as that one doesn't have its own PAR meters. Google PAR meters and you'll find a lot to read about.

Ikelite used to make one - the #4200 Digital Exposure Meter. There may be others.

However, you should be able to use a regular camera in waterproof housing, with a white semi-opaque bulb covering the port. Calibrate ISO/shutter/aperture on the surface to a standard light meter reading, and then take measurements with the camera's exposure meter underwater. Match the underwater exposures to your calibrated measurements to determine your ambient light (note, there may be some shift for meter WB correction).

Steve could be right, though, if they're trying to figure out how much more light is required to sustain photosynthetic life at depths.

Sekonic makes (made) an underwater light meter called the L-164 Marine. You can rent one for a reasonable day rate here:

http://www.alangordon.com/r_lightmeters.htm

I hope this helps.

Randall