Re: How to determine appropriate strobe size?

Posted by Dennis on September 29, 2001 at 08:17:31:

In Reply to: How to determine appropriate strobe size? posted by Robert on September 28, 2001 at 10:23:31:

: What advice can you give me regarding how to determine which size strobe to select. What do 22 watt seconds versus 33 mean in real language. I plan to use two with my Nikonos V.
: Thanks Robert

Robert:

The measure for quantifying light output is called a Guide Number, which every manufacturer specifies for their flash units, typically based on an ISO of 100. The larger the GN, the more powerful the flash. And this GN is also used in the formula for determining the f-stop for a manual exposure. And the more power you have, the smaller the aperture, and the greater the depth of field in the image.

Reality is, you can really only use these guide numbers to accurately compare strobes within that manufacturer's product line. A strobe with a guide number of 28 underwater is not necessarily equal to a strobe with a GN of 28 from a different manufacturer.

So, you try to go with as much power as is practical. Coverage is also an issue of course, depending on what type of photography you want to do.

For further assistance please call us at 800-334-3549 x42 or 312-421-6000 x42.

Dennis
Helix UW Photo Dept

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: : What advice can you give me regarding how to determine which size strobe to select. What do 22 watt seconds versus 33 mean in real language. I plan to use two with my Nikonos V. : : Thanks Robert : Robert: : The measure for quantifying light output is called a Guide Number, which every manufacturer specifies for their flash units, typically based on an ISO of 100. The larger the GN, the more powerful the flash. And this GN is also used in the formula for determining the f-stop for a manual exposure. And the more power you have, the smaller the aperture, and the greater the depth of field in the image. : Reality is, you can really only use these guide numbers to accurately compare strobes within that manufacturer's product line. A strobe with a guide number of 28 underwater is not necessarily equal to a strobe with a GN of 28 from a different manufacturer. : So, you try to go with as much power as is practical. Coverage is also an issue of course, depending on what type of photography you want to do. : For further assistance please call us at 800-334-3549 x42 or 312-421-6000 x42. : Dennis : Helix UW Photo Dept

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