Guide numbers & Power of S&S strobes

Hello,

I dive with a Oly 5060 with a PT020 housing and am looking at strobes. (Yay!)

Most of my diving is in So Cal with limited viz and lots of particulate matter, so most of my pics are/will be macro.

I'm researching Sea & Seas strobes and have this question:

I assume the strobe's model number is an indication of increasing power, however I have read (or thought I did) that the higher a guide number the higher the output so I'm confused by the following:

YS 90 - GN 22

YS 55 - GN 18

YS 25 - GN 49.5

YS 15 - GN 12

Why does the 25 have the highest GN?

thanks

-Renee

Several reasons could be:

Feet vs meters

air vs water

some variance is also due to a narrowly focused strobe versus one which covers more area.

My suspicion with the YS25 is that it is giving you the results in air and distance in feet.

yes.....confusion begins with mixture of gn's in feet and meters....

YS 90, YS 55, and YS 15 posted numbers refer to the guide number rating of the strobes measured through air, measured in meters, sensitivity rating ISO 100. Measurements compiled by Sea & Sea.

YS 25 guide number you listed has been converted to feet (15 times 3.28). IOW, the metric guide number for the YS 25 for comparitive purposes is 15.

The guide numbers for each strobe listed will diminish once the light is forced to travel through water, which is much denser than air.

Not sure why S&S chose those specific numerical monikers for each of their strobes.

And use those guide number ratings for comparison purposes only within the Sea & Sea line of strobes. Every manufacturer has their own technique for arriving at the GN rating. IOW, they do not all play by the same rules.

For more comparisons, try the Strobe Finder:

http://www.digitaldiver.net/strobes.php

hth,

b

Thanks,

I can't get to digital diver from work so I've been waiting not so patiently until I can get home and check it out.

-Renee