New lighting tests. Interesting resutls. as per usual.

[DJ88]

what formulae would I use to convert the 3" results to 18" results

<font size="2" face="Verdana, Helvetica, sans-serif">Drum roll please.

From Sanjay's site about MH testing that YOU posted in another thread. :D

Do you ever read any threads Steve? ;) hee hee. Kidding. :D

The Inverse Square Law-
Being a point source of light, as you get closer to a MH bulb the intensity increases at a rate of the square of the distance. In the tests performed to get the above numbers the distance from the sensor to the bulb was 18 inches. As bulbs are placed closer to the water surface the PAR numbers will increase dramatically. If the bulbs are placed at 9 inches above the water multiply the above number by 4 (eg Iwasaki 400w 173 x 4= 692). Move them to 6 inches and you can multiply by 9 (eg Iwasaki 400w 173 x 9=1557). This particular bulb is approaching natural surface values without even using a reflector.