Raising the light fixture

Hello everyone

Ok so my question today is... Would raising the light fixture really decrease PAR values that much? When the manufacturer states PAR values at 12" and then 24" they are showing the light values moving through 12" to 24" in water, correct? Does air really block a noticeable amount of light over say 4"?

I would like to raise my light fixture to help with light spread and decreasing the disco effect. Would I really be limiting the PAR reaching the sandbed by a noticeable amount? Thanks!

 

By increasing the hight you are increasing the spread of each individual light (think of a cone) so yes, PAR will be reduced.

 

That makes sense. Do you think we are talking a 5% loss or 20% loss when raising a fixture 4"?

 

The general rule is by doubling the distance you decrease the amount for light by a factor of 4. That's in air. Water absorbs light much more. So if you doubled the distance to the surface, the amount of light at the surface is 1/4.

 

Thank you for the info. I will do some calculating and see if it is worth raising the fixture.