Do you lose PAR over air?

[Palting]

I am thinking of raising my lights several inches to give me more work room. So, as the title states, do you lose par if you raise the lights? Thanks!

 

[psteeleb]

I am thinking of raising my lights several inches to give me more work room. So, as the title states, do you lose par if you raise the lights? Thanks!

yes and depending on your reflectors it can be significant

the lost PAR due to light difusion in the air is not as bad as water but the light will still diffuse and the more distance the more diffusion

 

[frankpayne32]

I have noticed a dramatic increase in PAR when I lowered my luminaire closer to the water's surface. Check my homepage for my build thread for progression pics and PAR readings if you are interested.

 

[ganjero]

Yes, distance makes a big difference otherwise everybody would have their metal halides reallly high and avoid heat issues, and probably use only one bulb to light big tanks.
Some reflectors help you concentrate the light in a smaller area and then you can raise the lights

 

[Palting]

Bummer. Thanks for the replies, guys. Guess the light stays as-is.

 

[billdogg]

Google the Inverse Square Law. It states that if you double the distance, the intensity is 1/4. Closer is better.