The spacing between fixtures depends on the lamp power, power setting, and type of crop. Most crops require at most
1500 μmol/m./s of photosyntetic flux. The next table lists the minimum footprint size to obtain at most 1500 μmol/m./s
at the crops, for common power settings.
You can adjust these numbers for different power settings and for different desired flux at the crops, using this formula:
area = power / 770 For example: 0.80 m. = 720W / 770
The number 770 is estimated from the expected light output of the lamp, with reflector and wall losses taken into
account. Depending on your exact set-up, the actual number can be as low as 720, but rarely higher than 770. This
formula is intended to give you the minimum area, hence we use 770.
Note that 1.3 m. is not the same as a square of 1.3 by 1.3 m. The latter is 1.3Å~1.3 = 1.69 m. in area.
The minimum area determines the distance between the fixtures, and therefore, the amount of fixtures needed to place in
a multi-fixture growing room. For the calculation of how high your fixtures should be placed, see te next section.