Hi Claude,

Unfortunately, published footcandle measurements for orchids are for
natural daylight at noon in greenhouses. This means that morning
light levels will slowly increase to the maximum at noon and then
decreas until dusk.

Flourescent lights are on 100% intensity for the duration of the day
so the total number of photons hitting the plant over a 16 hour day at
a measured value of 600 fc under flourescents may be equal to the
light a plant gets in the greenhouse with 1000 fc.


Also, (I may be wrong on this) I don't thing light meters for sunlight
accurately read the light coming from flourescents since the
fluorescents only produce a few wavelengths of light (blue GREEN
red)[mostly a green peak plants don't use very well] where as sunlight
has a continuum of wavelenths (rainbow).



The general (cheapest and fairly efficient) fluorescent light settup
for orchids is 2-48" shoplights (= 4 tubes; giving about 800 fc) on
for 14-16 hours/day, with Phals placed about 8-14 inches under the
lights. 20" fixtures put out much less light = your low readings
(count up the watts to get an idea of the energy your plant is
getting). They are OK if the plant is getting some window light and
you are tight on space.

After 8-12 months the tubes start putting out WAY less light even
though the human eye doesn't recognize it.


Hope this helps.




"PhalGuy" wrote in message ws.com...
Hello all!

Today I bought a light meter to be able to get a measure in foot-candle of
my fluorescent.

I have read in books that Phal are best grown between 900 - 1200 feet candle
during summer time and 1300 - 1500 feet candle in winter time.

Last year, I have bought 6 20 inch long Bright Stick GE Sylvania Grow and
Show for my phal.
When I took my measurement today, at 1/2 inch from the light, I was getting
around 200 feet candle!!!!
I tried with a regular 60 watts incandescent bulb and I got 500 feet candle!

Here`s my question:

In two weeks from now, I`m changing my light fixture for 3 48 inch long 2 X
40 Watts fluorescent tube.
If I put two Daylight 40 watts tube, am I going to get the necessary feet
candle for my plants?
Would it be better if I put one ColdWhite and 1 WarmLight ?

I am so confused! I just want my plants to be happy and to finally spike!

thanks

Claude