trying to understand bulbs,lux and footcandles for orchids

[Katsols]

I've been trying to perfect my light. I have a big northwestern window that gets direct sunrays for two hours at 3pm.
Right now i'm using Sun System HPS 150 Grow Light Fixture which an internal ballast. After reading here and doing research and according to the image below seems like a metal halide is better than high pressure sodium. So i thought maybe i could get this Ultra Sun Metal Halide - 4200K Lamps | Sunlight Supply, Inc. - Indoor Gardening Supplies, Grow Lights, Hydroponics, and Lighting
or more expensive one
Eye Hortilux Blue Enhanced Perf. MH Lamps | Sunlight Supply, Inc. - Indoor Gardening Supplies, Grow Lights, Hydroponics, and Lighting
Do you think either one would be good? apparently according to this website the cheaper bulbs from small to the large one range from 50,000 to 100,00 lumens! and its 2000k Ultra Sun 901528 - 400 Watt - HPS Grow Light - 2000K
but according to the image 5500k is good, so i found this. Amazon.com: EYE 57945 - 1000 Watt - T120 Grow Light - Hortilux Blue - Metal Halide - Reduced Envelope - Unprotected Arc Tube - 5500K - ANSI M47/E - Horizontal Burn - MT1000B-D/HOR/HTL-BLUE: Home & Kitchen but i'm not sure if it will fit with my fixture.
Eye lighting has some nice bulbs. One bulb is 42000 lumens which is about 3901 footcandles when i converted but it is not 5500k, instead it says 3500 (V)4000 (H) would it still be ok? (if it fits my fixture) Now how can the cheaper lamp be so many lumens compared to eye lighting, i'm so confused on what to get!

p.s. i read up that for example vandas need about 2500 – 4000 footcandles and i have two so i need a bulbs between 3000 to 4000 lux according to my calculations. I think my high pressure sodium is 150 watts and some MH bulbs are about 100 watts, could you help me understand watts and how it's related to light strength?

[Ray]

May I ask what you mean by a lumens to foot candles conversion? Lumens are units of emitted light, while foot candles are light intensity per unit area ( a FC is one lumen per square foot).


Ray Barkalow
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[Katsols]

I used a lux to footcandle calculator online

[DavidCampen]

And, in addition to Ray's comment - the lumen measurement is weighted to the sensitivity of the human eye which is quite different from photosynthetic effectiveness. So lumens can be used to compare the realtive photosynthetic effectiveness of lights with the same spectral output but it becomes less accurate when comparing light sources of different colors.

---------- Post added at 03:37 PM ---------- Previous post was at 03:35 PM ----------

Originally Posted by Katsols

I used a lux to footcandle calculator online

Lux is lumens per square meter.

---------- Post added at 03:40 PM ---------- Previous post was at 03:37 PM ----------

Will your existing HPS fixture handle MH; does the ballast have a switch to convert from HPS mode to MH mode? I certainly doubt that you would be able to run a 1000 watt MH in a 150 watt HPS fixture.

[Katsols]

Originally Posted by DavidCampen

And, in addition to Ray's comment - the lumen measurement is weighted to the sensitivity of the human eye which is quite different from photosynthetic effectiveness. So lumens can be used to compare the realtive photosynthetic effectiveness of lights with the same spectral output but it becomes less accurate when comparing light sources of different colors.

---------- Post added at 03:37 PM ---------- Previous post was at 03:35 PM ----------



Lux is lumens per square meter.

---------- Post added at 03:40 PM ---------- Previous post was at 03:37 PM ----------

Will your existing HPS fixture handle MH; does the ballast have a switch to convert from HPS mode to MH mode? I certainly doubt that you would be able to run a 1000 watt MH in a 150 watt HPS fixture.

hmm.. Maybe.. I did find some 100 watt MH bulbs as well. I'll email the company that made the fixture and ask them if I can use MH.
P.S. did some research and i found out that i can use a metal halide, to be specific Ultra Sun Metal Halide 150W conversion bulb.