Confusion about Light Intensity with 125W CPF

[bosco]

Hello All,

I've recently built an orchidarium (2'x2'x4' tall) and am illuminating my orchids with a 125W daylight spectrum CPF bulb. To my dismay, I measured the footcandle intensity only to find extremely low light levels even 2ft from the light (200 ftcandles detected with a light meter set to read fluorescent light intensity). I noticed that [some] websites suggest light levels of at least 500-1000 ft candles for shade loving plants like Gongora, and higher light levels (1500-2500 ft candles) for most dendrobium species... However other sites suggest lower light levels for most dendros (600ftcandles)

Of course one of the reasons for building this 4ft tall orchidarium was to fill it with orchids, however it now seems that I'm only be able to utilize the top 1ft of the tank. So I'm wondering, using a 125W CPF, what types of orchids can I grow that would be placed 3-4 ft from the light source? Why is there a large discrepancy of suggested illumination levels between different sites?

Thank you

Bosco