How long to give optimal light exposure?

[Flatland2D]

I'm still relatively new to orchids. I've been growing a phal stone dance and miltassia shelob webmaster for five months. I've also picked up two more NOID phals from Lowes and Walmart in that time, and yesterday I got my first online order from Oak Hill.

What I'm wondering is, how long do I need to give each orchid its recommended light exposure? Right now, every orchid I have sits on a desk in front of a south facing winding. Between tweaking the blinds, distance from window, and position around the window, I can pretty well fine tune lighting requirements (intensity and duration) for the different things I'm growing. However, that place is starting to get a little crowded and I'm thinking of moving some to hanging to the side of a west facing window.

The problem is, east and west windows only get light for a couple hours a day, whereas my south window gets light for most of the day. I've been using my camera to measure light levels and have been a little surprised by how much light is needed. My west window at midday with the sun on the south side of the house gets about 500 foot candles. It might go up to around 1500 later in the day, but the sun's intensity is less at that time (south window gets around 2000 to 2500 at its peak), and it only lasts for a couple of hours. Is this enough light for an orchid requiring 1000 to 1500 foot candles? I'm thinking about moving a phal and a paph here. Thanks for any help.