Hi! I bought a light meter this week and went round measuring light levels everywhere the same as u
my north facing window (where I keep my phals) also has a much lower light level than I originally thought - about 500fc! However my phals have always loved it there and bloom constantly
so there they will stay light or no light!
I also found that as light comes from all directions, how I turn the light meter in the window affects the reading, as well as how bright the day is and what time of day
I guess they just adapt as they are also supposed to be warm loving plants also, but uk temps are never that warm either
however what they do seem to like in my dingy window is the temp drop they get in the winter so they can slow down and store energy to bloom in the spring.
I would say if ur phals are happy where they are then don't worry too much about the light
King of Orchids had some links to phals growing wild and the light there is dime as they grow quite close to the forest floor way under the canopy.
If u do expand ur collection and use a brighter window keep a look out for pinky leaves and new leaves that are hard and stick up like a flag, or burnt patches as this means too much light.
If the new window is too bright u can always tone it down with a net to defuse the light