Cattleyas need lots of light...no lower than 2500 candles for most hybrids and can be as high as 4500 candles for species.
The light generally needs to be indirect as direct light heats the leaves which will burn them.
During the summer, in Pennsylvania, I am using 40% shade cloth over glass. That remains to be seen if it's enough. Over winter, I use 10%.
That said, I don't have my 40% up yet
My plants are looking like they have a bit too much sun (I will be putting up the new cloth this coming w/e).
Furthermore, some of the plants are throwing buds without sheaths lol. Not sure what to make of that!
Air movement is key as well if it's bright...you don't want the leaves to heat up. And even with indirect light, they can do so.