Light level is one of the truly important care parameters you need to understand for each of your orchids. What is too much for one can be too little for another, and vice versa.
Phalaenopsis is one of one of the most common orchids found in the home. They are sold everywhere. In fact, if a store (say, a supermarket) sells only one type of orchid, there’s a 99% chance it will be the Phalaenopsis, also known as a “Moth Orchid.” Why? They are easy to mass produce using meristem propagation so they are raised in huge quantities. There are greenhouse businesses with literally acres of Phals. being grown for these markets.
As a result, they are inexpensive (relatively speaking), with tremendous varieties of colors and flower sizes. They are relatively easy to raise (see Phalaenopsis under Orchids). They need light, but not harsh light. Until you have a little experience caring for Phals, just don’t put them in direct sun (that’s the most typical recommendation – no direct sun). That’s actually not totally correct. There is direct sun and there is direct sun. I keep a very large quantity of orchids on a three tier rack in front of a huge set of windows. Each tier is further from the window than the previous one, from the top (closest to the glass) to the lowest (furthest from the glass). The window faces east. So it gets morning sun. Morning sun is the least harsh. The overhang of the roof prevents anything on the shelf from getting the most brutal direct hot summer sun – in fact, no direct sun in the summer past about 11 AM. And the eastern sunlight is downright gentle in the winter. I routinely keep Phals on the lower level. There are three ways the light level is reduced. First, it’s morning sun only. Second, the bottom tier is furthest from the glass (the intensity of light drops off DRAMATICALLY as distance from the window increases). And third, what sunlight does come in the window is filtered through two other shelfs-full of orchids before any dappled light gets to the Phals. In reality, Phals are VERY easy to adjust the light level for. Why? They tell you when they get too much light! See the reddish cast starting on the edges of this otherwise very healthy Phal leaf? That’s the result of too much light. Simply reposition it to someplace with lower light, even if that change is as subtle as simply moving it further from the window.
The Cattleya orchids and and all of the crosses are a different story. They like high light, and that includes some direct sun. But there is direct sun, and there is direct sun. Have you ever left something sensitive in direct, hot, afternoon summer sun VERY close to the glass and it got ruined? Not only was the sun too intense, it also generates a surprising amount of heat. You don’t want to do that even to the hardiest of orchids. But I have hardiest orchids a foot away from the glass with direct morning sun, and a little further from the glass with the more intense afternoon sun.
This cattleya (actually a Brassolaeliocattleya, or Blc. His Light x Hawaiian Lightning) loves high light. In this case, that slightly reddish cast is a good sign, not bad. It means it’s getting good light. This plant is relatively new to my collection, having been purchased in late summer 2016. As a result, you can see a distinct difference between the older leaves and the newer, reddish leaves. The older leaves still have the residue on them from the spraying that is invariably necessary for pest and disease control in truly large operations. You simply cannot afford to have any sort of infestation start when you are dealing with entire greenhouses and acres of plants. If you have read much of this website, you’ll know that as a matter of personal preference and practice, I generally avoid getting water on my plants when I water the bark and/or moss and roots thoroughly. And I don’t use harsh chemicals, including insecticides as anything but an absolute, desperation last-resort. But I’m not opposed to having passive insecticide hang around when it’s provided on new plants to my collection. Sooner or later they will have to be washed (some day, some time most of them will get a little scale, perhaps a few aphids…)
I know, they get rained on in their natural habitat. But my “orchid room” is not their natural habitat. And I like to keep things dry to avoid mold and other “inconveniences.” I’m not afraid to spray a mist on orchids if I think they could benefit from humidity, but since I run large humidifiers all winter and have a relatively humid climate in the summer, that’s not really a problem either. The only orchids I keep are the ones that will do well in “normal” humidity – say, 40% – 70% give or take. I don’t know of any orchids that like desert dryness, and I simply don’t keep orchids that need continuous 80% or 90% humidity to do well. But I”m getting off the subject of light.
You should get the “picture” (pun intended) from these two photos. Most orchids you’re likely to successfully keep are going to within this range (from the lowest levels represented by the Phals. and the highest levels represented by the Cattleyas. Read up on each orchid on this site or others to get a general idea of the appropriate light level for each genus, and approximate it when you bring a new plant into your home. Observe it carefully but if you follow the general perimeters, you shouldn’t be far off. General rules: No truly harsh, direct summer sun close to the glass and low light doesn’t mean in a closet! Between those extremes you’ll find a good home for most orchids. Just read up on them!