measuring light levels.
 

Took me a while to work out what the question is I wanted to ask.

I'm trying to establish a good place for my Phals, in the 1,000 to 2,000 fc range.

Now the problem is for me in measuring the light levels. In the full daylight it's 9 to 10,000 fc. In the full shade, no matter how bright, it's only 500. Ok, that's simple with my new toy, a light meter.

However, the dappled shade is a problem. It consists of bits of shade which show 500, but then if you move it so that the detector is in a brighter area, the reading is much higher.

So how do I estimate what the light levels there are please?

If you had a good light meter it would have come with a dome attachment that averaged the light hitting the cell. You don't need a light meter. Just hold you hand 1 foot above the place you want to measure. If the edge of the shadow cast by your hand has a 1" to 2" transition from shadow to light it is perfect for phals. Phals aren't that finicky. They just don't like it so bright that it scorches the leaf.

Agreed. If you're concerned about light levels, stressing about how to measure it accurately, and you're not a commercial grower -- I almost feel like you're doing it wrong in terms of phals.

Be patient, let the plants guide you as far as what they want. Most of the inexpensive hobby-type light meters are worthless for a lot of growing situations. They don't do a good job of measuring the spectrums of light that plants crave, they don't very accurately register light levels from artificial sources, and they are incapable of accurately measuring the average light levels of a shady outdoor situation where the angle of the sun and lots of other factors would change throughout the day.

OK, thanks for that. So they aren't bothered by a patch of light 2" in diam coming thru and shining full on the leaves, but a patch of light that was as big as your hand would be a problem. Is that a fair summation?

---------- Post added at 12:57 PM ---------- Previous post was at 12:48 PM ----------

Well, you have to remember that I lack the experience to be able to look at a site and go Yes/No. I'm not trying to be anal and achieve the perfect light level, were I doing that, as you say, I might as well set up a commercial type set up, and that's not what I want. However, I don't want to stick my plants where it is hopelessly low light level, wait a year and get no blooms, try another site and endure another barren year. I'm not so young that I have that sort of time ahead of me.

Equally, deep fried Phal is not a dish I wish to sample.

So, while the light meter may be a waste of time and money, it has shown me where NOT to put the plants, so that is a positive point for it.

Thanks for both of you taking the trouble to expain carefully and helpfully. It's bad enough being a noob without also having someone laugh at you or be unhelpful. Or for that matter having no where to turn to for advice.

Virtually any light level apart from full sunlight is fine for phals. They will take from pretty deep shade up to nearly full sunlight. That fist size patch of full sunlight is probably smaller than you think. Light spreads out at a ratio of 4 times the initial diameter of the aperture of the hole. It may look bright but it's intensity is diminished quite a bit the farther the object is from the hole making it. And light spots like this usually move fairly quickly across the scene.

They are right, listen to their advice....unless you have a lab or you want to have mass produced orchids in a large farm then a light meter comes in handy to achieve uniform growth....
Trust your instincts. Observe your orchids. You have pictures of healthy plants to compare them to and you will know if they have less or enough light....
you are in sunny Spain so you want your Phals outdoors under a tree with dappled leaves protecting them from burning.

---------- Post added at 02:36 AM ---------- Previous post was at 02:28 AM ----------

The sun's intensity outdoors is not constant. Light meters will never work outdoors for you because the intensity of the sun differs according to the cloud formation and the angle of the solstice. Photographers need light meters outdoors to adjust the camera ....what will you adjust? If so you will end up moving your pot every minute of the hour the clouds pass bye to achieve the perfect foot candle reading....

Again, I appreciate what you say, but I am not trying to achieve a lab like effect where everything is uniform. The meter has been useful in demonstrating where NOT to put them, because the light levels rule that area out. The last thing I want is to waste a year waiting for plants to bloom, when they can't.

---------- Post added at 03:01 AM ---------- Previous post was at 02:58 AM ----------

Ah yes, the good old inverse square law. I had forgotten that. Thanks.

They still grow and bloom better in the higher registers. I wish someone had more to say about "optimal" vs. " minimum".

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AOS has a lot to say about light levels for different orchids. Their culture sheets give good info about light levels. Just google AOS or American Orchid Society and go to culture sheets.

Small shafts of direct sunlight are not an issue, as they do not stay located on a single part of the plant - as the earth rotates, the spots "move", avoiding overheating of the tissues.

Be careful about AOS culture sheet light levels, as the numbers are recommended peak intensity levels seen in a day, and not the intensity it should see for the whole day. For windowsill and greenhouse growers, that's fine, but sometimes folks growing under lights "overdose" their plants by doing just that.