I got a light meter, and am surprised at the readings
 

I bought an inexpensive lux meter the other day to finally have a clearer grasp of how much light my orchids were getting.

Before I bought the thing, I had guessed that my plants were receiving an amount of light on the low end of their requirements, but still within an acceptable range. Boy was I wrong!

It turns out they are receiving more like one tenth of their requirements. This is blowing my mind a bit...shouldn't they be dead at this point?

The paph/phals are receiving around 1169 lux, as shown here...much less than their minimum light requirements of 10,000-15,000 lux.
http://www.orchidboard.com/community...m/IMGP0400.jpg

Not much better for this oncidium, which is receiving 2,290 lux (the meter is in x10 mode here) instead of the recommended 20,000.
http://www.orchidboard.com/community...m/IMGP0399.jpg

I must be missing something because this just doesn't seem right.

My sources for light requirements are the AOS culture sheets. Lux are roughly converted into footcandles by dividing by ten.

More details available in my blog entry.

Amazing, isn't it?!

I remember when I first got my light meter (several years ago)...I was shocked at how little light the plants were getting. What seems so bright to our eyes...well...our eyes are virtually worthless gauges of light requirements for plants. My set up today...w/all the lights...glows like some kind of spaceship when people look at my house after dark. For those who first walk into the space...they feel like they need sunglasses. Bright would be an understatement.

As for how your plants are still alive...many plants can survive for years under less than ideal light but you won't get them to bloom.

A light meter is an invaluable tool in any orchid grower's arsenal. You won't regret that purchase! Getting the lighting right...I foresee LOTS of blooms in your future.

Just wait until you start testing for TDS and PH. You'll be like a mad scientist.:)
If you plan on giving the plants more light, do it gradually or you will wind up like I did with a bunch of burned leaves. Not a pretty sight!

Bill

Lol. I am going to take a chill pill and let mother nature do her thang. Right now they're dealing with an 8-hour photoperiod and the sun at a very low angle. In six months, the days will be 16 hours long and sunlight will be pouring in those windows. Can't wait to take some light meter readings then!

"If you plan on giving the plants more light, do it gradually or you will wind up like I did with a bunch of burned leaves. Not a pretty sight!"

So this is why i manage to scorch them in the summer. I guess when you add up all the window obstructions and overcast days they are getting much less light than we think.

But then some plants can be surprising. I gave a coworkers a little Oncidium (One of the Twinkle parents) a few years ago. It manages to bloom with office lighting and a northern window exposure.

I also have a very basic (inexpensive) light meter and like you, when I bought it, my readings showed up very low. Granted, I was testing the light levels underneath fluorescent lights, which those meters are apparently not that great at measuring. Either way, the readings were showing light output was about 1/4 - 1/2 of recommended minimums for my plants, but I knew that was wrong.

Sometimes just looking at your plants will give you a better idea of whether they're in proper lighting conditions, though the effects might take longer to show up. For instance, despite the low light readings, I could tell that some of my plants were in the high level of their light requirements because they'd develop red pigments/coloration in the leaves, or they were producing light green leaves (yellow/lime colored). Plants that aren't getting enough light may stop growing new leaves or slow way down, and the foliage will become dark green.

I think as others have pointed out, it's fall/winter in the northern hemisphere, you're not only getting a reduced number of hours of natural light, you're also getting reduced strength (generally). But also, the amount of light is going to vary day to day depending on cloud cover and other factors and it's going to vary hour by hour.

I tend by nature to be technically oriented so I have several light meters of various kinds and I use them a lot, but I think there is still a lot of art as well as science to measuring light in a growing area. There is duration as well as intensity, you've probably noticed that your readings vary wildly depending on how you orient the sensor to the window, and as others have pointed out intensity will vary a lot with the time of year, time of day, weather, etc.

If your plants are growing and blooming well then I wouldn't rush to change anything no matter what the meter says. If they could be blooming better then I'd increase the light somewhat, not all at once but gradually as other posters have said, watching carefully for any sign that the plant isn't happy.

We try to take lots of readings with our meters, to get an idea how the intensity in different spots varies during the day, and over time and seasons. We got some unexpected results, and we're still learning.

Steve

Ok well I may be crazy because I've just made this thread into a video. I hope all the information in it is correct!!

That is crazy!!! Are you sure the digits are correct? lol

but seriously, your plants look all perfectly fine to me.
How long have you have that paph and phal in that location??

I doubt those plants will look that healthy and flower normally if the light they are getting is indeed one tenth of what they need.

---------- Post added at 05:06 PM ---------- Previous post was at 05:02 PM ----------

Ok, I just watched your video.
I don't use light meter as my plants all grow fine.

Judging by the brightness of your growing area by the window, whatever the machine says, it looks bright enough for them to me.

Maybe you measured it on a very cloudy day? It looks rather dark, but then I see some other scenes where the window sill appears much brighter and then I also see a scene with sun light shines in through the window.

Hey NYOM, you're right, I did measure on a cloudy day. Today was sunny and the reading got up to 3000 for the phal/paph and up to 3800 for the oncidium. Still below their minimums, though!

The pic with the sunlight shining in was taken in July. I included it to illustrate the range of lighting conditions that exist over the course of a year. I'll be sure to post those light readings when the seasons change!

I don't use a light meter, either. I pretty much have natural light figured out after all the years I've been growing plants. For those that need full sun, I know what they can tolerate indoors with minimum stress.
Now that I bought my first light, though, I find I am learning all over again. :|

Current light meters (and light meter smartphone apps) are too precise for our application. These devices are made for professional photographers, who need to adjust exposure and flash settings at the aperture, so they need point precision.

What we need is a meter that captures light over a much larger area, and we're not likely to find one.

I agree. I know there are numerous ways of doing things... Some like to follow instructions to the letter and measure everything with sophysticated devices. Others use their senses, observations and experience. I know my plants are getting enough of sun light by observing their leaves color - light green and sometimes even being close to a sunburn if I don't use a sheer curtain.
And 80% of them are in spike and growing rapidly.;)

Cambria, like you, my meter is either whacked out or my plants are getting WAY less light than they need. None of my phals have spiked and it is phal spiking season. Here is what I think I'm going to do: I have a huge bay window on the first floor that faces west, southwest, and northwest. I HATE the idea of putting racks of plants in front of it, blocking the light for ME, but I think that's what I'm going to do. I'm just tired of stressing about the light!

Freaking.Awesome.Video!!

:agree:

May I ask what program do you use for recording the videos before dowloading them to YouTube, and how do you add arrows, etc?

Thanks! Really enjoyed watching the seria! The shoe string to support the spike is ingenious! :biggrin:

Guys thank you so much for watching the vid! I'm trying to make a new one every week if you would like to keep checking in and see how my little green pets are doing ;) Wild Orchid, the program I use for editing is Pinnacle Studio 15.

Back to the light issue, after some thought, I don't doubt my light meter's readings. I live at 48.5°N, right now the sun is only up for 8 hours, and is so low in the sky that it never clears the surrounding buildings, which means not a single ray of sunshine enters my windows from November to February.

My plants are alive, and even growing a teeny tiny bit, but the phals' spikes are just pitiful. They've stopped growing at less than 10 inches, and I think I'll be lucky to get more than a couple flowers on each one.

Still, this is very interesting to me in terms of seeing what happens under such conditions!

I just got my light meter and tested the light and received the same results but there is new growth on my African violets. I guess I have to wait for a sunny day to try again.

The light meter app I use on my iPhone requires that I point the meter at a white piece of paper to capture most of the reflected light. Plant leaves absorb light and reduce the reading. White gives you a more realistic number.

I use the meter to find new growing areas in my house and outdoors. After the plant has been in the space for several months, I look at the color of the leaves and how the plant is doing.

Enjoyed your video!

Wasn't surprised that you were surprised. ;)

I have often gone round and round with folks (on various plant forums -- not here but rather typically terrarium/vivarium related) who drive me nuts insisting that they "know" the plants are getting enough light because they can "see" there is plenty of light. Trying to get through to them that our eyes require far less light to see by than a plant requires for photosynthesis can be down right aggravating.

That aside, it is amazing how many plants can hang in there with less than optimal conditions.



New growth can and will occur even with poor lighting, SF. With your AV the thing will be for you to look at the growth as it grows and matures. The leaves of an AV should form a rather flattish, fairly tight rosette if the lighting is optimal. If the petioles are really long and the leaves are reaching up towards the light, you light is below par.

I knew the task lamp I bought was bright it's producing almost a 1000 footcandles. Crazy I found an app for my phone and it seems to be working

Actually, 1,000 footcandles is pretty low. To give you an example, good light for phalaenopsis is in the range of 1,500-2,500 footcandles

why can't everyone agree on the same range? It's gets confusing after a while as to how much light to give. :tapfoot:


I've gotten answers between 500 to 2000 it's frustrating

Sorry, I replied to that via Tapatalk and all that showed up was part of one of your posts, I didn't see all the other replied.

People all can't agree on a range because for each orchid grower there is a different method to growing. 1,00-2,500 is an optimal range, but that's not to say that given the right circumstances (such as increased humidity and airflow to the accompany higher light levels) Phalaenopsis can't do well under other light levels 1,00-2,500 is just what is optimal.

Right, i mean mine has five buds getting ready to open and its been getting 150-300 fc since october. More light, more flowers, i guess.

I grow under lights in my basement in the winter. I have a 400 w HPS and a 4 x 2' T5 setup that run for 12-13 hrs. My phals read about 500 fc, which is well below the reccomended 1000-2000 fc. They don't stop blooming! My multifloral paphs read about 1000 fc, which is well below the recommended 2000-3000 fc, and the leaves of my Lady Isabel are nearing sunburn. Point being- I don't trust my light meter.

When I got my light meter I was summering my plants outside in a shadehouse and was disappointed at the rate of growth (or lack thereof). As it turned out 50% shade plus 80% shade plus almost continual tree shade throughout the day was just not enough light. The light meter worked great for this application and confirmed my hypothesisat first I removed the 50% cloth for a few days, then the 50 went back on and the 80% came off. It was amazing how my plants took off.

I had heard the warnings about using light meters in home for both under lights and windowsill applications. Somehow my plants survived last winter, and the fc reading of my last light setup was somewhere around 100 fc. Needless to say my plants didn't thrive. But I still managed to bloom a paph roth...

Let the leaves tell you what your plants need. Dark green misshapen leaves are a sure sign of too little light, I know this from experience. Bleached out yellow leaves are a sure sign of high light, I know this from experience. And while many factors play in to those facts, decent temp/humidity/water/fert, once your plants adjust to your conditions it's amazing how tolerant they are!

It's so true. Three months of short, dark, cold days and still I'm going to have some flowers. Orchids are awesome :)

You are probably mixing up light values!

The very high values recommended is often the maximum light intensity at mid day at the natural habitat, close to the equator and that has very little to do with the plants need !

You have to consider the accumulated light energy the plants get over the day and if you use artificial light you have a constant flux of light over the day that is NEVER present in nature!


If those very high light values were correct it would be impossibly to grow orchids indoors in terrariums! And it is not!

Today the angle of the sun has finally reached the point to where direct light made it through the windows. This is the first ray of light since the beginning of November.

Light meter readings have skyrocketed to 4000-5000 lux/400-500 footcandles on the orchids and over 8000 lux/800 fc in the direct light.

I feel that I can safely say that the dark period is over! Bring on the growth, bring on the light!

http://farm4.staticflickr.com/3817/1...3f6e8320be.jpg

I think that sometimes orchids can get by just fine on less light than recommended. My neighbour has a neglected paph that is stuck between 2 huge jade plants in a North window. It is now in spike.

I agree, some people are not interpreting the recommended intensity appropriately. This may be an interesting read. http://www.aos.org/Default.aspx?id=516 The title of this article seems irrelevant, but it clarifies the difference between the sun and continuous source

That was...some science right there. So I should be looking at 50 to 70 percent roughly of the maximum recommended levels? Either way, my experience this winter has shown me that at less than 2000 lux and a photoperiod of less than 8 hours, my phals will spike and flower, although the flower count is low.

Your plants are lush and dark green. I was told that's a sign that they aren't really getting enough light.

Plants and humans use light differently. Plants photosynthasis has do with color wavelengths, not light intensity. Foot candle light meters are for photography.

Plants photosynthasise using the orange and red spectrum, at about 600 to 700 kelvin.


The human eye can only see about 550.

I kind of think when people say Light, they are all talking about different things.