Light Meter

[grandmapenguin]

I bought a light meter since I have acquired more than one variety of Orchids. I just wanted to be sure they are getting the right amount of light. Now I have to learn how to read the meter. Is there anywhere I can find a chart of light needs for each type of Orchid?
Terry

[snowballsarebad]

A lot of the orchid books have this information in them, but other than that, I'm not sure.

[digitalgate]

plenty of information on the net.

Here what i remember
Phalaenospsis 750 lux (or you can use foot candle) to 3500
Vanda (include Rhynchostylis) from 3000 to full sun
Dendrobium from 4000 to to 5000 full sun

Some species like Rhynchostylis and Dendrobium maximum light is only 4000fc SO you
have to understand the plant before you decide on a number. but to make it easier
put all plant (except Prap and Phalaenospsis ) under 5000fc

Post your plant here and we can tell you what it need.

[grandmapenguin]

I have a Paph, Oncidium Twinkle Red, and a Cattleyaall on one table about 2 feet from an east window.

Then I have four under a floor lamp in front of a somewhat shaded west window.
These four are Tulumnia, Oncidium,and 2 Ascofinetia.
I bought the light meter to check exactly what kind of light I am getting; but really have to find someone to show me how to read it. The instructions are as clear as mud.
Thank you.

[digitalgate]

Oncidium max 6000 foot candle or 60000lux
Cattleya max 7000 footcandle or 70000lux
what type of light meter do you have. a brand and a model number would be very helpful

[jerrymeola]

You conditions are probably around 800-1500 foot candles, but I have metered bright rooms and found them lower than 600.

You said you bought a light meter but it may not have a reading for foot candles. Is it a photographic meter or one made for plants? The lower priced ones for plants are usually idiot meters - bad-poor-good type readings.

If it does not have a lux (foot candle) dial then use the settings from the chart in this thread. Measuring light levels with an SLR camera

Since it is a light meter not a camera you only need to set the ASA value and read the speed and F stop from the dial as if you were taking a photo. Then find the light value from the chart.

[PhalPal]

I bought a light meter a while back and the instructions were completely useless too. There was a LOT lost in translation and some of it was actually funny! I can take pity on you for having experienced this myself.

Digi you might want to check your conversions of foot candles to lux.......

[grandmapenguin]

Thanks PhalPal I feel like an idiot for having bought it. I should have checked with you guys first. It is a Cheapie $20 no name bought on E-Bay. It just says Digital LUX Meter.
When I turn it on and select 2000 I am getting 72 Lux. Great what does that mean????
If I set it on 20000 which is a x10 I get a reading of 7 Lux. Instructions are useless.
Hate to send it back by the time I pay postage it wouldn't be worth it.
I do thank Jerrry for the thread on Measuring Light Levels. i have to read up on my Camera to see if I can do the white papertest he talks about. Thank you everyone for your help.

[digitalgate]

you are fine. The thing is working just fine. when you select 2000 you select a mode that
can maximum read 2000 , once you exceed that value,it will display 0 or 1. when it is 72lux
it mean you have 72 lux. when you switch to 20000, you get 7 which is 7x10 =70 lux. It is
as simple as that. So give me the reading on your light meter and i tell you if it is enough for plant.

Here what you need to achieve , select 20000. move the plant to a spot that read somewhere around 500 for a 5000 lux plant. it is that simple.
Notice that you need to take different reading from morning to noon , afternoon, evening. it is to give you a gauge of rise and fall of light in your area. To calibrate
your light meter. Put light meter in full sun in the hot afternoon sun , it should read
1000 which is 10000lux for full sun. So any reading for 500 will be good for most orchid.
smaller number will be for low light orchids. Happy growing!

[patticake]

I would use a compact fluorescent bulb in your floor lamp if you haven't already. (the daylight wide spectrum). The incandescent bulbs don't do much for growth.

[Brooke]

Grandmapeguien I have a light meter that has both lux and fc readings but I never use the lux so I can't give you a comparison. Later today I can give you the lux reading to check your grow area if you want me to compare.

In the past I have done fc readings in my ESE window and find that two feet back from a double pane window with a screen is about 600 fc as compared to the window ledge which was 2000 fc.

Brooke

[grandmapenguin]

Thank you Brooke I am getting a feel now reading the posts I have been getting. I am looking forward to your posting of this information.
I made up a cheat sheet since I am a Newbie and getting older so I don't always remember like I used to. I listed each type of Orchid and it's likes and dislikes and light requirements etc. This has really helped me not to have to dig through tons of information. I probably should mention this on a new thread for Newbies. Do you think??
Terry

[dejpep]

This is a chart for a light ranges for orchids in foot-candles. I took this picture from the orchid book that I have. I hope it will help you out. At least you can figure out which orchids like more light and which less. Good luck.

[jerrymeola]

Digitalgate gave a good description of how the light meter works as regards to the 2000 to 20,000 difference.

What I am not sure about is if the 2000 reading is a 2000 to 1 ratio. That would make your lux 2000 x 72 or 144,000 lux which is equivalent to 13000 foot candles. That would be bright sun. If you were not in bright sun than the multiplier is different. Consider bright sun to be 10,000 to 13,000 and work from that as a beginning.

You can convert lux to foot candles at Foot-Candles to Lux Conversion Calculator roughly it is about 1/11th of the lux reading or for growing orchids using a 10-1 conversion is close enough.

You should look to see if you have a dial range that does not make you multiply.

[Brooke]

Divide your lux reading by 11.7 and it will give you the foot candle equivilency.

Brooke

[digitalgate]

grandmapenguin. is it easier now?

[PhalPal]

Originally Posted by jerrymeola

You can convert lux to foot candles at Foot-Candles to Lux Conversion Calculator roughly it is about 1/11th of the lux reading or for growing orchids using a 10-1 conversion is close enough.

Excellent Jerry; I think this is what she needed most.

When the settings change on a light meter it is basically moving the decimal point either higher or lower to give you a more accurate reading. It helps greatly if you first have a basic idea of what reading you should be expecting. The chart above can help you with this.

[grandmapenguin]

You all have been so helpful yes, it is getting much easier. I couldn't copy the chart that was posted so I just hand copied it. This was definately what I was looking for. Thank you all again; so much.
Terry