How much light is enough

[chubaroo13]

I am working on nursing a Phal back to life that a friend had bought in Hawaii. Being as I don't have a south facing window and it is fairly cold here in Ohio I built a small artificle greenhouse in my basement. I am able to control all the usual climate settings in it. Given this orchid hasn't had much care and was not kept in a window before I received it the other week, how much light should I give it this time of year to start?? I heard anywhere from 12-16 hours a day. The lighting is artificle 60W grow bulbs placed two feet above the plants. I keep a digital thermometer on the surface of the soil to make sure the leaves don't get too warm(no higher than 82 degrees is what I could best figure out from reading).

[Cynthia, Prescott, AZ]

While it is recoperating, long hours may give it more growth, but sooner or later you want the plant to get in sinc with the real seasons. So set the length of light-on to the normal day length plus and hour or so extra. Here is a chart for day length vs date vs latitude.
http://www.orchidculture.com/COD/daylength.html

[mayres]

I don't think two feet away is going to be NEARLY close enough for a 60W bulb. Test the light intensity with a camera and piece of pure white paper if you don't have access to a light meter (which most people obviously don't). If you have a camera with an auto aperture/shutter speed control setting - make sure your ASA is set at 25 and your shutter speed at 1/60th of a second. Point your camera at the paper and fill the viewfinder completely with the paper (careful not to block your light source!). The aperture your camera chooses will indicate the light intensity - f/2.8 = 200 footcandles, 4.0 - 375, 5.6 - 750, 8.0 - 1500, 11.0 - 2800. The point at which you get a F 8.0/1500 reading is about as close as you want to get for phals. If you can, let us know how close this is. I'm guessing it is going to be a lot closer than you think - I have my phals just inches from 40W fluorescents that are much more energy efficient in producing light from electricity. One problem with tungsten vs. fluorescents, besides poor light to energy consumption, is heat. Good luck - mike

[Cynthia, Prescott, AZ]

Hi Mike. For those like my self that have a digital camera that does not go below 100 ASA/ISO, here are the numbers for 1/500th second and 100 ASA/ISO: F/2.8 = 250fc, f/4.0=500fc, f/5.6=1000fc, f/8=2000fc, f/11=4000fc, f/16=8000fc. It looks like our data differs a little bit. Not sure why. I got this from a table that used to be on orchidlady.com, but it isn't there any more.

[mayres]

Cynthia - OK - since I do have access to a light meter I'll see if I can do the actual test (which I have only read about and like you recorded the numbers that someone else has determined). Nothing like having your own data instead of proliferating someone elses - that way I can take 100% credit for my own mistakes! :-) mike

[jerrymeola]

For a more full table of speed and light settings, here is my post from last year.

ASA and shutter speed are inversely equivalent. If you double ASA you halve the Shutter speed and it is exactly the same.

[jerrymeola]

For a more full table of speed and light settings, here is my post from last year.

Measuring light levels with an SLR camera

ASA and shutter speed are inversely equivalent. If you double ASA you halve the Shutter speed and it is exactly the same.