Determining lighting intensity under fluro tubes for phalaenopsis - Orchid Board

OzPhal · #1 07-04-2012, 10:19 PM

Hi Everybody,

I just have a quick question in regard lighting intensity and determining plant distance... I have a growth chamber at my work which I'm using to grow my Phalaenopsis species seedlings... the chamber is temperature, humidity and light controller - for growth I've got it set to a constant 28oC @ 80% humidity. There's two growth tubes in the chambers they're Osram L30W/865 tubes and the specs given for them are:

Colortone: Cool Daylight
CRI: 80
Initial Lumen: 1,825
Color Temperature: 6,500

Based on that data is it possible to calculate what sort of foot-candles i'm obtaining and what the ideal placement away from the tubes would be so as not to burn the plants?

zxyqu · #2 07-04-2012, 11:05 PM

Why not invest in a good light meter. They really help in the long run, and this would obviously be beneficial for your current setup (which sounds awesome and quite similar to my own!).

Magnus A · #3 07-05-2012, 02:40 AM

Or why not invest in a cheap light meter? You do not need a scientific valid value but a rough estimate.
And if you have a growth chamber with that control at your work, I would not be surpriced if there is a realy good light meter somewhere around!

And for your question. No it is not possibly from given data to calculate the light intensity at the plants. You need to have the geometry of the tubes and the growth chamber including plant position, placement of the tubes, information of reflectors and their reflectiv geometry. And still you get a rough estimate... Much better to have a cheap light meter.

It is no problem to calculate the intensity a certain distance from a single tube without reflectors when you have the output in lumen and the geometry of the tube. But geometry of the growth chamber and reflectors complicate things.

camille1585 · #4 07-05-2012, 03:25 AM

Magnus, we have about a dozen of such climate cells at work, plus 40 climate cabinets, but no light meter.... So it's not a given! I even have to bring my own thermometer from home if I have a doubt about the accuracy of the settings of the cell/cabinent I'm using. But I'm not allowed to put any of my own plants in them, nor in my greenhouse compartment.

OzPhal, if you have a dslr camera or advanced point n shoot, you can use the built in light meter on it, it gives a good ballpark figure. I'd have to look up the instructions again.

OzPhal · #5 07-06-2012, 03:52 PM

Hey Camille, thanks for your reply... You're right - we have some fancy equipment but you don't have a need for a light meter in a microbiology lab... If you could find any info on using a camera light meter that would be awesome! I have a Canon 7D in the lab...

camille1585 · #6 07-06-2012, 04:04 PM

I remembered that Ray has the info on his site. Light Intensity Measurement Take several measurements to make up for the lack of precision, and the average should give you a rough idea of the light levels in there...

Magnus A · #7 07-06-2012, 04:08 PM

Quote:

Originally Posted by camille1585

Magnus, we have about a dozen of such climate cells at work, plus 40 climate cabinets, but no light meter.... So it's not a given! I even have to bring my own thermometer from home if I have a doubt about the accuracy of the settings of the cell/cabinent I'm using. But I'm not allowed to put any of my own plants in them, nor in my greenhouse compartment.

OzPhal, if you have a dslr camera or advanced point n shoot, you can use the built in light meter on it, it gives a good ballpark figure. I'd have to look up the instructions again.

I know the feeling Camille! We had a growth room that was perfect for some of my orchids and only used to 25 % but i could not put anything in there! Though we had several light meters and also thermometers that was calibrated correctly! That was one of the things our professor was good at! To know your conditions.

OzPhal, for using a camera to messure light you can take a look at this page: Light Intensity Measurement

camille1585 · #8 07-06-2012, 04:17 PM

Quote:

Originally Posted by Magnus A

I know the feeling Camille! We had a growth room that was perfect for some of my orchids and only used to 25 % but i could not put anything in there! Though we had several light meters and also thermometers that was calibrated correctly! That was one of the things our professor was good at! To know your conditions.

I have an 18m² greenhouse compartment with MH lamps, misting system, automatic shade cloth, heating AND air conditioning systems, and I only use no more than half of it, for growing black mustard plants (for my experiments). The orchids would LOVE it in there! It's torture seeing all that beautiful empty bench space, while my orchids are on not so bright windowsill...

We have one fancy piece of equipement, a calibrated device that measures air speed, temp and humidity. But it's meant for the mosquito windtunnel, and kept locked up in a professor's office.

Magnus A · #9 07-06-2012, 04:24 PM

Camille, science is sometimes mysterious! You control small things in absurdum while other, bigger and more important factors are totaly ignored! I have been there and I do not like it...

camille1585 · #10 07-06-2012, 04:32 PM

The worst of it is, we're in plant science, but everyone is so focused on our area of research (plant-insect interactions) that there is zero thought for anything else. The slow growing cabbage plants are never fertilized and PhD students wonder why they are yellow. Or wonder why the plants are so leggy when grown in the lab, facing north. The list goes on.... And as you say, they are concerned by only minute details. "Oh no! There's ONE aphid on my plant, it's going to induce the defense system and ruin my experiments!!" Meanwhile, the plant is showing nutrient deficiency... Absurd!