Determining lighting intensity under fluro tubes for phalaenopsis

[Magnus A]

Originally Posted by camille1585

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!

Been there Camille!
Have fought numerous battles about minor issues while major one's have been ignored and waved of. I am soo glad I left academia !

Though as a scientist, your work sounds interesting but that is not for this thread to discuss. Maybe we will meat in a distant futere and discuss science, life and orchids


Sorry OzPhal that we hijacked your thread....

[billc]

The poor man's light meter for phals is place your hand about a foot above the leaves. If you have a sharp shadow it's too bright. If the shadow is blurred or indistinct you should be ok.

Bill

[OzPhal]

Thanks Camille & Magnus,

I followed the protocol on Rays page and ended up with about 1,345 lux or 125 foot candles at approximate leaf height - some info that I've read suggest I should be looking at about 10 times that light? i.e. around 1,000 - 1,500 foot candles? any thoughts?

[Magnus A]

The value you found is maximun values during the day in one wild habitat. This does not reflect the overall light the plants need. during mornings and afternoons wild plants recive much less light.

You will give a constant light flux during the hole day. You should think in terms of total light per day and not maximum light at one instance.

/M

[OzPhal]

Originally Posted by Magnus A

The value you found is maximun values during the day in one wild habitat. This does not reflect the overall light the plants need. during mornings and afternoons wild plants recive much less light.

You will give a constant light flux during the hole day. You should think in terms of total light per day and not maximum light at one instance.

/M

Thanks Magnus for your feedback, that figure i quoted is the maximum, and consistent value, of light received throughout a 12hr period as the growth chambers are environmentally controlled - the lights are simply on/off - there is no dawn/midday/dusk etc

[Magnus A]

I would say that 1350 lux is on the low side. Most low light orchids do well under 5000 lux under constant conditions in a growth cabinet.

It would though still be relevant to know the relative geometrical placement of the plants and the light tubes and if there are reflectors.

The SLR light meter test demand god reflextion and that mean that if the tubes are placed far apart you practically only measure the light from one tube.

/M

[camille1585]

I'm thinking that the camera meter was way off. I looked back at the first post for the lighting specs, and it's fairly similar to one of my lights. With that, I can grow and bloom Phals that are about 15-20cm away from the lights. I know that it's hard to compare different lights..
Do you know how old the tubes are? As tubes age, light levels drop drastically. Any older than 2 years, and the tubes are giving out much less than the original light output, even if it doesn't look like that to the naked eye.

[GardenTheater]

Originally Posted by billc

The poor man's light meter for phals is place your hand about a foot above the leaves. If you have a sharp shadow it's too bright. If the shadow is blurred or indistinct you should be ok.

Bill

Thanks for simple option. I was doing the SLR camera calculations and this is much faster.

[Magnus A]

Originally Posted by billc
The poor man's light meter for phals is place your hand about a foot above the leaves. If you have a sharp shadow it's too bright. If the shadow is blurred or indistinct you should be ok.

Bill

Originally Posted by GardenTheater

Thanks for simple option. I was doing the SLR camera calculations and this is much faster.

The problem with this hand method is that you get different results depending on your light source. If you have diffuse light from a large light panel (a couple of long fluorescent light tubes) you never get a sharp shadow. While if you have only one very strong point source, you always get a sharp shadow...

The error due to your light source will be huge and render the method useless without a reference for Bills setup!


Magnus

[GardenTheater]

Originally Posted by Magnus A

The problem with this hand method is that you get different results depending on your light source. If you have diffuse light from a large light panel (a couple of long fluorescent light tubes) you never get a sharp shadow. While if you have only one very strong point source, you always get a sharp shadow...

The error due to your light source will be huge and render the method useless without a reference for Bills setup!


Magnus

My light source is the sun through various windows in my home. Windows are all the same brand and age. Do you think the hand shadows will work in my situation?