Lighting Help

[alanbar]

I am thinking of buying a hand held light meter. I have read about using the "hand and shadow" method, but i would like to get something that is more precise. Does anyone use a meter? I would also like to avoid spending too much $$$ on it.
I have been about the Photone app. It appears that it give multiple light measurements that specifically good for plants. Does anyone know how well it works and if it is very complicated to learn how to use it?

[Roberta]

When you think of being "precise" remember that light intensity is only one factor. There's light duration, and also a natural variation of light over the course of the day (and the seasons) that affect what a particular plant receives and/or "wants" to receive. So, for instance, Phalaenopsis are low-light plants, but want light duration of about 12 hours a day (since they come from near the equator where days and nights are nearly equal, but they grow in the shade).

So... not something that can be reduced to a single number. If you choose a light intensity based on what you read about for a particular plant, you are likely to give it too much since the numbers are usually for the maximum brightness, but in a natural setting they get that intensity for only a few hours. Best to err on the low side with light, increase gradually if needed. (Too little and they may not bloom or grow as well, too much can burn very quickly and be devastating) And observe your plants... see how they are responding. Make any changes gently a bit at a time.

[alanbar]

Thanks, Roberta. That was a very sensible reply. I tend to obsess over the amount of light and the quality of light. Living in an apartment I have to adjust where the plants are in relation to our windows and which plants go under the table top lED stands.

[Dimples]

I use this one and it’s quite reliable.

---------- Post added at 03:34 PM ---------- Previous post was at 03:24 PM ----------

I took multiple measurements by each area of plants over the course of a day to track the change in light/foot candles throughout the day. Winter is the lowest light so that’s what I focused on. I learned that I needed to add supplemental lighting to my east facing window grouping in the winter. They’d get 2,500fc for a few hours in the morning then zip-zero (<100fc) for the rest of the day. That explained why they did so poorly over the first winter in this house. Late Spring-Fall the light is bright enough all day and no extra light is needed.

I also learned that adding white sheer curtains to the south windows dramatically improved the light distribution in the room and eliminated the risk of burning/bleaching so I can put my phals in a much better spot without worrying. My other houseplants are a lot happier too.

[camille1585]

Originally Posted by alanbar

I am thinking of buying a hand held light meter. I have read about using the "hand and shadow" method, but i would like to get something that is more precise. Does anyone use a meter? I would also like to avoid spending too much $$$ on it.
I have been about the Photone app. It appears that it give multiple light measurements that specifically good for plants. Does anyone know how well it works and if it is very complicated to learn how to use it?

If you are using Photone on a compatible device which they have calibrated, then yes, it is fairly accurate. I have it on my iphone and I tested it alongside a professional, calibrated quantum spectrometer that we have at work and I was getting readings within 10-15% of the pro device. I would consider that quite good considering that we use devices from 2 different companies and despite regular calibration there is an 8-10% between them. Note that I only tested it under single source Red/Blue LED lights where I work and measuring in micromol/m2/sec.

But like Roberta points up, knowing the light intensity is only a small part of the equation! I did like being able to measure the light intensity because I had absolutely no idea how much my supplemental lights were adding. And with this information I could safely exclude 'not enough light' as the reason some plants weren't blooming.

[skirincich]

The Photon app used with a light diffuser gives pretty good numbers for LED grow lights. I would not use the hand-shadow technique since I believe that plants can handle more light since the LED lights put out less infrared (heat) light and therefore heat the leaves less than the sun.

[estación seca]

The hand shadow technique is for natural light, usually through a window. Glass blocks most infrared. More light than necessary isn't always a good idea. It uses more electricity. Some plants, like Phals, don't flower as well with excessive light.

[nhbeek]

Originally Posted by estación seca

The hand shadow technique is for natural light, usually through a window. Glass blocks most infrared. More light than necessary isn't always a good idea. It uses more electricity. Some plants, like Phals, don't flower as well with excessive light.

The new horticultural LEDs are great products but not designed for the cultivation of orchids...lol

It is very possible to stunt / stress even the highest light cattleyas and vandas with them (> 12 hour day + light too close).

The advantage of these lights is you can hang them very high above your plants, so huge cattleyas or vandas wont need to be awkwardly smashed up against the lights.

[itilien]

The hand shadow technique is absolutely meaningless when the plants are lighten by artificial lights, because the shadow depends only on the angular size of the light source viewed from the illuminated point. If you have two light sources that emit light with the same intensity, and one is a small bulb, the other one is a flat panel with big area, the bulb will give sharp and strong shadows and the panel will give very soft shadows. Also the sharpness of the shadow will depend on the distance relation between the object in shadow, the object that makes the shadow and the light source.

[MateoinLosAngeles]

I use the Photone app and there are professionals on Youtube comparing it with quantum readers. The photone seems to do pretty good on those tests.

However, I don't aim for precision, what I aim for is to have a better understanding of the actual light my plants are receiving. I am a photographer and have North-facing windows which work great for photography but are not enough for most plants. So I supplement my natural light with LEDs. I prefer to err on the side of providing less light and add from there.