What does a light meter look for exactly, fluorescent related?

I have recently acquired a simple light meter designed for gardening. I don't understand why it reads the way it does though under different lighting conditions. LEDs and fluorescent lights don't seem to register on it unless it is right next to the bulb while laser pointer sends the meter off the scale as does a low powered halogen flashlight. The only readings that vary across a wider range are from standard incandescent bulbs, those seem to "loose" less power with distance.





Can anyone explain why fluorescent lights don't register on the meter even when the visible light is 10x that of the regular bulb?

What does a light meter look for exactly, fluorescent related?
We have quite a variety here! Lets start with the light meter. They are designed to read lumens, which is the measurement of light! They are nothing more than a solar cell that develops a voltage when light is applied, and it is connected to a voltmeter which is calibrated to read lumens. When you say it is designed for gardening, my first thought is that it is set up to read high levels of light (sunlight), this could be why you are getting very low readings using artificial lighting. That being said, the potential variables we are dealing with here are things like, Flourescent- is it a 4' tube, 8' tube, the small ones like a 2' or 6" tubes? Just as there is a large variety of sizes, there is also a large variety of color outputs and intensities such as High Output (HO), Very High Output (VHO) and Super High Output (SHO) Warm White , Cool White, they even measurte them in degrees Kelvin!4100K, 3200K, etc. For sake of arguement, I am going to assume you are using a 4' 2-lamp Shop Lite. Although this will put out more light (lumens) than lets say a 100-Watt Incandescent lamp, you are reading higher levels from the 100-Watt lamp beecause it is coming from a more concentrated source vs. the span of a 4'-Shop lamp! Also, the type of reflector you have on the fixture will change the readings. Lets say a drop light, this is directional due to the shade or reflector it has. A 4'-Shop Lite with nothing to direct the light at your meter sends the light in all directions vs the Drop light that has focused the light in one direction. I hope this has somewhat helped you???


PS: If you are growing plants indoors that maybe you don't want others to know about? Use an HID (High Intensity Dishcharge) Fixture specifically a Metal-Halide unit! It reproduces every spectrum of sun light except one band, that is why it is more white than regular sun light. Also, it puts out about 100-times more light, lasts 20 times longer than regular lights and also is 20 times cheaper to run!!!! GOOD GROWIN!!!
Reply:This answer completely fails to account for the fact that an incandescent light registers high on the meter but a fluorescent does not. While this answer may apply to photographic meters it obviously doesn't apply to gardening oriented models. Report Abuse

Reply:I apologize for not watching to see if you added info! Send me an e-mail, I will try to help!!!!!! Report Abuse

Reply:It only can register the amount of light that strikes the photo cell. A laser concentrates light in one spot. Fluorescent and some other lights spread light in all directions and the amount in one spot is not nigh.





The meter can only read the light that strikes the cell and it does that very well.