What is Light Intensity?
In scientific terms, light intensity measures the wavelength-weighted power emitted by a specific light source. More simply put, intensity is an expression of the strength or amount of light produced by a light source.
Is Light Intensity the Same as Brightness?
While we tend to think of brightness when we talk about intensity, it’s not a good idea to use these terms interchangeably, especially in the context of plant cultivation.
There is such a thing as objective brightness—a quality of light that can be measured in quantitative terms. But when we talk about brightness, we’re often talking about how the human eye perceives light subjectively. Red and blue light appear quite dim to human eyes, but for plants, red and blue are the most photosynthetically active wavelengths on the light spectrum. Therefore, if you confuse “intensity” with “brightness,” your perception will cause you to favor lights that look powerful to you over lights that are powerful for your plants.