Does dimming your grow lights change the light spectrum?

[Rootsruler]

Someone on here had posted that dimming will change the light spectrum and you should run your lights at 100% to get the "full spectrum" lighting.

Not true.

Understanding LED Grow Lights: Power Needs and Spacing (ledlightexpert.com)

[golfnrl]

Thx for putting this up on the forum. Let's put that issue to bed. I asked HLG this specific question last year. 'Does dimming my lamp change the spectrum? I was told, "no, not enough to matter in agriculture". IDK if that is specific to HLG or not. But, I have adopted the mindset that dimming the light only affects intensity, not the light spectrum. My last auto grow the light never got above 5 clicks of 10 on the dial. Had the best harvest of my somewhat short auto grow experience. Because I harvested 8oz from one plant, I'm now convinced I can turn down the intensity w/o fear of limited or reduced yields.

I'm growing 4 sativa's that are vegging under the HLG Scorpion Rspec. The light is about 30" above the canopy at 2 clicks on the 10 click dial. Plants have tight node spacing, no light burns, no burnt tips, no heat issues. I'm using a Phantom PhotoBio light meter (recommended by someone on the forum) to measure umols. At that setting my plants are getting the right light in the recommended range for their stage of growth.

[SoOrbudgal]

Thanks for this post Rootsruler I totally agree with it.

[Mollisol]

That was a good article Rootsruler

[Bluey]

Dimming the light reduces its efficacy as most well made grow light/driver combinations are designed for maximum efficacy running at full power.

Lights that are most efficient at under full power are typically being over driven and result in shorter life.

[Rootsruler]

Dimming the light reduces its efficacy as most well made grow light/driver combinations are designed for maximum efficacy running at full power.

Lights that are most efficient at under full power are typically being over driven and result in shorter life.

Actually, according to this article, dimming INCREASES efficacy....

LED dimming can reduce your energy costs | Philips lighting

[Bluey]

Interesting. Manufacturers of LEDs like to quote nominal or optimal efficacy numbers. The question is where is the
optimal efficacy relative to the maximum lux of the fitting?

We never see those numbers in tests done on grow lights but we can find them on the LEDs. It's typically not linear either so makes it hard to guess too.