Below are the spectral distribution charts of two EYE HORTILUX grow lamps with very different spectrums – the Daylight BLUE Metal Halide and the Standard Metal Halide. When the charts are compared side–by–side, the difference in the quality of the two spectrums becomes readily apparent. The BLUE delivers a broad, full spectrum for your plants whereas the Standard Metal Halide provides a spectrum full of peaks and valleys and areas of lower spectral output.
When comparing those two spectrums many would guess the BLUE has more PPF than the Standard Metal Halide. However, the opposite is actually true – the Standard MH has 40% more PPF than the BLUE, yet the BLUE is clearly the better grow lamp due to the quality of the spectrum and how closely it mimics natural sunlight. In essence, PPF (and PBF) is a measurement of intensity and is in no way related to the quality of the light’s spectrum.