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Wondering if anyone has any insight on some par readings I took using my Apogee SQ420 par meter on two different lights I have around.

Since the lights are different lengths, I took the measurements both in the open air and inside an opaque, non-reflective 12" x 12" x 12" open topped box. The in-the-box measurements were meant to equalize for the different lengths of the lights (i.e. only a 12" section of light was over the box, the edge of the lights hanging over and not contributing to PAR).

Readings for both lights in open air are lower than the advertised PAR at those distances. I assume that has to to with calibration errors of the SQ420 (it is calibrated for T5 fixture, looks like the error rate for LED from the specs is 5-10%). However, what surprised me is that the Ray 2 seems to have the same or slightly higher PAR when measuring in-the-box. To me, this means the Ray 2 has the same light intensity per inch of light as the Satellite Plus Pro. Based on the advertised PAR at 12" for each light ("100+" for the Plus Pro and 74 for the Ray 2), I would have expected my Plus Pro readings to be ~25% higher in the box than the Ray 2. In general, my Plus Pro readings are a fair bit lower than expected.

Any thoughts?


Finnex Ray 2 24"
Par @ 12" (open air) = 63
Par @ 12" (inside box) = 48


Current Satellite Plus Pro 36" (all LEDs set to max)
Par @ 12" (open air) = 72
Par @ 12" (inside box) = 47
 
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