Side-by-side PPFD meter results for:
- Apogee SQ-520
- Photone
- Home Studio PPFD meter
Results are as follows:
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Awesome post. 
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Thanks for posting. I use a PAR meter with quantum sensor but have never compared to the phone app and whatnot.
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So 516 avg.
Which do you believe to be true? 
I trust the Apogee results more. The Apogee sensor is calibrated to read the full photosynthetic spectrum of a light. A phone camera is only calibrated to capture the visible (to humans) spectrum of light.
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How close is the Apogee reading to HLG spec sheet of your light?
I didn’t look at the spec sheet. There are too many variables in the test environments to make a legit comparison.
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Understood 
I looked at the site and couldn’t find the spec sheet. Was mainly just curious.
Thanks for the post, pretty cool 
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Sorry @MidwestGuy stopped long enough to adjust my train of thought and realized I was just cluttering your thread.
Appreciate your efforts and great information for folks who want to know. 
No worries, mate. All comments are welcomed.
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Tunnel vision is good sometimes, not ALL the time… I get curious out loud. 
Do you plan to pick up a Uni-T? Or have one available?
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I only have the Apogee meter.
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Sorry to be late to this thread.
@MidwestGuy : Did you test the Photone app on an iPhone or an Android? If the latter, it would be worth comparing again, using the updated version of the app.
Photone didn’t have correction factors for Android cameras when you did the comparisons, so they used the ambient light sensor, which was less accurate. The new version should give equally accurate results on either type of phone.
Phone cameras aren’t calibrated at all, as far as I know. But the sensors respond to wavelengths well outside the visible spectrum. That’s why, for example, you can see whether an IR remote is sending by looking at its LED with your phone camera while pushing a button on the remote.
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