Inaccurate LUX/PPFD readings

[guccisimo85]

I will preface this by saying that measurements have only been taken on two iphone apps ... I do not yet have a light meter and I think the ones that measure PAR/PPFD are quite expensive...

My problem is that I have measured lux and PPFD in various locations. I seem to be getting correct PPFD numbers (50-70 by a bright window), but my lux measurements seem low for that PPFD (2500 lux max). I am even more confused because when I tried taking measurement in direct sunlight, I seem to only get max 250 PPFD and 10,000 lux.

Anyone have an idea what the problem may be?

Thanks!

EDIT: I have ordered a proper light meter (measures lux) which is supposed to arrive tomorrow!