Lux - par conversion

[ajadcock]

Hi all,

In trying to find some PAR figures for my led fixture I happened across this info:

"Converting Lux to PAR

If you have a lux meter, it is possible to convert lux to PAR. Since spectral quality plays a part in these conversions, each light source (actinic lamp, 6,500K metal halide, etc.) will have a difference factor. The equation is:

Lux ÷ Constant = µmol·m2·sec

Lux to PAR Conversion Factors Light Source

Sunlight - 54
Warm White Fluorescent - 76
Cool White Fluorescent - 74
URI (now UV) Actinic Fluorescent - 18
URI (now UV) Daylight Fluorescent -54
Actinic/Daylight Combination - 38
Philips 03 Actinic Fluorescent - 40
Panasonic 6,700°K Power Compact - 72
Panasonic 7,100°K / 6,700°K Combination - 55
Osram Powerstar Metal Halide - 57
Ushio 10,000°K Metal Halide - 54
Coralife 10,000°K Metal Halide - 30
Venture "Daylight" Metal Halide - 46
Radium "Blue" Metal Halide - 51
Fusion Sulfur Lamp - 41
Westron Mercury Vapor Lamp - 70
Iwasaki 6,500°K Metal Halide - 57 "

Sorry that's not terribly clear but I'm posting from my phone!

So is there anybody who has a PAR meter and LUX meter and can test this out?
All I'm thinking is maybe people can get ballpark figure of the par values of their light fixtures.
Even to the point where the LUX meter many phones have built in could be used?

Feel free to shot me down in flames, this is definitely not my area of expertise 🙂

Adam

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[ajadcock]

So just out of interest I fired up a lux app on my phone, pointed it at the sun and got 66000 lux.

This is roughly half the expected value for 12noon so seems vaguely accurate as its evening now?

Moving on from this I measure the lux output of my led at substrate level (285 lux) and used the conversion for cool white florescent (I know I know -I have LEDs ) which equates to less that 4 par. Using the sunlight conversion that's just over 5. Interesting don't know what to make of that.

Keen to see other peoples thoughts!

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[Parablennius]

Mornin'
I too am playing with a home-made LED system on my new tank. I bought a lux meter and with my LED's @ 60% ( a mix of 4000K and 6500K ) and I got a reading of 3000 lux @16" distance. From another plant forum I read to divide lux by around 70 to get a PAR value. So around 4. I think this is too high for a near low tech system on a 6 hour photoperiod. Also keen on other opinions.
Cheers