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Ambient Lighting Impact

Discussion in 'Lighting' started by JJP2, Jan 30, 2009.

  1. JJP2

    JJP2 Lifetime Charter Member
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    I know some of us have par meters and have been measuring. ( I didn't get one, maybe next time.) I am wondering if anyone has conducted tests attempting to determine the PAR added by ambient light.

    for example,
    measuring par with the lights out during midday and then measuring at night.
    measuring Par with the lights on during midday and then turning the lights off and remeasuring and noting the difference.

    There are likely other tests, but those are quick to mind.

    I am curious as my tank is in a very bright room so I am wondering how much/little that affects the actual light into my tank and reaching my plants.


    Anyone with any data?

    Curious,

    John
     
  2. Gerryd

    Gerryd Plant Guru Team
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    John,

    I know the Apogee PAR meters are calibrated for either ELECTRICAL light or NATURAL light or both, but I don't think both can be USED simultaneously.

    So the electrical calibration setting may not properly measure the ambient light or the reverse.

    Perhaps the more expensive meters can do this, but I don't think the ones we normally have will work.

    http://www.apogee-inst.com/pdf_files/QM.pdf

    I personally got the one for electrical only...........
     
  3. JJP2

    JJP2 Lifetime Charter Member
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    Not being familar with the meters at all, does that mean it does not detect or measure ambient light at all?


    John
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    It measures ambient light with the switch in either position, but the PAR reading will be somewhat in error if the switch is in the wrong position. The first time I used one of these meters I tried it outdoors in the shade and in the sun. I was surprised at how high the sun reading was, compared to the shade reading. Indoors, I don't recall seein more that a single digit anytime the sensor was not in the light from the light fixture. But, I didn't do the test you suggested - I wish I had.
     
  5. ntino

    ntino Guru Class Expert

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    ambient light adds 0 PAR unless you get direct light from a window.
     
  6. JJP2

    JJP2 Lifetime Charter Member
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    I don't beleive that it adds 0 PAR. PAR corresponds to the spectrum of visible light, which is what plants use for photosynthesis. This means it must add something, even if small.


    I have my tank in the middle of an extremely bright room, 2 large sliding windows on each end. There is a very noticable difference between a cloudy day vs a sunny day. On a sunny day, you can read and I can wear my shades and still see well. On a cloudy day, you can't see much without turning a light on. Based on this, I don't beleive my plants won't notice the difference either. It must have some affect, the unknown is how much. I am curious if anyone tried to measure it to get an idea if it is significant or not.

    Thanks,

    John
     
  7. VaughnH

    VaughnH Lifetime Charter Member
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    Never underestimate the ability of our eyes to adjust for widely varying light intensity. The amount of light we can read by is many times less than the amount of light that is too bright for us to tolerate. You could almost say our eyes react to the log of light intensity, rather than directly to the intensity.

    That is why our aquariums can look brightly lit with a variety of light intensities from low light to extremely high light. I vaguely recall that my very brightly lit room, which gets light from a 12 foot long patio slliding window, had much less than a 10 reading on the PAR meter when I was experimenting with it. That is a negligible amount compared to what the light fixture provides, and that is before the light makes it through the glass sides of the tank.
     
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