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Thread: Calculating Light Amounts

  1. #17
    Hello, I must be going... Not a Number's Avatar
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    Quote Originally Posted by joe002 View Post
    Not a Number – yeah it would be easier with a light meter, but since I’ve owned a number of cameras and never got a light meter I figured I would use one of my cameras. Actually, with the camera it’s pretty easy – all you have to do is measure the light at your plants, and then go outside (on a clear/bight day) and measure again, then use the table posted by Elandolf to see where you fall.

    I do own a sound level meter, maybe I could use it?
    Using a through the lens light meter is fine as long as you are aware that digital cameras have metering patterns (a feature introduced by Minolta in the 70's). Thus the meter has hot spots that are more sensitive or weighted to give priority readings. Many cameras have different metering pattern programs you can choose from. Thus if you are not aware of the metering pattern of you camera your readings can be skewed simply by having a hot spot on a dark area where a light area is expected. One stop difference will double or half the calculated lux figure. Take a reading through your camera then turn the camera upside down and compose the shot identically - most likely you'll get a different exposure reading depending on the mode your camera is set.

    As stated before to get around this either take an incident reading (the styrofoam coffee cup or incident reading cap over the lens) pointed at the light source from position of the subject (plant) or take a reading off a standard such as a grey card or a white card. If your camera has a spot metering mode use that. The important thing is to measure off a standard point of reference that fills the entire metering area (either the spot or entire frame).

    If you're able to get a light reading using a sound meter then congratulations - you've done what Einstein and quantum physicists have not - solved the Unified Field Theory Equation.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

  2. #18
    Gigantea's Avatar
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    Yeah, light and heat is the biggest issue for me. I wouldn't be able to do the maoth too work it out, but could someone twll me what the maximum heat should be inside the terrwaium? I have the Issue of just living In a place that is hot, Inside and outside. If my terrarium is 85, that's pretty "cool". I have fans thst blow but it just circulates fresh air in and old air out, its not a cooler. Then If they run for too long, I lose all humidity. Yet all I can find is a 15 minute timer.

    Temp gets too high, I lose dew from my sundews and lose humidity. Too low and i dont get humidity. Tried wet sponges, frozen bottles... I dont understand how you balance It all, doesnt seem possible.

    This morning when I woke up, the lights were of course off, the humidity was 70%, yet my plants didn't look too good so I just put then outside.

    Think I'm gonna give up terrarium, I need an outdoor setup. But that costs a ton of money too.... Can't win. Lol.

    Anyone wanna buy a t5, 4 bulb, 4 foot light? This thing just doesn't work right for me. Too big, too hot. Maybe a t8, 2 foot, 2 bulb?

  3. #19

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    What theremometer are you using? The exo-terra thermometers read really high (90+*) if water condenses in it. I put my mouth to the thermometer and suck out all the water, then look for a reading. I have noticed that the temps in the terrarium can get up to about 90* without ill effect though. How are you humidifying the terrarim? Instead of spraying, consider running an ultrasonic humidifier 24/7 and leave the top open with the lights hanging 4-6" above the terarium. I did that for a few months, and it worked really well except when the ceiling fan was running; then all the humidity left.

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