Super low light video cameras [how are they?]

Discussion in 'Amateur Video Production' started by Harry Putnam, May 26, 2013.

  1. Harry Putnam

    Harry Putnam Guest

    Can anyone here comment from experience about a camera advertised as
    being able to take usable video in really low light conditions?
    Something along this line:

    I want to fasten the camera into trees in a state park and try to get
    good video of wild pigs feeding and etc during very early morning hrs
    when they are most active. I don't want to track them and try to do
    this in person as these pigs can be very dangerous if they think you
    mean harm to piglets.

    It would need to work in very low light and be powered by some kind of
    12 volt converter and a car battery.

    Hopefully someone here has some experience with this kind of usage?
    Harry Putnam, May 26, 2013
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  2. Harry Putnam

    Paul Guest

    The product lists some kind of Sony HAD sensor.
    That's a good starting point. It makes it more likely
    to actually support low light operation. (Not like the
    one I bought.)

    A problem with operation in low light, is the noise level in
    the background. I bought a device similar to what you're buying,
    bought it from SuperCircuits in fact, but the sensitivity rating
    would put it at a level, where the noise was too high to do
    anything of value with the video. My new purchase could
    "see by moonlight", but I couldn't make out much in the
    picture. It was a blur. If I saw Sasquatch or I saw the
    mailman, the blur would have looked the same.

    You can solve this problem, with an IR illuminator.
    Note that IR is not good with a color camera, but it's
    better than relying on ambient light. (Daytime color cameras,
    actually have an IR filter to remove IR, to enhance color
    balance. Security cameras have day/night operation, where the
    filter is moved out of the way for nighttime operation. The
    description for the product, makes no mention of the IR
    filter issue at all, one way or another.)

    At first, I had to check your proposed camera, didn't have
    IR LEDs embedded in the barrel. As that is one method of
    building "zero lux" cameras. Cheesy zero lux cameras, ring
    the barrel with IR LEDs. And that's not enough light for
    long distances.

    The benefit of LEDs for this task, is less need for a filter
    to go over the outside of the light source. And with the small 5mm
    LEDs, you can get a molded lens on the end of them. I have a bicycle
    light, built with 15 degree 5mm LEDs, and I use an array of those
    LEDs (12x4 rectangular array). And the image projected by the
    light source, is rectangular as well. And the output is reasonably
    well defined, and doesn't go all over the place, like it would
    with LEDs with no lens on the end. Most of the light is clustered
    by the 15 degree beam spread of each LED.

    So what you'll need for the LEDs, is a stout power source. Like
    a car battery. If you use a car battery, you'll need a circuit
    that "cuts off" the load, before the car battery is drained
    to a dangerously low level. If you buy a 50Ah car battery, you
    can only use 10-12Ah energy, before it becomes hard on the
    battery. Car batteries are not designed for deep discharge,
    which is why you "sip" the power from the battery, and don't
    "guzzle it all down". If you buy a marine battery, or a golf
    cart battery, some of those are rated for deeper discharge.
    Limiting the amp-hours used, allows you to get more total
    overall charge-discharge cycles from the battery (like, maybe
    500). If you run it completely flat a half dozen times, maybe
    it won't take a charge any more.

    There are other battery types of course. Lithium products
    for example. They have cutoff requirements, too. You can't
    run Lithium into the dirt, because the charger is smart enough
    not to charge a "flat" Lithium pack.

    So when buying an illuminator, whether it's based on a
    "light bulb" or "LED array", you will need to protect the
    battery, for unattended operation. Check that if the illuminator
    runs off 12.6 to 13.2V or so, that it will turn off when the
    car battery is drained too low.

    My bicycle light doesn't have that problem, because it is
    powered by a bottle dynamo :) An infinite source of power,
    that all it needs is leg power to make it go. If I were to
    switch to batteries, I would need to implement a cutoff.

    My LEDs are rated 3.0V each. Putting four in series, gives
    a 12V light source. But, the LEDs conduct down to at least
    2.0V. Which means, I may set them up to draw from 12V,
    but the LEDs only dim a bit, as the battery drops to 8V.
    So if I were putting together my own LED illuminator,
    just using LEDs alone, it will damaged the battery. I would
    need to add a precise cutoff circuit, to make that stop.


    In this article, they bring up another point, which is,
    car battery voltage is temperature sensitive. When you
    have a cutoff in series with the battery, it has to be
    temperature compensated as well. That means, when it is
    cold outside, it cuts off current flow at a different
    voltage point, than if it is warm outside. Winter to
    summer temperature swing, is equal in voltage change magnitude,
    to about half the fill of the battery. Just to give you
    some idea how much of a mistake a simple "fixed and absolute
    voltage" cutoff could make, between summer and winter operation.
    So the circuit should have a thermistor or the like, to
    move the trip point a bit for summer versus winter operation.
    Or, if the circuit is not very clever, you would
    adjust the trip point, using a table of car battery
    voltage versus temp.

    If you do the math, know you'll be back to the site
    each day, in time to switch off, or recharge, then,
    no problemo.

    Paul, May 26, 2013
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