Bulb temperature and lighting....

Discussion in 'Amateur Video Production' started by Existential Angst, Feb 15, 2013.

  1. Existential Angst

    Paul Guest

    Wikipedia has some nice leads on lighting devices.

    For example, these are fluorescent lamps, 4 foot long, with a
    spectrum similar to the sun. CRI is 98. These cost about $9 each,
    and don't appear to be for sale singly. (Maybe a local lighting
    store stocks them, but otherwise you might have to buy a box of
    them over the Internet.) Color temperature is up in
    the 5000K range, like the sun. You would need a fixture with
    ballast etc, which drives up the project cost.



    The spectrum looks similar to the three-phosphor CCFLs.
    The CCFLs have a spiky spectrum as well.


    The Wikipedia article on CRI, shows these values for CCFLs.
    Some are a bit better than others. Maybe the fourth one here
    would be a candidate.

    Correlated color temp CRI

    Halophosphate warm-white fluorescent 2940K 51
    Halophosphate cool-white fluorescent 4230K 64
    Tri-phosphor warm-white fluorescent 2940K 73
    Halophosphate cool-daylight fluorescent 6430K 76

    The Philips 4 foot long fluorescent seems to have better numbers.

    A CCFL spectra is shown here. The powder blue curve is a CCFL, and
    this one has three dominant spikes in it.


    This lamp, from the Wikipedia CRI article (and associated table)...

    Correlated color temp CRI

    Ceramic metal halide 5400 96

    also sounds like a fine prospect, until you read some of the safety concerns.
    It roughly matches the Philips product, but the spectrum looks entirely
    different. Not as practical as well, in terms of being closer to a point
    source, and irritating for people's eyes.


    Exciting stuff :)

    My experience with this stuff is...

    1) The rating systems suck. You don't know what they look like,
    until you actually see one in person. Consequently, only buy
    one bulb or lighting system at a time, and evaluate it.
    2) Manufacturers will lie to sell product. (I remember one product, where
    the back of the package said "crisp white" light, which turned out to
    be brownish and dull.)
    3) DIY projects always go over budget, no matter what your
    best intentions. My project with a $20 target for price, ended
    up costing me $200. I shudder to think how much cheaper the
    outcome would have been, if I just took an off the shelf
    solution. (Probably $100 or less.)

    Paul, Feb 19, 2013
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  2. iirc, earlier in one of these lighting threads I mused about mounting a 4 ft
    fluorescent fixture on its end, and standing it on the floor, for a similar
    effect, and apropos of Paul's post. The curved reflector would lend itself
    to hitching filters, diffusers etc as well.

    I've got enough portable fixtures and wall-mounted stuff that hopefully with
    the "right" cfl's should be OK.... if not, I'll explore all the ideas in
    these threads.
    Existential Angst, Feb 19, 2013
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  3. I hear dat! And that's not even counting your TIME!!
    With diy, you gotta know how to pick yer battles.... :) :)
    Nice links, innersting stuff.

    I'm hoping warm-cards etc make a lot of this moot.
    Hopefully I'll achieve a proper mix of uniform/accented lighting, and the
    white balancing will take care of the rest. Steve's link on the warm cards
    was really striking in the effect of this white balancing on skin tone.

    I could always go for a film noir/Humphrey Bogart effect in my fitness
    demo's.... lol
    Existential Angst, Feb 19, 2013
  4. Existential Angst

    j Guest

    That is really sweet. My Dad's house, that he built, has a cove ceiling
    living room with fluorescent lights, end to end, hidden in window
    valences. Nice indirect ceiling light, very bright, but also harsh with
    those ancient bulbs.

    That would be a nice project, but as you say with DIY projects, full of
    cost overruns (ballasts,brittle wiring...)
    It seems that Philips know how to make good phosphors.
    It's interesting that many grow lights have high CRI's. This ceramic
    metal halide is a drop in replacement for a HPS which has a lousy CRI.

    I have one,the light is not unpleasing.
    Indeed. And quality of light is getting to be as important as amount of
    light. The technology is almost there. 98 CRI in a t8 or a t12 is
    striking. It appears the more energy dense phosphors in CFLs are harder
    to adjust. But it will happen. I'm waiting on improvements to the cold
    cathode CFLs as they are dimmable...
    Thanks for taking the time to post this.

    j, Feb 19, 2013
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