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The visible part of light

Discussion in 'Home Power and Microgeneration' started by Jimes, Jul 3, 2006.

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  1. Jimes

    Jimes Guest

    I see lots of talk about the low power consumption of the low power lights,
    but I'm missing something...

    Normally, people speak about a preference for a 100W light or a 60W light,
    beacuse they are concerned with the amount of light produced. Now the Watt
    rating actually refers to it's consumption, and not the amount of light

    I personally think the low voltage 50W bulbs give the best light, and these
    9W minature flourescents the worst, but I'm speaking about the quality of
    the light produced. The low voltage lights produce a full bodied pyramid of
    light, whilst these 9W low power ones produce a sickly sort half hearted
    light (just an opinion). Fact is though, the 9W lamp is far more attractive
    for the minimal power it consumes.

    My question is, what are the terms of reference to describe the amount of
    light given off, (not the power consumed)?

  2. Jimes

    Jimes Guest

    Partial answer to my own question....

    I'm looking at lumens per watt....but if the manufacturer of the light bulb
    like Phillips doesn't put it on the box... can it be calculated?

  3. No, you want total lumens, which tells you how bright a light is. CR
    (Color Rendition) is a number used with flourescents to tell you how
    'good' a light is (you can somewhat determine this number from the
    color temperature of the bulb).

    L/W is a measure of efficiency.
  4. Guest

    I'm looking at lumens per watt....but if the manufacturer of the light bulb
    No, but you can easily compare a known with an unknown light source with
    a grease-spot photometer. Put a grese or oil spot on a 3x5 card and walk
    between the sources until the spot disappears, which indicates that it is
    equally illuminated on both sides. The relative source luminosities are
    then proportional to the inverse distances squared.

  5. Eeyore

    Eeyore Guest

    All the Philips CFs I've seen have a lumens figure. Maybe for the European
    market perhaps ?

  6. Vaughn Simon

    Vaughn Simon Guest

    I have been using 12v Edison base CFs for yard lighting for years. I find:
    iv) To be honest, you could also mention that 12vdc on an Edison base
    socket is a very non-standard configuration and subject to
    embarrassing/moderately expensive accidents.

    v) I keep a couple around for emergency lighting. They allow us to have
    very normal room lighting with very reasonable battery drain without running a
    generator. Someday, I will wire some in permanently and use them off of my 12v
    PV system for normal everyday lighting.

  7. George Ghio

    George Ghio Guest

    Part of what you are missing is light placement. My house has 56
    separate lamps. 26 of which are LED lamps.

    The highest wattage lamp is 1 - 20 Watt lamp.

    All the other incandescent lamps are either ten Watt or five Watt lamps.

    The led lamps are used for either reading lamps of back ground lighting.

    All lamps are 12 volt.

    Placement is everything. The old standard of a 60 or 100 watt lamp in
    the middle of the ceiling is dead as far as my usage is concerned.
  8. Mary Fisher

    Mary Fisher Guest

    A central light has its uses according to what you're doing in the room -
    but even 100W isn't sufficient for me :-(

    Placement IS everything. I wonder why we don't have general lighting to
    shine from window areas when natural daylight goes?

    just musing
  9. George Ghio

    George Ghio Guest

    Not often. Most work stations are around the sides of a room so with a
    central lamp in the ceiling you cast a shadow wherever you work. Could
    explain why 100W is not enough.

    Example: The pasta bench. Eight feet long, three QH lamps 600mm above
    the surface, lamp in the middle = 10W with small metal reflector, lamps
    500mm either side = 5W with small metal reflectors.

    Metal reflectors are the tops of spray paint cans with the centre
    drilled out, painted flat white and fitted with ceramic QH lamp holder.
  10. Mary Fisher

    Mary Fisher Guest

    Um - I did say, "according to what you're doing in the room". :)

    In our sitting room and dining room we don't have workstations, we have a
    table lamp on, er, the table for winter suppers for two. When we have
    company to dine we use an overhead central light. If I'm (hand) sewing in
    the sitting room I have a lamp. When we have company we use the central
    overhead light.

    There are no workstations in the bedrooms or bathroom come to think of it.

    My office has an overhead light between me and the pc. My workroom has three
    spots lighting different parts of my workbench. There's an additional light
    over the filing cabinets. Spouse has a lamp on his desk.

    Overhead lights in the hall and on the landing work well, but we do have
    three spots lighting pictures on the landing.
    I repeat: I wonder why we don't have general lighting to
    shine from window areas when natural daylight goes?Mary
    still musing
  11. Mary Fisher

    Mary Fisher Guest

    What does 'good' mean?

    I thoroughly dislike what I call the 'quality' of light from long life
    bulbs, is this the same thing? They seem to give everything a dull,
    yellowish tint. It's very difficult to explain :-(

  12. A home designer I know did exactly that - general lighting shines _through_
    the windows from outside. Besides providing light in approximately the
    same places as you get in daylight, it has the added facility of providing
    privacy - outside viewers see reflected light not the people inside. Seems
    like a waste of energy, to me, though.
  13. Mary Fisher

    Mary Fisher Guest

    Well, not a huge amount would be lost through the glass, have I missed
    another factor?

    Did the designer use his system or replace it with somethinig else?

  14. Color Rendition index is a method of telling how well a light will
    produce the full spectrum. Sunlight is considered the best and
    everything else is compared against that standard. A low number
    will mean that colors will look different than under sunlight.
    Yellowish tint is a very good way to explain it. Such a light has
    a low color temperature. Color temperature is based on the concept
    that with an incandescent light the hotter it is, the more blue the
    light it produces. Low temperature incandescent bulbs produce a
    very red or orange light. Fluorescents don't work the same way but
    it's possible to describe their overall light spectrum by temperature
    as if they did.

    Personally, the higher the color temperature, the better.

  15. A significant amount gets reflected off the glass.
    It's in use now.
  16. Jim Baber

    Jim Baber Guest

    Jim Baber wrote:
    There are two things related to the quality of light given off by any

    * The Lumen which deals with the intensity / quantity of light, and
    is usually stated as either Lumens (the total of all light being
    generated at this voltage and current) or as Lumens per Watt.
    * The color temperature, usually stated as degrees Kelvin. This is
    literally the color of the light emitted by the light in the terms
    of how hot any object has to be to give off light of this color.
    Jim Baber
    1350 W Mesa Ave.
    Fresno CA, 93711
    (559) 435-9068
    (559) 905-2204 (Verizon IN cellphone (to other Verizon IN accounts))
    See 10kW grid tied solar system at ""
    See solar system production data at ""
  17. Mary Fisher

    Mary Fisher Guest

    OK, thanks, I'd like to think I'll remember that.

    Now, how does one know the colour temperature before one pays for a product?
    'Daylight' seems to be the only variant we can get here (UK) and they're
    VERY expensive. People seem to be satisfied with what's on offer. Perhaps
    they're watching telly all the time so it doesn't matter, it matters to us.

  18. Mary Fisher

    Mary Fisher Guest

    Hmm. Well, knowing a bit about designers I'd be happy with such a commitment

  19. George Ghio

    George Ghio Guest

    Table - workstation
    Chair for sewing - workstation
    You never read in bed and there is no mirror or counter top in the bath.
    Because it is inefficient, wasting energy.
    Well, it seems that you have, in fact, adjusted your life around the
    lighting supplied. Common practice in existing homes.

    I adjusted the lighting around my needs as I built. Far more satisfying
    in the long run.
  20. Mary Fisher

    Mary Fisher Guest

    You call eating work???
    Sewing isn't work either, for me. I do it for pleasure.
    We do
    There are both in the bathROOM. And we read in the bath.
    LOL! Don't think that we haven't considered lighting, we have. That's why we
    decided to keep the central overhead lighting as well as having spot
    lighting where it's needed. But our house isn't a series of workstations!
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