How to optimize life of photoflood bulbs

Discussion in 'Professional Video Production' started by aristotle, Nov 25, 2004.

  1. aristotle

    aristotle Guest

    I need to take 2500-3000 digital photographs of antiques using 250
    watt blue BCA photoflood lights. Is there anyway to extend the life
    of these bulbs beyond the 3 hour life expectancy. Will it help to use
    a dimmer to reduce power between changing art objects or turn off the
    bulbs between object changes.
     
    aristotle, Nov 25, 2004
    #1
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  2. aristotle

    Crownfield Guest

    your camera can do a white balance perfectly.
    blue daylight photofloods will be
    about the most expensive way to do that.
    have you looked at the rated life of them?

    turning them on will shorten the life even more.
     
    Crownfield, Nov 25, 2004
    #2
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  3. aristotle

    MSu1049321 Guest

    Do not bump or move them while they are hot or immediately after turning them
    on or off. If you use a simple resistive dimmer, you're going to change the
    color balance you seem so anxious to maintain. Frankly, I think the pulsing of
    anm ultra-fast-rate digital dimmer is going to damage the filament more than a
    steady, even strain.
     
    MSu1049321, Nov 25, 2004
    #3
  4. aristotle

    Bob Williams Guest

    Using a dimmer instead of turning the lights on and off may give you a
    slight (10-15%) increase in lifetime but hardly worth the trouble.
    As Crownfield indicated, your camera's White Balance may work with
    regular incandescent lights just fine.
    However, I use special 26 Watt" Full Spectrum" compact fluorescent
    lights that have a color temperature of 5500K and a CRI of 93. They cost
    about $15 but they have a lifetime of 15,000 hours. Also they run very Cool.
    The color is very close to daylight and doesn't even require a special
    WB setting. Check Google (Full Spectrum Fluorescent Bulbs) for vendors.
    Bob Williams
     
    Bob Williams, Nov 25, 2004
    #4
  5. "aristotle" wrote
    If you do not need to use blue photoflood bulbs (you probably need to, don't
    you?) then there is another option.

    If you have to use medium base screw in photofloods, why not use the ECA 250
    watt white 3200k photoflood bulbs instead? They only cost about fifty cents
    more per bulb, and they are rated at 20 useful hours for the correct color
    temperature. That means your bulbs will last almost seven times longer for a
    minimal increase in cost. (They are under three bucks a bulb)

    Now, if you just gotta use a blue photoflood you can dim it no more than 10
    percent (of it's rated voltage) and still have an acceptable color
    temperature to work with. (if you can white balance that camera) You will
    also double the life of the bulb to possibly six hours.

    As a side bar, I'm gonna move away from tungsten and on to Halogen. When you
    dim Halogen bulbs for extended periods, it inhibits the halide cycle
    (re-depositing evaporated tungsten back onto the filament) which reduces
    effective bulb life. To get around that, just be sure to run your halogen
    lights back up at full power for a few minutes.

    (ps. Please ease up on the cross-posting)

    Regards,
    Bill F
    www.billfarnsworthvideo.com
     
    Bill Farnsworth, Nov 25, 2004
    #5
  6. Standard 500W or quartz 500W lamps should work fine. You should not
    need daylight lamps, unless you are trying to match some existing daylight.
    If so, consider filtering the daylight with plastic film made for the use.
     
    Joseph Meehan, Nov 25, 2004
    #6
  7. aristotle

    Beemer Guest

    Aristotle,

    I also have the same bulbs you are intending to use. Do not use a
    variable frequency dimmer as you will shorten the life significantly
    through filament vibration especially at low output. As all photofloods
    are voltage overrun you could use a tapped auto-transformer (multiple
    voltage selection but no input/output isolation so NEVER use with low
    voltage applications) to drop the voltage say 10-15% which will return
    the bulb to a standard bulb lifetime but of course corresponding
    dropping of colour temperature.

    However if you sum the cost of the bulb plus the kw/hours you will have
    this lamp (lamps?) running you could pay for an external camera flash
    and a slave flash which will give you 5000K colour temperature

    regards,

    Beemer
     
    Beemer, Nov 25, 2004
    #7
  8. I might add that dimming will change the colour output.
     
    Joseph Meehan, Nov 25, 2004
    #8
  9. aristotle

    JPS Guest

    In message <>,
    Possibly better, because most digital cameras are least sensitive in the
    red channel, and the warm light increases the signal-to-noise ratio in
    the red channel (which is usually higher than the other channels in
    daylight exposure).
    --
     
    JPS, Nov 25, 2004
    #9
  10. aristotle

    JPS Guest

    In message <4ulpd.37575$>,
    All the better. Most digital camera's CFAs favor warm light.
    --
     
    JPS, Nov 25, 2004
    #10
  11. But it could be a problem if the OP wanted to match some sunlight coming
    in a window in the background.
     
    Joseph Meehan, Nov 25, 2004
    #11
  12. aristotle

    secheese Guest

    I assume by "optimize" you mean maximize. The answer is yes.

    You probably have noticed that most incandescent bulbs fail during
    power up. This is because the filament flexes violently, and breaks,
    during the rapid transition from cold to hot.

    If you make use of a dimmer you will extend the life of the bulb
    dramatically because the filament temperature will rise slowly
    (relatively speaking). But, spend a few bucks and get a solid state
    dimmer (not the rheostat types). Solid state dimmers use a
    zero-crossing thyristor to control the power applied to the bulb.
    This will reduce thermally-induced filament stress and extend bulb
    life.

    As an example, a number of years back, we had a ornamental lighthouse
    on our lawn. The 60W bulb in it would flash every four seconds. We
    would get a couple of months max before the bulb blew. I replaced the
    mechanical flasher, with a thyristor-based flasher that I built. The
    bulb was still flashing after 4 years of 24/7 operation. Might have
    still been going if the lighthouse hadn't been vandalised.

    Regards.
     
    secheese, Nov 26, 2004
    #12
  13. aristotle

    secheese Guest

    I disagree completely; see my response to the original poster. Using
    a dimmer (solid state type) to slowly bring the bulb to full power is
    a great way to extend the filament life.
     
    secheese, Nov 26, 2004
    #13
  14. aristotle

    Jer Guest

    secheese wrote:

    And all this time I thought incandescent bulbs died because a leak
    during the previous cool down caused the vacuum inside to fill with air.


    [....]
     
    Jer, Nov 26, 2004
    #14
  15. aristotle

    none Guest

    If you want daylight flourescent just go buy plant grow tubes, they'll
    have a daylight balance and cost much less.(though on all of my
    cameras the balance has a flourescent setting to allow shooting under
    regular tubes as well.)
    Gotta ask why you don't use a strobe instead?
     
    none, Nov 26, 2004
    #15
  16. aristotle

    Beemer Guest

    You are correct and I retract my statement. The low frequency thought I
    had came from the distant past where, instead of photographers using
    series/parallel switches to control light output, some folks used
    diodes. When a diode is used it results in 25Hz operation and this
    resulted in the premature failure.

    Thanks

    Beemer
     
    Beemer, Nov 26, 2004
    #16
  17. aristotle

    Michael Guest

    Dear Aristotle,

    Your question on lamp life and all the very informative replies reminded me
    of the "Tungsten Water Cycle" and it's effects on the longevity of filament
    life. How could everyone of forgotten this

    Basically the intense heat of the filament brakes down water molecules that
    were left inside the glass envelope during manufacture of the bulb into
    hydrogen and oxygen atoms. The oxygen then reacts with the filament and
    makes tungsten oxide which evaporates and condenses on the bulb wall. Then
    the hydrogen which was freed reacts with the cold tungsten oxide on the
    bulb wall, which takes the oxygen away from it, and reforming the water
    molecule. Which leaves a coating of dark tungsten metal on the glass. The
    water molecule which was reformed drifts back to the filament, and the
    whole cycle is repeated again.

    Now in halogen lamps the "Tungsten Halogen Water Cycle" comes into play.
    In these lamps the tungsten combines with the halogen gas in the lamp
    envelope and is re-deposited back onto the filament. This is why halogen
    lamps last longer.

    And something which always surprised me is that lamps will last longer when
    run on an AC voltage than a DC voltage.

    <http://www.harison-toshiba.com/lampinfo.htm>

    Michael.......
     
    Michael, Nov 28, 2004
    #17
  18. aristotle

    Michael Guest

    And bulbs turn black on the inside because the filters on the power line
    outside your house need changing. Allowing dirty electricity to pass
    through.

    Sort of like when the filter on your fish tank needs changing.

    Michael......
     
    Michael, Nov 28, 2004
    #18
  19. aristotle

    david.mccall Guest

    Traditional wisdom would say that running a light on a dimmer will
    make it last longer, and this may be true for normal household lamps,
    but halogen lamps may be a different story.

    The "water cycle" discussed above doesn't work as well if the lamp
    isn't up to its full operating temperature (the term "water cycle" doesn't
    ring a bell, but the principal is basically correct, and the term may be
    as well. I just haven't heard it). If the gasses in the lamp aren't hot
    enough
    to cause the molecules to re-join the filament, it can develop week
    points and can often fail prematurely.

    All lamps are susceptible to early failure if they get jarred while the
    filament
    is still hot, so it is always best to let them cool down before moving them.

    Photoflood lamps are brighter than household lamps by essentially running
    them hotter. The hotter the filament, the brighter the light and the higher
    the
    color temperature, but the shorter the life.

    Bill is probably old enough to remember the old Colortran system. It was
    a power transformer with several output voltages ranging from below
    the normal voltage to quite a bit over voltage. The idea was to use common
    R-40 lamps (~2600 Kelvin) for film production. You could drop the voltage
    to "save the lamps" while setting up, the goose them to a higher voltage
    while shooting. By raising the voltage/color temperature, these lights could
    be mixed with the studio lamps that also had a short life span in those
    days,
    and they were very expensive. Colortran sold a small "bay light" that could
    take 5 R-40 flood lamps (as well as singles) to be used with this system.

    The original Lowel lights also used R-40s, but were intended for R-40
    Photofloods, but they could also be used with common R-40s and then
    plugged into a Colortran transformer. See, now you know where Colortran
    got it's name.

    The original Lowel lights were pretty neat (they may still sell them). The
    idea
    was to make a light kit that could travel easily. 6 fixtures, with barndoor
    sets,
    could fit in a small briefcase. Lamps could be brought along, or you could
    just pick them up at a photo or hardware store (photo stores would have real
    photoflood lamps).

    The fixture was a small aluminum plate with a swiveling socket attached.
    It could be taped to anything, or slipped behind moldings. It could be
    nailed
    or screwed, and it had a ball-chain and slot so it could be tied to a stand,
    pipe, or anything up to a 2 X 4. The barndoors were fit to the lamp itself,
    and
    folded flat for storage. A very cool/versatile system.

    David
     
    david.mccall, Nov 28, 2004
    #19
  20. aristotle

    MSu1049321 Guest

    They still make the original Lowel system you describe, and my opinion is that
    it is a great value for beginning Dv "film makers" on a budget.
     
    MSu1049321, Nov 28, 2004
    #20
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