Question: Shooting under sodium vapor lights

Discussion in 'Professional Video Production' started by PTravel, Jul 2, 2006.

  1. PTravel

    David McCall Guest

    Have you seen a spectrum anaylisis that shows this "falloff"?

    It's been a long time since I've seen one, but I seem to remember
    a chart with a a tiny bit of noise at the baseline, and the spikes
    were just thin vertical lines. They once used sodium vapor lights
    to light the background for process shots. It seems strange because
    the orange spike of the lights is so close to the colors in flesh tones,
    but they were still able to pull a matte. It is quite "pure".

    Flourescent lights also have these extremely narrow spikes, but the
    phosphers added to the inside of the tube produce a glow with a
    wide enough spectrum to allow you to see colors. Depending on
    the phosphers used, the color rendering quality will be of better
    on some lamps than others (usually tracks with the price of the bulb :).

    David
     
    David McCall, Jul 3, 2006
    #21
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  2. Yeah. That's pretty much the answer, Richard. It is what it is. And in
    my opinion, The color of Paul's footage is quite pleasing.
    Again, it is what it is and at night, that is what we see anyway.
    If you ain't got the budget to change all the globes in the shot to
    tungsten or metal halide then there isn't anything that can be done to
    correct the shading where one would ideally like it.
    In some areas streetlights on minor roads, parking lots and pedestrian
    walkways are now being converted over to full spectrum 3200 LEDs.

    Bill F.
    www.billfarnsworthvideo.com
     
    Bill Farnsworth, Jul 3, 2006
    #22
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  3. PTravel

    David McCall Guest

    The best is to have a bubble on the base of the head, but placing
    the level on the camera will do the job on a shot with limited
    camera movements (pans, etc.) if the camera has a flat spot
    you can use as a reference.

    I've seen small rectangular bubble levels in photo stores
    (on a key chain IIRC). You might find something usable
    at the Home Depot, or other home improvement store.

    David
     
    David McCall, Jul 3, 2006
    #23
  4. PTravel

    Mike Fields Guest

    Well Paul, for what it's worth, both my wife and I really
    like your clip as it is. We both think that changing the
    color balance (or altering it) would spoil the effect.
    Our $0.02 ...

    mikey
     
    Mike Fields, Jul 3, 2006
    #24
  5. The astronomers must hate that. So much for the
    International Dark Sky Association
    http://www.darksky.org/
    They loved sodium vapor, et.al. because the terrestrial
    light pollution could be so easily filtered out.
     
    Richard Crowley, Jul 3, 2006
    #25
  6. PTravel

    PTravel Guest

    What I propose is no different than expanding dynamic range in an audio
    compander. A 1/10th nm difference would be expanded into a 1 nm difference,
    etc. It would not result in posterization, as the number of discrete levels
    is not being reduced.
    I used my video as an example only of the monochromatic effect that results
    from shooting under Na lights.
    I never said it was simple. I do think, though, that you don't know what I
    have in mind.
     
    PTravel, Jul 3, 2006
    #26
  7. PTravel

    PTravel Guest

    I'm not sure it's impossible. Notching 589 nm is certainly possible -- it's
    the remaining 5% that I'm interested in playing with.
    Not an option, unfortunately.
     
    PTravel, Jul 3, 2006
    #27
  8. PTravel

    PTravel Guest

    No, I haven't. I'd suspect the fall-off is fairly steep since the light is
    produced by atomic excitation which, I'd think, would make it easier to
    isolate spectra from the impurities.
    Hmmm. The question, though, is how much "impure" light would be needed to
    create false-color effect?
    My idea may not work at all. One thing I've noticed in my travels, though,
    is that different cities that I've shot apparently use different "flavors"
    of Na lamps, and some have somewhat broader spectra than others. For
    example, the lamps in Copenhagen shoot white, as opposed to the distinctly
    orange lights in the Amsterdam video. Though the Copenhagen light still
    puts out limited spectra, and everything has a distinctive red/amber tint,
    other colors, e.g. green, are discernible.
     
    PTravel, Jul 3, 2006
    #28
  9. PTravel

    PTravel Guest

    This is going to be hard. I shoot with a VX2000, which doesn't really have
    any flat spots on top, except for the VCR controls -- sticking on top of
    them really isn't an option. The handle is a possibility, but it's slightly
    rounded. Maybe I can make something that will fit into the hot shoe
    connector.

    I use a Bogen 3160 fluid head, primarily because it's the smallest and
    lightest fluid head I can find that uses a Bogen quick connector that is
    positioned horizontally, rather than vertically (like the RC2, for example).
    I have a angle bracket that I use with my digital still camera, and it
    requires the quick connect orientation of the 3160 to allow tilting the
    camera up and down, rather than sideways.
     
    PTravel, Jul 3, 2006
    #29
  10. PTravel

    PTravel Guest

    Thanks. I'm probably an example of "Amateurs Gone Wild." My audience is
    limited to my wife, my in-laws in China, whatever friends I can coerce into
    watching my videos, and whatever poor soul happens to stumble onto my
    website. My primary goal in doing these videos is just to create a
    remembrance of our travels and, hey, that is what it looked like. ;)
     
    PTravel, Jul 3, 2006
    #30
  11. PTravel

    Larry in AZ Guest

    Waiving the right to remain silent, "PTravel"
    Eyeball the vertical objects, rather than the horizontal. Horizontal
    lines that are not perfectly tangent to your shooting direction should
    not be made to appear level. That will throw off the verticals.

    Make verticals correct, and you'll have properly composed shots.

    As for the stick-ons, I've seen them. Try a good hardware store or
    Google search.
     
    Larry in AZ, Jul 3, 2006
    #31

  12. I don't doubt it.
    Nocturnals are grumpy creatures.

    Bill F.
    www.billfarnsworthvideo.com
     
    Bill Farnsworth, Jul 3, 2006
    #32
  13. First off, as I and several others have said, Paul's video looks damn
    fine as it.

    But I had a bit more of a "think" on this one.
    What's wrong with it.
    Nothing. The street lights came out just as we see them. A bit orange.
    And if there are any Mercury Vaps then they would be green........
    just as we see them.
    However, what is not being seen as natural (natural for Sodium Vap
    light, that is) is the sky and shadows are not black. They are
    slightly orange.
    IRL we see the orange (or green) light. But.......... for all intents
    and purposes, we also see the night sky as black.

    Now, throw away the black balance issue for a bit and think about
    this....

    When you are shooting under street lights or with street lights in the
    shot, you will have a lens flare issue. Especially a dusty lens or
    filter. And that flare well lighten the image a bit off to the range
    of the color temp of the offending light(s).

    With me so far?

    So along with everything else that has been suggested make sure the
    lens and filters are dust free.
    Use a larger lens shade.
    And ......... toss a polarizer on that puppy and dial it in a wee bit
    to see what you get.

    Bill F.
    www.billfarnsworthvideo.com
     
    Bill Farnsworth, Jul 3, 2006
    #33
  14. Here's a couple of graphs:
    http://www.cis.rit.edu/~ejipci/Reports/SpectralDist_of_Sources.pdf

    They all look pretty narrowbanded. Maybe with a colourcorrection filter you
    could move some of the peaks around a bit, but then you would have to know
    which lamps they use exactly. And it will only change how the lamp looks
    like, and not change the look of the environment. Unless of course you
    would put a gel on the lamps.

    cheers

    -martin-
     
    Martin Heffels, Jul 3, 2006
    #34
  15. That is a "simple" secondary colour-correction, where you can change the
    gamma, saturation, hue etc of a colour within a certain range. But you know
    from colour-correcting, that if you try to "pull-up" a dark bit, this goes
    with the introduction of noise.
    If you look at the graphs in
    http://www.cis.rit.edu/~ejipci/Reports/SpectralDist_of_Sources.pdf you will
    see spikes at different parts in the spectrum as well, which would reflect
    on the matching colours.

    cheers

    -martin-
     
    Martin Heffels, Jul 3, 2006
    #35
  16. PTravel

    PTravel Guest

    Ooooh --- fantastic point! In this instance, the lens was clean, but I
    usually don't use a lens shade at night -- I guess I should. It also never
    occurred to me to use a polarizer at night -- another great idea!

    The lens shade would have been impossible in this instance because I was
    using the rain cape on my camera, and it won't accomodate a lens shade.
    Also, it was misty and rainy, so there was a lot of light reflection from
    the sky.
     
    PTravel, Jul 3, 2006
    #36
  17. Ever heard of lightspill against the clouds? that's what's wrong with it
    :) It's the lightpollution of a city, and I am sure a lot of MV's will
    illuminate the clouds as well. Enough to make them look funny orange as
    well. Checkout the night exteriors at "Collateral", shot by pros which have
    access to all the toys, on digital (Thomson Viper). Looks funny as well.

    cheers

    -martin-
     
    Martin Heffels, Jul 3, 2006
    #37
  18. PTravel

    Toby Guest

    A small piece of plastic or metal cut to fit the hot shoe is easy. Glue a
    small pedestal on top to clear the shoe and glue the level to that.

    I've had a similar thing mounted to my big videocam for years. It is
    completely useful when shooting shots from the ground, for instance, or even
    referencing level when the camera is on my shoulder in situations in which
    there is no handy horizontal reference.

    Toby
     
    Toby, Jul 4, 2006
    #38
  19. PTravel

    Toby Guest

    May I suggest that you think about more varied framings? I liked your clip
    but found that one medium shot after another was not very exciting. Think
    about closeups, tele shots, extreme angles, big foreground objects, etc. to
    intercut with the more useful vanilla stuff.

    Toby
     
    Toby, Jul 4, 2006
    #39
  20. PTravel

    PTravel Guest

    Thanks, Toby. It didn't even occur to me to make one -- I've spent the
    afternoon looking for something ready made. It should be easy to make the
    thing.
     
    PTravel, Jul 4, 2006
    #40
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