Flourescent Heck

Discussion in 'General Shop Talk' started by wildmaven, Sep 28, 2007.

  1. wildmaven

    wildmaven TPF Noob!

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    I am going to be doing a photo shoot this weekend inside a government building and just got an email saying that they will be unable to shut off the flourescent lights. I'll have my 2 light sets and backgrounds, but it's just me doing the shoot, so I won't be able to have anyone hold anything to block the lights, and I can't put tape, tacks, etc in the walls to hold anything. Shooting outside is not an option. Any suggestions?? I've been asking them for over a week about the lights and they finally get back to me the day before the shoot. :er:

    Marian
     
  2. Digital Matt

    Digital Matt alter ego: Analog Matt

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    If you are using strobes, shoot at your x-sync speed and you'll overpower them.
     
  3. Helen B

    Helen B TPF Noob!

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    It may be that you can use a high enough shutter speed and a small enough aperture to make the contribution of the florries negligible - ie your flash (if you use flash - you don't say) totally overpowers the ambient light. That's the usual way. One case in which it may not work is when the sync speed is too slow - like 1/30th, for example.

    What sort of lights are you using (flash, tungsten, studio fluorescent, HMI etc)? How large an area are you shooting? Does it include the building interior, or is it bounded by the backdrop you are providing? What f-stop do you expect to get from your lights? What is the highest sync speed for your camera or lens?

    Alternatively you could gel your lights to get close to the fluorescent lights - that is not ideal, but it can be done. You would need to know what tubes they use, or borrow a colour meter (unless you have one), or estimate then fine tune with a digital camera. You would also need a modest selection of 'plusgreen' (ie green) gels and possibly a few strengths of CTO (orange) or CTB (blue) gels to make adjustments with. Knowing what kind of tubes they use, and what sort of lights you use will indicate what kind of gels to get.

    For reference, though it probably doesn't apply in this case, another way (there are a number of possibilities) would be to gel the tubes that are affecting the shot. You don't need to pin anything to the walls, just wrap the tubes that are affecting the shot in a strip of 'minusgreen' (ie magenta) gel, possibly with some colour temperature correction as well. Or wrap them in ND gel - but remember that the gels will turn light into heat.

    Best,
    Helen
     
  4. wildmaven

    wildmaven TPF Noob!

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    Helen, thanks for all the suggestions!

    To answer your questions: I don't normally use a flash, preferring to use the studio flourescents that I have. The area includes only the backdrop area, which will either be white or black muslin. My usual f-stop from my lights is adjustable. I usually can get anywhere from 1.4 to 7.8, though most of the time it's in the 2's and 3's.
     
  5. Helen B

    Helen B TPF Noob!

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    "I usually can get anywhere from 1.4 to 7.8, though most of the time it's in the 2's and 3's."

    Aha. Here are some starting suggestions for balancing a daylight source to existing fluorescents:

    Cool White 5700 K: plusgreen
    White 4300 K: ¼ CTO with plusgreen
    Warm white 3600 K: ½ CTO with plusgreen

    These gels go over the daylight source.

    Plusgreen is equivalent to CC 30 G - this is a general purpose correction filter for adding green to tungsten or daylight sources to balance with normal fluorescents. High quality, modern fluorescents need less (½ plusgreen = CC 15 G; ¼ plusgreen = CC 075 G), very bad ones need more (CC 40 G). You can also get 1/8 plusgreen.

    Overpower the existing lights as best as you can (I know that may be difficult). If it is possible to remove the offending tubes temporarily, then do so.

    To assess how much of a problem you have: Measure the incident light from the existing fluorescents, and from the existing fluorescents plus your lights. Compare digital photos of an underexposed white card taken under the two different light sources (or use a colour meter).

    If you have to live with a significant amount of light from the existing fluorescents: to avoid strange colour casts in the shadows modify either your lights or the existing lights so that they are a reasonably close match. As I mentioned in my previous post, 'minusgreen' or magenta (CC 30 M etc) filters would be used over the existing fluorescents. Balancing your lights to the existing ones may be the easiest way, but it is often not the best way in terms of colour fidelity.

    Sorry this is so rushed and incomplete. I'll try to add more information later.

    Good luck,
    Helen
     

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