Mercury Vapor White Balance

Discussion in 'Canon EOS' started by gotdesign01, Jan 30, 2008.

  1. In a couple weeks I will be taking some portraits of a family gathering that
    will take place in a hall with mercury vapor lighting. Does anyone know a good
    custom WB setting on a EOS 10D for use with MV lights?

    Please e-mail me at GotDesign01@gmail.com

    Thanks much.
     
  2. Custom white balance taken off a white or grey card is always the most accurate method for shooting JPEGs

    Mercury lights don't have a continous spectrum and can't easily be assigned a color temperature. Modern designs have a phosphor coated envelope which can help, though they still tend to be biased towards the blue.

    I'd shoot RAW (or RAW+JPEG) and work on the correction in RAW post exposure processing.
     
  3. Like Bob said, I assume they will change WB with the mains frequency like other fluorescent lights, so a tripod and shutter speed of 1/50 or 1/60 (whatever your mains frequency is) might be advised.
     
  4. Also, if you want E-mail notification, I believe there's a link you can click at the bottom of this thread.
     
  5. The other tactic is to drown out the mercury lights with flash. That's probably reasonably easy to achieve for individuals and couples, but requires a lot of light once you get up to groups and tables. You will want to avoid mixed lighting. If at all possible try to get into the venue and run some tests ahead of time. If you have a good selection of flash gels you may be able to supplement the venue lighting with flash that has been gelled to give a reasonable match, but it could be tricky. These spectra give you an idea as to why:

    http://ioannis.virtualcomposer2000.com/spectroscope/amici.html#1p
     
  6. Either use a gray card to custom your white balance, or if possible get your hands on an Expo Disk. I do a lot of shooting in school gyms, and it is a lifesaver.
     
  7. Hi Aaron,

    Definitely set a custom white balance.

    Don't try using straight flash as a FILL along with the mercury vapor ambient lighting. The flash will not match the custom white balance you've set, and you'll get strangely mixed light as a result. It's impossible to set a custom white balance for ambient + fill flash, since the ratio of one to the other will change with every different shot.

    Instead, if you need to bounce extra light onto your subjects or to open up shadows, try one or two silver (neutral) reflectors. That way any fill light you use is the same color as the main lighting from above.

    Or use FULL flash, as suggested by Mark.

    Alternative would be to gel your flash. Gels can be used this way to adjust your flash's fill output to closely match ambient light. But it's tricky to do with mercury vapor because they vary in color bulb to bulb and there are a couple different approaches to color correction. In the past I've used 60 to 80 Magenta gel combined with a 15 to 20 Cyan gel or just used a 50 to 60 Red gel. Again, the exact gel needed varies under differing mercury vapor light, so you'd have to experiment a little in advance, take some test shots to see what actually works best in the particular situation where you are shooting.

    Also make a few reference shots early on, with a white or gray prominent card in them. Later you can use that target in Photoshop (or whatever), to get finer color correction.
     

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