Problems with inconsistent White Balance?

Discussion in 'Pentax' started by ffrowe, Jan 22, 2007.

  1. I own a Pentax *ist DS.
    Lately I've been seeing strange behavior related to white balance (WB).
    For example, with the camera set to the tungsten WB setting, if I take several
    photos of the same object in succession, I end up with a variety of color
    casts. One photo will be too warm, the next too cool, the next "just right",
    etc. These are not subtle variations; they are substantial.

    I first noticed this problem with the tungsten setting, but I was able to work
    around the problem by doing a Manual WB adjustment.
    But now I'm starting to see the problem even with Manual WB.

    Has anybody else had this problem??
    Any idea what's going on, and what I can do about it?
     
  2. This is due to the exposure time. Fluorescent light (tungsten) color temperature varies with the AC alternances. <br>To avoid or at least minimize it as much as possible, the exposure time must be a multiple of a half alternate, i.e. 1/100 for 50Hz AC in Europe and 1/120 for 60Hz AC in US.<br>
    Example of good exposure times (for Europe 50 Hz):<br>
    1/100, 1/50, 1/33(not existing on many bodies), 1/25, 1/20, 1/16, ...<br>
     
  3. <<Fluorescent light (tungsten) color temperature>>

    Just to be clear, Tungsten lighting is not the same as Fluorescent lighting. A Tungsten WB setting is the same as Incandescent which is the "traditional" filament-based light bulb.

    However, Renato is correct: you're capturing the flicker of fluorescent lighting based on a 60 Hz cycle.
     
  4. I've seen it while shooting basketball indoors. Caused some head scratching until I looked it up here.

    And I agree, the white balance modes seem utterly useless to me. I always have to do a manual adjustment indoors, the presets never work.
     
  5. Really? I've never heard of such a thing. (How is it that I avoided this problem for the first 18 months that I owned the camera?!) I'm attaching a series of five photos to illustrate the problem. Note the changing colors of the floor and the back wall. All of these were taken at 1/350 sec, f/2.8, ISO 3200, with White Balance set to Tungsten. Do you really think it's caused by what you've described above?
    00JdAj-34558884.jpg
     
  6. Frank this is very true. The light comes in waves which change color.

    Go to sportshooter.com and ask about shooting under sodium vapor lights if you don't believe us. Sodium vapor is most often found in stadium lighting, among other places.

    Sodium vapor runs on a similar hertz and is the worst because even with a custom WB you can catch it between cycles.

    The best advice, and not my preference, is to shoot RAW in tough ligting (indoors, stadiums, mixed lighting) and forget about the WB till post processing.

    SInce you might miss the cycle anyway even if being careful you are better off just setting WB to daylight and batch adjusting at the end of the day.

    This is what I do for sports. Then I fine tune the keepers.
     
  7. thanks for all your collective help! so... when I took photos at the same gym a week later (see below) and my colors were more consistent, it probably wasn't because I was using a custom WB, but instead was because most of my photos were taken at 1/250 sec (a slower shutter speed)? Here's the most illuminating (no pun intended) information I found at SportsShooter: http://www.sportsshooter.com/message_display.html?tid=20873 Speaking of custom WB, no one has specifically stated this, but I'm assuming that it's important to set your shutter speed to 1/60 or slower when setting the WB, to capture the full cycle of the lighting. (am I right?)
    00Jddz-34568884.jpg
     
  8. "no one has specifically stated this" ?
    Did you read my very first answer?
    It states exactly this thing with the same words.
     
  9. Frank,

    Yep, no matter what you do, under flourescent lighing or sodium vapor, you will never be happy with the initial outcome. even pro's using $7000 cameras have ths same issues.

    Custom WB can help a lot but only if you are using a shutter speed that captures the full cycle. or you hit the cycle right every time.

    as i mentioned, shoot raw, batch correct for basic editing, and then custom edit the keepers. it's the only way to beat the WB issue with a digital camera, and luckily it cost you nothing.
     

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