Setting white balance with a gray card

Discussion in 'Lighting and Hardware' started by adamhiram, Jun 1, 2017.

  1. adamhiram

    adamhiram No longer a newbie, moving up!

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    I’ve used different methods of setting my white balance over the years. Sometimes auto wb in the camera or Lightroom’s auto wb gets pretty close, while other times I find it helpful to use Lightroom's wb eyedropper tool on something white/neutral in the photo as a starting point. Either way, I typically tweak it manually by eye on a calibrated display until it looks just right, often with vibrance set to 100% to exaggerate any color casts.

    I’ve also collected a handful of accessories used to help set white balance, and have had very mixed results with them. I’m not sure if I’m using them wrong, if they are defective, or if that’s just the nature of trying to take a shortcut.

    In the test shot below, I have the following items that should be usable for setting white balance. The background is a Westcott 40” white reflector. In the center is a Lastolite 12” collapsible gray card, and lastly, I threw in some cheap Adorama gray/white/black cards that I’ve had in my bag for as long as I can remember.

    For the test shot, the camera was perpendicular to the reflector and gray cards, and a soft box was used as the only light source, about 45 degrees off-axis directly in front of the camera (top of frame). This was shot in a dark room with no ambient light.

    [​IMG]
    20170601-DSC_2571a


    Here are the settings I got without the gray cards:
    • As shot (camera auto wb): 6550 -1
    • Lightroom auto wb: 7500 +1
    • Manually set wb by eye: 7300 +2 (this is the current wb setting in the image above)
    Next I used the eyedropper tool in Lightroom on the various accessories in the photo. To avoid any anomalous readings, I took 8 samples each and use the average.
    • Large white reflector: 7175 +2
    • Collapsible gray card: 7540 +4
    • Small gray card: 6930 +3
    • Small white card: 7730 -6
    • Small black card: 7620 -2
    Any thoughts on why I am seeing different results for different cards? In theory, every surface in this photo should be color neutral and is illuminated by the same single light source. Is it likely that some of these are not as color-neutral as I would believe, or am I using them wrong? Or is a color temp difference of 500-600K really not something to stress over?


     
  2. Ysarex

    Ysarex Been spending a lot of time on here!

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    Yep.

    white_balance.jpg


    Most people can't see a color temp difference of less than 200K. So 500K is still pretty minor. I stopped buying commercial WB cards etc. I still have and use an X-Rite Passport, but to use as a WB reference I just cut rectangles out of white Styrofoam food trays and take out containers. I stick one in every camera bag and jacket pocket and there's a stack of new ones on my desk ready to replace one that gets dirty -- consistent and at least as good as the ones you have to pay for -- actually better.

    wb_card.jpg

    Joe
     
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  3. Christie Photo

    Christie Photo No longer a newbie, moving up!

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    If I'm not shooting candids of the kids, I ALWAYS shoot a grey card at the start of each situation. If I change the lighting, I shoot another card. I've been doing this since the start of digital. (Before then, I would read a card for exposure.) Yes... I do see slight variances, but usually I keep with the color balance as shot.

    Now... this is for commercial shots, when I need absolutely correct color. I don't always want absolute correct color for portraiture. It's seldom my aim to depict people as they are. Portraits serve an entirely different purpose. A bit of warming is desirable.

    -Pete
     
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  4. adamhiram

    adamhiram No longer a newbie, moving up!

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    Here is my question then - am I using this gray card wrong, is it defective (strong color cast), or is this just not a reliable way of setting white balance? To be clear, I am able to set white balance correctly through other means, whether it is by eye in Lightroom, or by sampling something color-neutral in a photo. I'm just curious why I am not getting remotely usable results from a gray card.

    The following examples include a test shot I took for another post, with the white balance set to what I believe is correct (top right). The white balance is set to 7000k +2, whereas sampling from the primary light source (top left) gives me 7200K +2 - pretty close. However, simply holding up a gray card perpendicular to the camera and lit by the exact same light source (bottom left), I get a white balance of 8525K +2. This is off by about 1500K from what I determined to be ideal, and is too warm as can be seen in the bottom edit (bottom right).

    Any thoughts on how I can actually get more value from a gray card? I certainly don't need to use one, but I'd like to understand why I'm not getting usable results with it.

    [​IMG]
    whitebalance-examples
     
  5. Ysarex

    Ysarex Been spending a lot of time on here!

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    Looks like you've figured it out for yourself -- that lastolite fabric card is grey blue and you're not using it wrong. It's not color neutral. That doesn't mean you can't use it but you'd have to calculate a compensation factor for it. I don't want to sound flippant but get a cup of coffee and your problem is solved.

    [​IMG]

    Joe
     
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  6. adamhiram

    adamhiram No longer a newbie, moving up!

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    That's really too bad, I liked the idea of a collapsible gray card that is big enough to be usable, but small enough to throw into any bag. The strange thing is that in controlled tests it seems to be off by about -500K, while in real world scenarios like the one above, there's a -1500K shift. Perhaps it just has an odd reflectivity. Who knows.

    On the contrary, if there is one thing people can take away from this thread, it's that white styrofoam is almost always pure neutral white, makes a great gray card if you underexpose it, and can be used as DIY reflectors in larger sheets. I have a stack of 30" square sheets left over from replacing a glass shower door that I use regularly at home, they just aren't convenient to travel with.

    So to summarize:
    • Adorama credit card sized gray card: too small to be useful, slight warm cast.
    • Adorama credit card sized black/white cards (come with gray card): might be useful for setting black/white points, but not color-neutral at all
    • Lastolite collapsible gray card: great concept, but not 18% gray (darker), and not color-neutral (off by -500 to -1500K). Interestingly enough, the white side was a little better, but still had a slight blue cast.
    • Westcott 5-in-1 reflector: very close to pure white, actually pretty useful as a makeshift gray card if it's not currently in use as a reflector, but also doesn't fit in a camera bag.
    • White styrofoam sheets (or coffee cup!): pure white, works nicely as a gray card, just not as compact as an actual gray card.
    Or to set WB manually, DIYPhotography had a nice post a few weeks ago with a simple method that is quick and easy on a properly calibrated display.
    This 3 step raw colour correction tip will fix your white balance woes - DIY Photography
     
  7. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    I've tried just about every WB gadget on the market (and have almost as many of them as I have tripods...). The ONLY two that I've found worth thinking about are (1) The white Styrofoam already mentioned, and (2) The X-Rite Colour Checker.
     
  8. Christie Photo

    Christie Photo No longer a newbie, moving up!

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    Fill the frame with nothing but the gray card. Make an exposure. Then set the camera for custom white balance and select the image of the gray card.

    I usually repeat the sequence, but that's just me.

    -Pete
     
  9. Ysarex

    Ysarex Been spending a lot of time on here!

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    That's a Canon camera specific procedure for setting a custom JPEG white balance. The OP is a Nikon user (different procedure) and I suspect is more interested in processing raw files.

    Joe
     
  10. adamhiram

    adamhiram No longer a newbie, moving up!

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    To be honest, I'm not sure if I have the ability to manually set WB in-camera with Nikon - I always shoot RAW, so it's something I typically address in post. However, the real issues here are that my neutral gray cards are not actually color-neutral, and oddly, do not even produce consistent results between shots with slight variations in lighting setup.

    I actually added "get take-out from someplace that uses white styrofoam containers" to my to-do list. :)
     
  11. Ysarex

    Ysarex Been spending a lot of time on here!

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    Go to the grocery store and for a couple bucks buy a stack of white Styrofoam disposable party plates. Lifetime supply WB reference $4.00: Amazon.com: Hefty Everyday Foam Plates (White, Soak Proof, 9-inch, 130 Count): Prime Pantry

    Joe
     
  12. table1349

    table1349 Been spending a lot of time on here!

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    When shooting sports I always use a Lastolite LL1250 and like it. Works fine, but then it is a 12% gray card, not the older 18% that Ansel Adams so loved. Most camera makers calibrate their meters towards 12% gray.

    For studio I use a WhiBal neutral white card. It is sturdier than Styrofoam and if it gets dirty I just wipe it off.
     

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