Custom WB using 3 color cards

Started Jul 5, 2013 | Discussions
er3
er3
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Custom WB using 3 color cards
Jul 5, 2013

So I was thinking about getting an 18% gray card to set custom WB. BUt saw these 3 color WB cards. Are they used the same way? As in you zoom in, take a pic & then set the custom WB in camera? Or are these just for post processing?

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Mark Scott Abeln
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Re: Custom WB using 3 color cards
In reply to er3, Jul 5, 2013

er3 wrote:

So I was thinking about getting an 18% gray card to set custom WB. BUt saw these 3 color WB cards. Are they used the same way? As in you zoom in, take a pic & then set the custom WB in camera? Or are these just for post processing?

If the three colors — can I assume they are white, gray, and black? — if they are neutral, then you can use one for white balance. I’d use the white one.

The way the card is intended to be used is this:

  • Take a photo with the card in the image, making sure that the white part is not overexposed, and the black part is not underexposed. Be sure that the card is facing the camera directly, and has the same lighting as the main subject.
  • Without changing anything in the scene, without moving the camera or subject or lighting, nor changing the exposure or white balance, take another photo of your subject without the card.
  • In post processing, use curves to force the white part to be near pure white — maybe an RGB value of (240, 240, 240). 
  • Do the same to the black part, setting it to about (25, 25, 25). 
  • And do likewise to the gray part, setting it to about (128, 128, 128).
  • These are guesses on my part: your manual might recommend other values.
  • Apply those same curves on the photo you took without the card in it. You should get a nice tonality and white balance on your image. 

This is one of those calibration steps which might be critical for good work, but may become less necessary as you gain experience.

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er3
er3
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Re: Custom WB using 3 color cards
In reply to Mark Scott Abeln, Jul 5, 2013

Mark Scott Abeln wrote:

If the three colors — can I assume they are white, gray, and black? — if they are neutral, then you can use one for white balance. I’d use the white one.

The way the card is intended to be used is this:

  • Take a photo with the card in the image, making sure that the white part is not overexposed, and the black part is not underexposed. Be sure that the card is facing the camera directly, and has the same lighting as the main subject.
  • Without changing anything in the scene, without moving the camera or subject or lighting, nor changing the exposure or white balance, take another photo of your subject without the card.
  • In post processing, use curves to force the white part to be near pure white — maybe an RGB value of (240, 240, 240).
  • Do the same to the black part, setting it to about (25, 25, 25).
  • And do likewise to the gray part, setting it to about (128, 128, 128).
  • These are guesses on my part: your manual might recommend other values.
  • Apply those same curves on the photo you took without the card in it. You should get a nice tonality and white balance on your image.

This is one of those calibration steps which might be critical for good work, but may become less necessary as you gain experience.

Thanks so much. Yes, I am referring to the black/grey/white cards. I usually try to set my custom WB in the camera & shoot RAW, which is why I was looking for an 18% grey card, but I am always trying to find ways to improve. Perhaps I'll get both.

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Canon EOS 7D Olympus OM-D E-M5
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Mark Scott Abeln
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Re: Custom WB using 3 color cards
In reply to er3, Jul 5, 2013

er3 wrote:

Thanks so much. Yes, I am referring to the black/grey/white cards. I usually try to set my custom WB in the camera & shoot RAW, which is why I was looking for an 18% grey card, but I am always trying to find ways to improve. Perhaps I'll get both.

You’re welcome. Be aware that the classic 18% gray card was originally intended as a method of achieving a standard exposure with film — which may not really give you a good exposure, since  digital images typically don’t have much exposure headroom and it is really easy to overexpose.

Some 18% cards — I’m thinking of the Kodak card — also aren’t photographically neutral, and so aren’t suitable for doing a good white balance. Usually a brighter card, guaranteed to be neutral, is a better bet for doing white balance.

 Mark Scott Abeln's gear list:Mark Scott Abeln's gear list
Nikon D200 Nikon D7000 Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF Nikkor 50mm f/1.8D Rokinon 85mm F1.4
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