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White Balance and Grey Cards

Discussion in 'Digital Image Editing & Printing' started by Craig20264, Sep 25, 2017.

  1. Craig20264

    Craig20264 Well-Known Member

    When shooting product/portrait etc. photography, does anyone use a white balance grey card in one of the shots, to later accurately set the white balance in PS?
    Also is the grey card used for white balance, the same as the 18% grey card used for metering? I've read conflicting articles, with some saying they are one of the same, and others disagreeing, and that they are in fact, different shades of grey.
     
  2. spinno

    spinno Well-Known Member

    There are more than 50 shades of grey, in fact 256 ranging from pure white to jet black. I don't include a grey card or such in portraits as I don't do indoor stuff except on rare family get-togethers where a record is more important than exposure.
    The only time that I set my own WB is when I'm shooting IR on the converted K-01.
     
  3. PeteRob

    PeteRob Well-Known Member

    Once, to demonstrate to my son how it was done. Ought to do it more often as the results surprised me greatly. It was in a wood where the colour of light through the canopy can be quite strange. In principle it is best to use a conventional grey card. If your exposure was preset correctly a white card would be close to white (255,255,255) and offer little hope for balancing colour. If the exposure is not preset then the camera on autoexposure will see the white card as grey and correction will work. Use a grey card and you can get both colour balance and exposure.
     
    Craig20264 likes this.
  4. EightBitTony

    EightBitTony Well-Known Member

    When you're setting white balance with an automated tool, you want to know that the thing you're picking should have equal amounts of R, G & B, but doesn't. The tool can then work out how much R, G or B to add/subtract to make it neutral. So an 18% grey card is fine, as is any card that is truly grey of any shade (i.e. no tint).
     
    Craig20264 likes this.
  5. GlennH

    GlennH Well-Known Member

    I haven't used a grey card for metering since my film days, and while some of these methods may still be valid (ETTR as well), haven't they been somewhat obsolesced by improvements in digital image quality over the years? I've used an X-Rite ColorChecker white balance card for occasional copying of old newspapers, where I wanted to preserve the aged yellowing of the paper. Theoretically, I could've taken the WB reading from the newspaper itself, but with different results. A neutral tone in the image is the key component of auto-colour tools in Photoshop and other editors, and without it there's no objective way to neutralise a colour cast. That said, experienced portraitists may well know the expected ratio of RGB values in skin tones.
     
    Craig20264 likes this.
  6. Terrywoodenpic

    Terrywoodenpic Well-Known Member

    Including a grey card in a shot is only helpful up to a point.
    Unfortunately the angle at which it is placed has a massive effect on the result.
    like any plane surface it will reflect light back to the camera from mainly one direction. if that is the sky it will be mostly sky colour if it is a canopy of leaves it will be another... and so on. However the scene as a whole will be illuminated by all of these.
    As I shoot raw there is no point at all in setting any particular white balance, as raw files do not have a colour balance.
    I find it far better to set it during processing. I do this first using the "As set by camera" then using the picker on any object that I want to be portrayed as grey.
    By flicking around such points, I can quickly establish a balance the "Looks" right. This is far more effective than trying to use the Sliders in Lightroom or Photoshop.
     
    Bazarchie, Craig20264 and Roger Hicks like this.
  7. Roger Hicks

    Roger Hicks Well-Known Member

    Thanks Terry. I was going to try explaining the same thing but I do not think I could have done so as clearly and concisely, so I wimped out. The only catch is when there is no neutral grey (including most "whites" and "blacks") e.g. as in several pictures in http://rogerandfrances.eu/photography/accurate-colour, where I also challenge the objectivity of colour representation.

    Cheers,

    R.
     
    Terrywoodenpic likes this.
  8. El_Sid

    El_Sid Well-Known Member

    Has anyone used one of those white balance filters you sometimes see advertised - the semi-translucent ones you put over the lens and then set the white balance directly with the filter on or take a picture with it on and set the white balance from that? They look like they might be an option rather than cards but I wonder if they are that reliable.
     
  9. Terrywoodenpic

    Terrywoodenpic Well-Known Member

    when pointed in the direction of the scene all they do is make the assumption that all the colours in the image will add up to a neutral grey. in some general shots it can work quite well. But they are easily fooled by a preponderance of one colour in the scene.
    They are also be used by pointing toward the camera, like an incident meter. to measure the light falling on the subject, which can give rather more consistent results. However they suffer the same difficulties in mixed light as any other method.
    They give a rather expensive approximation, but probably no better than the camera will set unaided.
     
  10. Roger Hicks

    Roger Hicks Well-Known Member

    Dear Nigel,

    Yes. I have one. They are good incident light meters -- but as Terry pointed out in Post 6, that's not much use under mixed light, e.g. in woodland.

    This brings me back, as so often, to a simple injunction:

    DO NOT SEARCH FOR MORE PRECISION THAN EXISTS IN A SYSTEM.

    Cheers,

    R.
     
  11. dangie

    dangie Senior Knobhead

    Or..... If it looks right.... It is right.
    I don't really worry beyond that.
     
  12. El_Sid

    El_Sid Well-Known Member

    I thought that might be the case- which is why I never splashed out on one.

    As for your injunction there's someone in another thread here who could possibly do with getting to grips with the concept...;)
     

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