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alireza852019
alireza852019
Participating Frequently
March 28, 2019
Answered

18% gray card color code in photoshop

  • March 28, 2019
  • 4 replies
  • 20552 views

Hi

Anybody knows the exact color code of 18% gray card in professional photography (which is used in custom white balance)?

So please give me that color code in photoshop (in HSB).

Thanks.

This topic has been closed for replies.
Correct answer D Fosse

Only applicable for Lab, not RGB or HSB - which is not a color space, but a generic color model, derived from RGB. You'd get very different numbers in sRGB, Adobe RGB and ProPhoto - and so you'd also get different HSB numbers.

In any case, the traditional 18% card isn't used much now. The standard tool today is the ColorChecker, which has standardized Lab numbers. These can be translated into sRGB/Adobe RGB/ProPhoto. This file is sRGB, just convert and read out in Photoshop to find numbers for other color spaces:

4 replies

D Fosse
Community Expert
D FosseCommunity Expert
Community Expert
March 28, 2019

Yes, of course: it is applicable for RGB, as long as the RGB space is specified. Clumsy phrasing on my part above.

But "HSB" doesn't exist except as a derivative of an RGB space, which has to be defined.

    G
    G_Hoffmann
    Inspiring
    March 28, 2019

    A gray card doesn't have the color gray (might be surprising).

    Gray card - Wikipedia

    It has a reflectance spectrum which is flat in the region of visible light

    and the reflectance factor is 18%.

    The reflected light has the spectral distribution and therefore the color

    temperatur of the illuminating light. Thus illuminant D50 reflects D50

    and illuminant D65 reflects D65. That's "neutral".

    Then, the color under D50 in Lab is 50,0,0 and the color under D65 in

    sRGB is 119,119,119.

    Both grays appear as equal, if the observer is adapted to the respective

    illumination.

    The short answer: the color in sRGB is 119,119,119

    Best regards --Gernot Hoffmann

    D Fosse
    Community Expert
    D FosseCommunity ExpertCorrect answer
    Community Expert
    March 28, 2019

    Only applicable for Lab, not RGB or HSB - which is not a color space, but a generic color model, derived from RGB. You'd get very different numbers in sRGB, Adobe RGB and ProPhoto - and so you'd also get different HSB numbers.

    In any case, the traditional 18% card isn't used much now. The standard tool today is the ColorChecker, which has standardized Lab numbers. These can be translated into sRGB/Adobe RGB/ProPhoto. This file is sRGB, just convert and read out in Photoshop to find numbers for other color spaces:

    c.pfaffenbichler
    Community Expert
    c.pfaffenbichlerCommunity Expert
    Community Expert
    March 28, 2019

    You forgot to mention which RGB Space you are talking about.

    Edit: HSB is not like Lab or some other device independent color space.

    HSL and HSV - Wikipedia

    And have you done a web search?

    Middle gray - Wikipedia

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