- From: Pierre-Anthony Lemieux <pal@sandflow.com>
- Date: Sun, 3 Sep 2017 10:00:18 -0700
- To: Peter Occil <poccil14@gmail.com>
- Cc: public-colorweb@w3.org
> Is it true that the "sRGB black point" (what sRGB defines as black) has a luminance of 0.2 cd/m^2 (absolute Y = 0.2) > rather than 0 cd/m^2 (absolute Y = 0, the start of the absolute XYZ scale)? ISO 61966-2-1 [1] specifies that [X Y Z] = [0 0 0] yields [R G B] = [0 0 0] (see equation 8). Furthermore, quantized 8-bit R8 = 255 R' , where R' is non-linear R, (see equation 4) and R' = 12.92 R when R' < 0.04045. (see equation 5) ... so R8 = 0 when [X Y Z] = [0 0 0] , with the same reasoning applying to G8 and B8. Let me know if I got this wrong. Best, -- Pierre [1] https://webstore.iec.ch/publication/6169 On Sun, Sep 3, 2017 at 5:05 AM, Peter Occil <poccil14@gmail.com> wrote: > While I'm at it, that document contains a very questionable statement about > the "black point" of sRGB, suggesting that the "black point" has a "veiling > glare luminance" of 0.2 cd/m^2 (and indeed that suggestion appears further > in some of the formulas in that document). Is it true that the "sRGB black > point" (what sRGB defines as black) has a luminance of 0.2 cd/m^2 (absolute > Y = 0.2) rather than 0 cd/m^2 (absolute Y = 0, the start of the absolute XYZ > scale)? > > > > On 09/02/2017 03:28 PM, Peter Occil wrote: >> >> I'm aware of the following document posted on the W3C Web site: >> >> https://www.w3.org/Graphics/Color/srgb >> >> I find it very useful as a reference, but: Where did this document come >> from? Who were its authors? When was it posted? I couldn't find it linked >> anywhere on the W3C site except on a mailing list message (ref. 1). >> >> Ref. 1. https://lists.w3.org/Archives/Public/www-style/2016Sep/0061.html >> > >
Received on Sunday, 3 September 2017 17:01:09 UTC