Hi, In my opinion, you should simply make a 30% tint of your pantone then just measure the sample (printed or viewed) and get Lab values or maybe I'didnt understand your question (sorry).
Geetings Simon [EMAIL PROTECTED] napisał: >Send Lcms-user mailing list submissions to >[EMAIL PROTECTED] > >To subscribe or unsubscribe via the World Wide Web, visit >https://lists.sourceforge.net/lists/listinfo/lcms-user >or, via email, send a message with subject or body \'help\' to >[EMAIL PROTECTED] > >You can reach the person managing the list at >[EMAIL PROTECTED] > >When replying, please edit your Subject line so it is more specific >than "Re: Contents of Lcms-user digest..." > > >Today\'s Topics: > > 1. Re: over white color clipping (Gerhard Fuernkranz) > 2. Tinting of Pantone Colours (Glenn Wilton) > >--__--__-- > >Message: 1 >Date: Sun, 19 Sep 2004 00:20:19 +0200 >From: Gerhard Fuernkranz <[EMAIL PROTECTED]> >To: Marti Maria <[EMAIL PROTECTED]>, Lcms Liste > <[EMAIL PROTECTED]> >Subject: Re: [Lcms-user] over white color clipping > >Marti Maria schrieb: > >>The computations are done in 16 bits of precision, unless of course, you recompile >>the engine with USE_FLOAT. But even in this case temporary results are stored in 16 >>bits. This is enough for most imaging operations were visual accuracy is about 11 >>bits at most. >> >Hi Marti, > >this number corresponds with an experiment I\'ve done recently: > >I selected 5000 colors, distributed approximately evenly within the sRGB >gamut. Then I computed the gradients dXYZ/dE94 for each color. The >lowest value I got was 0.023, which is approx 100/4347. This means, in >the worst areas of the sRGB gamut, an dX, dY or dZ step of 0.023 >corresponds to one de94 unit, and in all other areas, even a larger XYZ >step is necessary to become noticeable. Log2(4347) = 12.1, thus approx. >12 bits (in linear XYZ space) are sufficient, in order that (in the >worst case) the size of a one LSB step drops below 1 dE94 unit. Since >the quantization error is only 1/2 LSB, we need even one bit less, if >our goal is a max. quantization error below 1 dE94. > >For 4750 out of the 5000 considered colors (i.e. 95% quantile), the >gradient was above 0.079, which is 100/1265, corresponding to 10.3 bits, >to achieve a one LSB step size of 1 dE94. Thus 9.3 bits are sufficient >for 95% of all considered colors, if I want the quantization error drop >below 1 dE94. > >So yes, with 16 bits of precision for the internal computations of the >transform there should be still some room in the "normal" case, where >the image is already normalized to the desired white point luminance, >before the transform is applied. > >But it looks like people also desire to apply transforms to HDR images. >So if one applies a transform to an image, and THEREAFTER wants for >instance to scale up the luminace of the transformed image by e.g. a >factor of 1000, in order to extract very dark areas of the HDR image, >then he has rather lost with a 16-bit transform, even if the original >HDR image (before the transform) would have contained enough accurate >shadow detail information for the desired luminance upscaling. > >Regards, >Gerhard > > > > > >--__--__-- > >Message: 2 >Date: Sun, 19 Sep 2004 11:25:25 +1200 >From: Glenn Wilton <[EMAIL PROTECTED]> >To: Lcms Liste <[EMAIL PROTECTED]> >Subject: [Lcms-user] Tinting of Pantone Colours > >A Question for the group > >If I have a pantone colour measured as say Lab 30 ,10, -30, and I want to >calculate a 30% tint of this colour what\'s the correct way to do this? > >Do I do a linear interpolation towards a theoretical white of Lab 100,0,0 or >do I use a D50 White or a measured Lab white from the origional paper? > >Or its there another method I should be using? > >Glenn Wilton >> [EMAIL PROTECTED] < > > > > > > >--__--__-- > >_______________________________________________ >Lcms-user mailing list >[EMAIL PROTECTED] >https://lists.sourceforge.net/lists/listinfo/lcms-user > > >End of Lcms-user Digest > ------------------------------------------------------- This SF.Net email is sponsored by: YOU BE THE JUDGE. Be one of 170 Project Admins to receive an Apple iPod Mini FREE for your judgement on who ports your project to Linux PPC the best. Sponsored by IBM. Deadline: Sept. 24. Go here: http://sf.net/ppc_contest.php _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user
