From: poynton@poynton.com (Charles Poynton) Subject: Re: Density and Lightness Date: 15 Jul 1999 00:00:00 GMT Message-ID: References: <19990715012943.23418.00000537@ng-fy1.aol.com> X-Complaints-To: abuse@home.net X-Trace: news2.rdc1.on.home.com 932052888 24.112.223.36 (Thu, 15 Jul 1999 08:34:48 PDT) Organization: Toronto, ON Canada, +1 416 486 3271 X-No-Junk-Mail: yes (Do not put me on any mailing list; send no junk mail.) NNTP-Posting-Date: Thu, 15 Jul 1999 08:34:48 PDT Newsgroups: sci.engr.color In article <19990715012943.23418.00000537@ng-fy1.aol.com>, fotodave@aol.com (FotoDave) wrote: > Is there a simple equation or equations to convert reflective density > (from a densitometer) to lightness [CIE L*]? For density D in the range 0 to 2, Lstar = 116 * power(10, -D/3) - 16 That is, take one third of the density value, negate it, raise 10 to that power, multiply by 116, then subtract 16. This will give you L* with respect to a white reference at D = 0. You'll have to make some adjustments of you want L* with respect to some other Dmin. For D greater than 2, you're on your own. C. -- Charles Poynton Poynton Color FAQ, www.poynton.com (MODIFIED 13 Feb 2003)