Re: Testing for Dmax
Re: Testing for Dmax
- Subject: Re: Testing for Dmax
- From: Eric Chan <email@hidden>
- Date: Sun, 21 Sep 2008 19:38:07 -0700 (PDT)
Edmund,
In general your spectro will give you L* values.
Easy way: go to Bruce's Companding Calculator (see link below), enter your L* value and click the "L*" button. The density is then computed in the field immediately below. Reflectance is computed in the "Y" field above (e.g., L* = 50 corresponds to about 18% reflectance, as you know). L* = 9 is roughly a d-max of 2, corresponding to the older UltraChrome printers (e.g., Epson 2200) from Epson. L* = 5 or below is now possible with the newer printers using Photo Black. I often measured around L* = 2 or 3 when printing on PK papers via the Advanced B&W Photo driver on the Epson K3 or K3 + VM models. L* is more typically in the 16--20 range when printing with Epson K3 or K3 + VM on matte papers, which is consistent with the results reported in the original post.
http://www.brucelindbloom.com/CompandCalculator.html
If you want the math, go here:
http://www.brucelindbloom.com/Eqn_Lab_to_XYZ.html
Once you compute Y from L*, then density is just -log (base 10) of Y.
Eric
--- On Sat, 9/20/08, edmund ronald <email@hidden> wrote:
> From: edmund ronald <email@hidden>
> Subject: Re: Testing for Dmax
> To: "'colorsync-users?lists.apple.com' List" <email@hidden>
> Date: Saturday, September 20, 2008, 5:50 PM
> btw, what's the quick way (formula) to get standard
> density values
> from a spectro ?
>
> Edmund
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