Re: Reversing the Murray Davies Dot Gain Equation
Re: Reversing the Murray Davies Dot Gain Equation
- Subject: Re: Reversing the Murray Davies Dot Gain Equation
- From: <email@hidden>
- Date: Tue, 19 Sep 2006 09:42:46 -0400
Hello Lee,
Try this:
Ds = Dp - log(1 - ((100 - 100 * 10^(Dp - Dt)) / Da) )
where
Ds = Dsolid
Dp = Dpaper
Dt = Dtint
Da = Dot Area in percent, i.e. 75 for 75%.
You may need to calculate Dot Area from Dot Gain:
Dot Gain = Dot Area - N
where N is the nominal tint, in percent, i.e. 50 for 50%.
You can also find the (non-inversed) equations, and others
related to density here:
http://www.babelcolor.com/download/BabelColor_Help.pdf
on pages 190 plus.
Have fun!
Danny Pascale
email@hidden
www.BabelColor.com
On Tue, 19 Sep 2006 09:39:54 +0100
Lee Badham <email@hidden> wrote:
Hi,
The Murray Davies equation is used to calculate the dot
area based on the density of the paper, dot and solid
areas.
I've been trying to reverse the equation so that I can
calculate the solid density, if I know the dot density
and the percentage, but keep getting math errors (log of
a negative number).
The Murray Davies equation is
D=100*(1-(10^(D0-Dn))/(1-10^(D0-D100))
Where D=Dot percentage
D0 = density of paper
D100 = solid density
Dn = density of area read
I'm trying to change the equation around to calculate
D100, if I know D
The equation I came up with (which doesn't work) is
D100=D0-Log10((1-((1-10^(D0-Dn))*100/D)
D has been calculated by using the XYZ values for the
colour.
I'm getting a headache just looking at these equations
now. Hope someone can help
For an easier display of the Murray Davies equation
please visit http://www.brucelindbloom.com and click on
Math, then near the bottom of the page, there's a link
to the Dot Gain page.
Lee Badham
Bodoni Systems Ltd
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