Re: Eye-One as Densitometer
Re: Eye-One as Densitometer
- Subject: Re: Eye-One as Densitometer
- From: Phil Green <email@hidden>
- Date: Wed, 05 Sep 2001 22:02:24 +0100
- Organization: LCP
"Vanderlinden, Thomas M." wrote:
>
I'm looking for hints on converting the (Lab) readings
>
one can get with the GretagMacbeth Eye-One spectrophotometer
>
of printed C, M, Y, or K to dot percentage readings
>
like one might get from a densitometer.
You can do this if you can first measure a ramp of known dot percentages
and then create a look-up table to interpolate any intermediate values.
This will work for any colour, but you do have to make the measurement
for every print condition (process+paper).
I don't know the Eye-One, but if like other GM spectros it will give you
a density reading you can do an approximate conversion to dot area using
the Murray-Davies equation:
A = (1-10^-Dt)/(1-10^-Ds) where A is the dot area, Ds and Dt the density
of the solid and halftone respectively.
The problem with this method is that you have to correct it for light
scatter in the paper to make it reasonably accurate.
--
Phil Green
Colour Imaging Group
School of Printing and Publishing
LCP
Elephant and Castle, London SE1 6SB
Tel: +44 020 7514 6759 Fax: +44 020 7514 6772
http://www.digitalcolour.org