Re: Standby...
Re: Standby...
- Subject: Re: Standby...
- From: "Cedric Briscoe" <email@hidden>
- Date: Fri, 9 Jul 2004 14:46:39 -0400
Wishful thinking [on the info from Epson]
But! Here is a tidbit:
Q: What is the Yule-Nielsen factor for Epson's semi-matte professional media
proofing paper?
A: There really is no "correct" Yule-Nielsen factor (Editor's note: the
factor accounts for how light is scattered on paper) for any media, paper,
plate or process.
To qualify that statement, we need to better understand what the YN equation
actually does to the Murray-Davies dot area equation and how the N-factor is
calculated for any given process. (Editor's note: The Murray-Davies equation
computes a dot from density measurements.)
The Y-N equation simply adds a "fudge-factor," correctly called the
N-factor, to the M-D equation. This exponent adjustment to the M-D equation
simply adjusts the result of the dot area equation - much like a plate
compensation curve changes the dot gain result on press.
If you want your instrument (densitometer or spectrophotometer) to read a
particular dot pattern differently than it does now, simply change the
N-factor and the numbers reported by the instrument will change.
The "zero" state of the N-factor is 1.0 because it is an exponent in the
equation. (Raising a number to the power of 1 in effect does nothing.) If
you increase the N-factor, the densitometer's dot area values will go down.
If you decrease the N-factor, the densitometer's dot area values will go up.
The N-factor is primarily used to make a densitometer react like a
planimeter. It will make the instrument measure a visual dot area more like
a mechanical dot area. Again, it does this based upon a user adjustment.
The way you determine the N-factor is to visually determine what you think
is a mechanical 50 percent dot area on your plates or paper. You then adjust
the N-factor in the instrument until it reads this area as 50 percent.
(Editor's note: You can use a CCD-based plate reader or planimeter.)
Determining what the N-factor should be for the Epson semi-matte paper
really begs the question: "What are you trying to do?" If you are
attempting to read dot gain on an inkjet proof as compared to a press sheet,
do not use an N-factor.
In other words, use the same N-factor for both the proof and the press
sheet.
If you are really attempting to read a mechanical dot on the inkjet media,
follow the instructions above. You must determine what you think a 50
percent dot is on the proof, then adjust the N-factor until the instrument
reads it as 50 percent.
- Mike DiCosola
email@hidden
Cedric Briscoe
Treetop Publishing, Inc.
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