Nelson Factor

[pacificiam]

Hi,


I want to knw abt Nelson factor.
Why it is use?

[gordo]

Hi,
I want to knw abt Nelson factor.
Why it is use?

When you measure dot area/dot gain on a press sheet using a densitometer you are measuring the ratio between the amount of light reflected back through a given halftone versus the amount of light collected back from a solid of the same color. The measurement includes both mechanical and optical dot gain if the dot gain measurement is taken by a densitometer using the Murray-Davies equation.

But if the densitometer calculates dot gain using the Yule-Nielson equation the answer is mechanical. The Yule-Nielson equation utilizes an n-factor to "factor" out the optical dot gain. The Murray-Davies equation is equivalent to the Yule-Nielson with n set to 1.00. The n-factor is experimentally determined by adjusting the n-factor until the densitometer reads the ‘desired value’ at a known dot percentage. Typically a 50% tone is used because it is easy to spot. You'd print a number of tone values close to 50% (e.g.45% and 55%) then use a loupe to find the tone patch that ‘looks like’ a 50% tone. Next adjust the n-factor on the densitometer until that patch reads 50%.

The n-factor is typically used when a densitometer is used to measure printing plates since printing plates are assumed not to have any optical dot gain.

best, gordo