Digital BW, The Print

"Paul D. DeRocco" <pderocco@i...> wrote:
> 
> What's a color densitometer?

It's a three band narrow band densitometer. It shines a white light, and has three photodiodes with narrow band red, green, and bleu filters. When you measure how much red light is reflected, you now know the "density" of the cyan (red absorbing) ink or dye in a print. Similarly, the amount of green reflected tells you the density of magenta (green absorbing) dye, and the amount of blue reflected tells you the density of yellow (blue absorbing) dye. So it measures (and reports) the densities of the three subtractive primaries: cyan, magenta, and yellow.

They're very useful for checking colors when the colors are produced by cyan, magenta, and yellow dyes or inks, such as a color photograph, a CMKY printing press, or a CMYK printer. The narrowband filters cause substantial color errors whenever the printing process doesn't use CMY dyes. 

> As far as I know, density has nothing to do
> with color. If you buy a colorimeter, it ought to be able to do density as
> well, by arithmetic on the three color values. Can't say for sure what
> software comes with the X-rite, but my spectro will do density, color, and
> spectral measurements.

I don't think X-Rite makes color densitometers anymore. I think the spectrophotometer has pretty much replaced them. As you pointed out, the spectro can do the work of the black and white densitometer (one channel, and a filter that matches the photometric response of the eye, the color densitometer (three narrowband filters designed to "dig into" three dye process color) and the colorimeter (three filters that are designed to match the three color "tristimulus" response of the human eye).

And I have to say, it's nice to run into someone else who signs his messages "Ciao".

Ciao!

Joe