CHROMiX

LCH Values

I have recently been creating Linearisation files for a variety of inkjet printers, I have been reading on these forums about measuring to the max Chroma. This seems a good idea to me, but how do you find the max Chroma and are there any standard values?

Sorry for such a stupid question, but I’m new to this, and anything that I can do to get better results I’m interested in finding out how.

Chroma is just the measurement of the color of a colored ink.

I will use Cyan as an example. Just because it is a Cyan ink head it does not mean this ink head always prints pure cyan - density build-up can change the color into something else which reveals a limitation of using density as a guide to setting ink limits / ink restrictions.

Print a raw grad of cyan from 0 to 100% with no profile or ink limit getting in the way. Most profiling & RIP software lets you do this - you can’t do it just with an application and a printer as the ink limits are canned and always applied by default.

Take a spectrophotmeter like an Eye 1 or an Xrite Pulse and some software that can read & display Chroma values.

Read the patches and you will get a reading of the Cyans “chroma”

You will find that usually the Cyans Chroma increases along the strip in a linear fashion but nearer the top end you get a shift towards blue - ie you have gone past the point where Cyan is maximised - where you should place your ink limit - and are now into Hue shift - not good!

Most software lets you visualise this as a curve - it increases to a high point (max Cyan in this case) before curving away into another color (blue in this case) Call your ink limit at the top of this curve.

Thus your ink limit is placed at the best point possible - where Cyan is maximised. Using only density as a guide you often push onward into blue and this can give your profile a headache and waste ink.

Magenta suffers in the same regard but yellow tends to stay yellow and you can use density as a guide here. Black is obviously a density reading, rather than Chroma!

Change your paper, printer or ink set and these values are meaningless - thus there can never be a “correct” chroma value

AJ

Thanks for the reply, what software would you recommend for reading Chroma Values, I have the i1.

If you have an eye one, just download ProfileMaker from the xrite website and only install MeasureTool. It will run without the hardware key. Change the default reading from Lab to LCh.

The chroma value itself won’t tell you what the color shift is, it will only show you the purity of the color. Start at the 100% patch and move down looking for the highest chroma value (middle number in LCh) the h or Hue value will show you what the color is, or a shift in color from say cyan to blue.

Hope that helps.