CHROMiX

Can I get curves in form of density

Hello, trying to understand can I get curve3 curves in form of density?
I would like to linearize a small format rip

The linearization should I say ink limiting is set like this after measuring straight curve printout for every channel.

The minimum max ink is set separately, and should not be changed:

1.I thought I could use curve3 to enter the measured values and that should make grayscale neutral right?

  1. What about light channels, curve 3 provides curves only for CMYK channels?

  2. How to get curves in form of density values ?

Curve3 is designed to accept measurements of a P2P target print using a spectrophotometer. This measurement will return spectral or Lab values that are accepted by the Curve3 software. The software then calculates the ideal 4-color curves in the form of CMYK percentage values that can be exported to a RIP. These percentage values can then be applied to the calibration tables of most RIPs.

It sounds like you have a RIP that wants to see density values instead of % CMYK values. Curve3 will not do that.

Most RIPs will take care of the handling of light magenta & light cyan automatically with the rest of the CMYK. If you DID have a RIP that worked with true 6 channel color, Curve3 has a new feature that provides a way to calibrate those 2 “special inks”.

Isn’t exporting to Konica Minolta XML preset exports densities?

No, the KonicaMinolta export just provides a lists of control points in a scale of 0 to 255 to create a curve for each of the four colors. These are not density numbers, but rather values the printer uses to determine color. So like most of the Curve exports, these are “device” values.

So why no density exporting then???

You can make Photoshop curves, even device-link profiles, but no density?
Any converters aout there that would perhaps make density curves from device link profile?

I guess the answer goes back to what G7 is. The whole idea of G7 is that in this modern age people in the pressroom can take advantage of these new, modern measurement instruments that can capture color the way our eyes do. These inexpensive spectrophotometers like the i1Pro capture the whole spectrum of visible light. That makes it possible to linearize a press to a neutral curve and thereby make it more likely for all the other colors to fall into line, have other presses match it much better, etc. In G7 and in Curve3, we’re calibrating a press so that the gray tones visually look gray as measured by the instrument. But it all depends on being able to measure color. A densitometer does not actually measure color - but rather different shades of gray. You put different filters in front of it in order to get it to return a density for the different colors, but it is still a densitometer - it measures density not color. And it requires an instrument that deals in colorimetry to measure actual color.

Comparing density to colorimetry in this case is sort of apples to oranges.
G7 is a newer method and requires these newer instruments in order to work.

Yes I know curve3 and G7 needs a spectrophotometer to work. These are even cheaper than densitometers these days.

I think curve 3 gives output in lab? This could be converted to density?

I wonder how can curve3 use so many times less patches than say i1upgrades has some optimization gray chart that uses like 2500 patches but the result is very bad on non linear printers (printer that use driver RGB pinters)

Could curve 3 be used to linearize RGB printer if used with device link generated profile in color server workflow?

Curve3 does not give output in Lab. The output is in device values - the number format that the RIP or printer requires in order to adjust color. Most RIPs are looking for CMYK ramps that run from 0 - 100 % These are like the printer color control numbers. Again, this has nothing to do with density.

Curve3 is fundamentally a linearization procedure, not a profiling method. It sounds like the i1Profiler gray chart you were talking about is part of optimizing a profile? That would be something different.

Yes! Curve3 can be used for RGB systems by using either the device link profile or the Photoshop curve output option. That’s pretty much what those options are there for. DL would be more precise. You can use this to apply the G7 curving to an image in Photoshop, and then print normally - and the image will be correctly “curved” according to the G7 method, without having to actually go through a RIP.

Don Hutcheson talks about this option at the 51 minute mark of this YouTube video:
youtube.com/watch?v=wLC9mBbwmy4#t=51m55s

Thank you for reply. Where can I download reference file for P2P25xa G7 Calibration Target ? I need LAB reference to use it in a comparison software other than curve3.

Any of the G7 P2P targets and references can be downloaded from Don Hutcheson’s site here:
hutchcolor.com/Images_and_targets.html

These reference files will contain the CMYK device values only. If you need Lab values, you would need to measure the targets - or simulate a measurement by applying a profile to the reference values in a program like ColorThink Pro. Let me know if you need help with that.

Yes please provide instructions on how to convert to LAB. Thank you.

Here’s a procedure for doing this in ColorThink Pro:
colorwiki.com/wiki/Simulating_printing