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Author Topic: Photoshop Manages Color - Pointless?  (Read 17277 times)

Simon J.A. Simpson

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Re: Photoshop Manages Color - Pointless?
« Reply #40 on: January 11, 2016, 04:55:53 am »

Calibration doesn't normally apply to printers.  Printers are profiled, which means measuring the colour space of the printer (usually the printer/paper combination).   

Calibration normally applies more to monitors, where calibration and profiling are two processes, normally done at the same time by the software that comes with the colorimeter or photometer.  Here's what happens with monitors:
  • The software calibrates (adjusts) the monitor to a known white point and tone response curve (TRC, or gamma).  This will be with a combination of hardware adjustments to the monitor and a Look Up Table (LUT) that's loaded into the driver, and is used by the driver to adjust the TRC and white point.  Normally the colour space is fixed, but some wide-gamut monitors can emulate a narrower gamut, and for those monitors the colour space itself can be calibrated (e.g. to sRGB).
  • After calibration, the monitor is profiled (measured): the colour space and calibrated TRC and white point are measured, and that measurement is put in the profile. (The LUT created by calibration is normally also saved in the profile, but it isn't technically profile information.)
Printers are just profiled, they are not normally calibrated first. 

Colour-managed programs, when they output to a monitor or printer, take the profile and map colours from the image colour space (sRGB, Adobe RGB or whatever) into the monitor's or printer's colour space, as defined in the profile.

Yuh, got that.
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Steve Upton

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Re: Photoshop Manages Color - Pointless?
« Reply #42 on: January 11, 2016, 03:39:47 pm »


So, for the sake clarity and the removal of doubt, do I understand correctly that you are saying the you are using the word “calibrate” to mean ‘measure and adjust to an external standard’ (e.g. colour temperature) whereas (and put simply) you are saying that a device profile (e.g. that of a printer) describes the behaviour of the device which allows colour management software (e.g. ‘Adobe ACE’ colour engine) to produce as accurate appearing as possible a range and relationships between colours that the device can produce/encode; and (for the sake of completeness) in order to facilitate this there are, in addition, a number of ways of interpreting this “accuracy” which are the Rendering Intents (e.g. “Perceptual”, “Absolute”, etc..) ?

Without getting too technical have I, in essence, understood correctly ?  I am happy to be corrected where I may have got it wrong but colour management pedants please desist from being picky !   ;)

Basically, yes. You have it.

I like how your explanation waffles a bit on accuracy as accuracy is a) very tough to define, b) tough to achieve, and c) often not strictly desired. It's why I said "or something close that agrees with other colors in the process" as the "agreement" with other colors (including the paper) is how rendering intents get involved.

now from a different Simon...
Quote
Calibration doesn't normally apply to printers.  Printers are profiled, which means measuring the colour space of the printer (usually the printer/paper combination).   

I'd prefer to flip this around and say that when printing to an inkjet using manufacture drivers, calibration doesn't apply. In ALL other types of printing: RIP-driven inkjet, offset, flexo, screen, gravure, etc, etc, etc, calibration most certainly does apply (and is very important)
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Simon Garrett

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Re: Photoshop Manages Color - Pointless?
« Reply #43 on: January 11, 2016, 06:59:17 pm »


now from a different Simon...
I'd prefer to flip this around and say that when printing to an inkjet using manufacture drivers, calibration doesn't apply. In ALL other types of printing: RIP-driven inkjet, offset, flexo, screen, gravure, etc, etc, etc, calibration most certainly does apply (and is very important)

Point taken!  As you say, I was talking about consumer printers using manufacturer-supplied drivers. 
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Simon J.A. Simpson

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Re: Photoshop Manages Color - Pointless?
« Reply #44 on: January 12, 2016, 11:25:09 am »

Basically, yes. You have it.

I like how your explanation waffles a bit on accuracy as accuracy is a) very tough to define, b) tough to achieve, and c) often not strictly desired. It's why I said "or something close that agrees with other colors in the process" as the "agreement" with other colors (including the paper) is how rendering intents get involved.


Thank you, Steve.  Yes I did waffle around a bit with “accuracy”.  Actually, I struggled with it – and did injury to the English language as a result.  Apologies all round  :-\
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Doug Gray

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Re: Photoshop Manages Color - Pointless?
« Reply #45 on: January 12, 2016, 03:11:17 pm »

Thank you, Steve.  Yes I did waffle around a bit with “accuracy”.  Actually, I struggled with it – and did injury to the English language as a result.  Apologies all round  :-\
Much of this is because of the erratic history of ICC color profiles. Especially the ways manufacturers implemented them. It has settled down and is now a mix. Perceptual Intent and Saturation Intent specifically allow printer manufacturers to tailor output color mapping pretty much without limitation. Relative Intent and Absolute Intent are now measurement based for colors within gamut and some of the older variations such as implementing BPC have been eliminated. Still, for those colors outside the printer's gamut mapping is not specified but is supposed to be unsurprising. For instance mapping these colors to the nearest gamut boundary.
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Ernst Dinkla

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Re: Photoshop Manages Color - Pointless?
« Reply #46 on: January 15, 2016, 04:45:44 am »

Point taken!  As you say, I was talking about consumer printers using manufacturer-supplied drivers.

There are wide format printers with manufacturer supplied drivers, for Windows + OS-X, that have ether spectrometers aboard for both calibration + profile creation; HP Zs standard, Canon iPF+ Epson optional, or have standard a densitometer aboard for just calibration; Canon iPF. The last solution could also be found on some older consumer desktop models like the HP B9180.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots
« Last Edit: January 15, 2016, 04:49:49 am by Ernst Dinkla »
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