Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: TheLastOfUs on December 26, 2015, 04:38:39 am
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Hey Everyone,
So I'm sort of confused. If the printer...already prints the way it does...and a printer profile simply just takes a differential measurement between what your printer prints and ICC accepted standards of target palette colors...then what is the point of using Photoshop Manages Colors and a Printer Profile?
Does that somehow make colors more accurate, and if so - WHY?
The printer already prints whatever colorspace a certain way..so what on earth can the ICC Printer Profile do differently when coupled with Photoshop Manages Colors to get prints more accurate?
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Hi,
I don't know if the printer driver is colour space aware. So who does conversion from what to what?
Photoshop, or Lightroom gives you the full control of the processing pipe line and the ability to "softproof", that is emulate the printer output on screen and make necessary adjustments.
Best regards
Erik
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Hey Everyone,
So I'm sort of confused. If the printer...already prints the way it does...and a printer profile simply just takes a differential measurement between what your printer prints and ICC accepted standards of target palette colors...then what is the point of using Photoshop Manages Colors and a Printer Profile?
Does that somehow make colors more accurate, and if so - WHY?
The printer already prints whatever colorspace a certain way..so what on earth can the ICC Printer Profile do differently when coupled with Photoshop Manages Colors to get prints more accurate?
In a colour-managed workflow, something somewhere has to convert colours from the image's colour space to the printer's colour space. That's done using the profile of the image colour space, and the profile for the printer/paper combination's colour space.
Generally there are two choices:- The printer driver does it. (The option "printer manages colour" really means "printer driver manages colour")
- The application (e.g. Photoshop) does it.
Either works OK; you just need to make sure one but not both do it.
If you choose 1 then Photoshop just sends the data in the original colour space to the driver. You need to make sure the driver has colour management turned on, and you tell it the colour space of the image (assuming, as Erik says, the driver is colour space aware).
If you choose 2, then you need to tell Photoshop the appropriate profile for the printer/paper combination, and set the driver so that it turns off all colour adjustment. That varies by printer. For example, in Epson printer drivers typically you have to set "ICM" mode, and a sub-mode to "off", or sometimes there's a mode "Off (no color adjustment)".
I find 2 easier, and it's probably better if the image is in a wide colour space such as ProPhoto RGB, as otherwise Photoshop will be sending the image data to the printer as 8-bit ProPhoto RGB, which can result in artefacts on the image.
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so what on earth can the ICC Printer Profile do differently when coupled with Photoshop Manages Colors to get prints more accurate?
Greatly simplified, the printer profile changes the colours sent to the printer to compensate for any errors the printer would make to the colours in the image.
The results from a printer using a good printer profile should be more "accurate", if used correctly.
Note that the word "accurate" isn't a word people like to use here about colour.
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Hey Everyone,
So I'm sort of confused. If the printer...already prints the way it does...and a printer profile simply just takes a differential measurement between what your printer prints and ICC accepted standards of target palette colors...then what is the point of using Photoshop Manages Colors and a Printer Profile?
Well, it's sorta like when a camera captures a raw image and rather than render the image the image like the camera maker's software renders the image with a "look" vs. it renders a different image when using ACR/LR.
Using the Printer Manages Color is pretty much a knee jerk reaction that avoids real color management...a printer has a certain color gamut that is represented by an ICC printer profile–which describes what a printer can print on it's own...using Photoshop Manages Color takes full advantage of what the printer is capable of printing and renders the optimal color management.
Bottom line, you want what the printer company thinks you want or do you want what the printer is capable of printing? I would vote for the complete ICC based capability of a printer. Really, you don't want to use Printer Manages Color if you care for the results you get...
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An output profile is not just for the printer but for printer/paper combination. If you use Printer manages color, you are limited to the few options the printer might have with their own brand of papers.
When you use Photoshop Manages Color, you use the specific profile for the printer/paper combination.
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Bottom line, you want what the printer company thinks you want or do you want what the printer is capable of printing? I would vote for the complete ICC based capability of a printer. Really, you don't want to use Printer Manages Color if you care for the results you get...
Jeff,
I think I may have misunderstood you.
On the various Epson photo printers I've used, the printer driver is capable of ICC colour management. You tell the driver to do use "ICM" (Image Color Management) and you have to tell it the image's profile. It will figure out the printer/paper profile for Epson papers, or you tell it the printer/paper profile. The result is almost indistinguishable from "Photoshop (or Lightroom) manages colors". There are theoretical reasons why the output might differ:
- They're using different colour management engines: an Adobe one for "photoshop manages..." and an Epson (or whatever) one for "printer manages...". The Adobe colour management engines might be better, but in theory at least the printer driver colour management engine could be as good
- The Photshop colour management engine can work on 16 bit data (or probably 15 bit), whereas the printer driver generally gets data already downsampled to 8-bits, so the conversion won't be so accurate.
I find it more convenient to use "Photoshop manages..." (and from point 2 it's likely to be a bit more accurate) but if you're saying that the printer driver isn't capable of ICC colour management, then this isn't my understanding for the Epson printers I've used.
Or have I misunderstood something?
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http://theonlinephotographer.typepad.com/the_online_photographer/2015/07/andrew-rodney-on-the-importance-of-custom-printer-profiles.html
Read what Dave P of Adobe has to state about Printer Manages Color.
Dave Polaschek: First, as to Photoshop vs. Lightroom, if you have set your working space to ProPhoto RGB in Photoshop, and are actually converting documents to that space, Photoshop and LR should produce nearly identical results on the Mac (LR does everything in ProPhoto RGB. Photoshop does not unless you configure it to do so). LR defaults to 16-bit printing on the Mac, whereas Photoshop does not. Otherwise, the code is nearly identical.
On Windows, LR prints using GDI+, while Photoshop prints using GDI. The output between PS and LR will NOT be identical. Both PS & LR use some features of XPS printing to communicate the color management policies to the printer driver, and should behave identically in that regard.
Finally, Photoshop saves print settings with the document, whereas LR saves them in the application preferences.
When I've spoken with Ctein about "Printer Manages Color", I haven't specifically recommended using Epson's color management or ColorSync. I'm pretty sure it just didn't come up. I strongly recommend trying both and using what works better for you.
[Ctein interjects: Colorsync works far worse. It introduces weird artifacts. Epson color is the way to go if you're doing printer-managed color.]
Note that if you are using non-Epson paper in an Epson printer, you can't use "Printer Manages Color" and expect optimal results. But compared to the voodoo most users go through, I still recommend most people use "Printer Manages Color" and pick the closest paper available. It won't be optimal, but it will be good results with a minimum of hassle and no danger of double-color-management or generating a bad profile because the color target was printed incorrectly in the first place, or any of a couple dozen errors people make when attempting to build their own color profiles. This stuff is hard to get right.
Picking "Printer Manages Colors" on Windows guarantees that your color data will be converted to sRGB. We could adopt XPS printing to get around that, but there are many new and exciting bugs waiting to be found by the first application to head down that path.
On Mac, Picking "Vendor Color Management" and "Adobe RGB" does not mean the color data will automatically be converted to Adobe RGB. It means that untagged color data will be treated as Adobe RGB. When I last discussed this with the Apple printing engineers, I got a long explanation of when color conversions will happen, and the printer driver gets a chance to say to the OS "Yes, I can use color data in that color space" or "No, please convert that color data to XXXXX profile for me" (where XXXXX is the default profile for the printer, which you can set in ColorSync Utility.app).
When using "Printer Manages Colors" on Mac OS X, with a printer driver that says "Yes, send the color data as-is" when asked about what the application is offering to print, that data will be passed to the driver without conversion. I've done this with CIELAB data. I don't believe Epson's drivers will accept CIELAB, but when last I investigated (when the x900 printers shipped), they would accept ProPhoto RGB when using "Printer Manages Colors." There was only one conversion of the color data to the printer's final profile, and that was done by the driver.
All else being equal, fewer conversions between color spaces is preferable.
I still think using "Photoshop Manages Colors" is preferable if you take the time to construct an optimal profile, have a challenging document to print, and can manage to do everything correctly. But the results from using "Printer Manages Colors," especially if you are using papers supported by your printer vendor, are extremely close to optimal, and most users should at least give that a try and look at the results before investing in the hardware needed, plus the time needed to build a good color profile.
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Greatly simplified, the printer profile changes the colours sent to the printer to compensate for any errors the printer would make to the colours in the image.
The results from a printer using a good printer profile should be more "accurate", if used correctly.
Note that the word "accurate" isn't a word people like to use here about colour.
Can anyone elaborate more on this? I figured something like this was the case....though not sure why a printer itself Can't correct for its own errors in color?
Maybe I'm missing something here but when I print a print...the printer asks usually if I want it in color...I COULD tell it the type of paper etc....which may change the printers response to something but is that the same as an icc profile when doing printer manages colors? Choosing a paper type in the print dialog box?
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though not sure why a printer itself Can't correct for its own errors in color?
Because it would have know what colours it was actually printing, to do that would it have to measure it's own output.
Not impossible and a couple of high end printers can do that, but VERY, VERY expensive.
which may change the printers response to something but is that the same as an icc profile when doing printer manages colors? Choosing a paper type in the print dialog box?
Yes, printer drivers do change how the printers work depending on paper type being used. It often includes physical changes like how much ink is being sprayed on, how long it's left to dry between passes of the print head even how far the print head is away from the paper surface. All these factors effect the printer's output and the ICC printer profile should be made for one fixed set of paper and settings.
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Surely we need to refer the OP to some more "formal" resources covering colour management?
The Camera to Print and Screen tutorial series available on this site comes to mind.
Andrew should point the OP to his website with its considerable resources.
There is also a good Aussie site that also deals with this stuff: http://www.imagescience.com.au/pages/Colour-Management.html
Tony Jay
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Thanks all. I have read quite a few sites on this subject matter (including the aussie one you linked about a week ago) but naturally a lot of the times I don't see any real site detailing the scientific accuracy of the profiles or really explaining why it helps print more accurately other than just claiming it can help you soft proof or just come up with better colors (with no reason or explanation as to why). Too many sites are just saying the same thing over and over again which is why I decided to seek the forum with my questions.
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really explaining why it helps print more accurately
It's really quite simple and not worth worrying about too much.
When a printer profile is made a spectrophotometer measures the colours the printer actually prints, the profiling software compares them to what colour they should be, then creates the profile to try to make the printer deliver as many colours as it can, as accurately as it can.
Like most things there are good profiles and bad profiles.
You can delve into the deep science that's behind it all, but without the specialised tools and software to explore the whole issue, it's better for most photographer's sanity to just read up the basics* and follow the recommended best practice. Then just get on with taking photographs and making prints and leave the arguments about the theory to the experts.
*Buy 'Color Management for photographers' by Andrew Rodney, pub: Focal Press.
It's the best and easiest read on the subject.
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I just bought Color Management from Camera to Display to Print by Tom Ashe to get a better understanding as well.
One last question - if I have an i1 Pro 2 - it says it does "RGB" printer profiling. Not sure what this means...no printer is purely RGB...did I waste a ton of money ?
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I just bought Color Management from Camera to Display to Print by Tom Ashe to get a better understanding as well.
One last question - if I have an i1 Pro 2 - it says it does "RGB" printer profiling. Not sure what this means...no printer is purely RGB...did I waste a ton of money ?
NO!
Even though your printer uses a CMYK-derived inkset, it is, in fact, an RGB device.
I don't know the book that you quote but if it is any good it should explain the above statement well at some point.
Tony Jay
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One last question - if I have an i1 Pro 2 - it says it does "RGB" printer profiling. Not sure what this means...no printer is purely RGB...did I waste a ton of money ?
It creates RGB output profiles which isn't the same as a so called "RGB Printer". Most GDI and Quickdraw drivers expect to receive RGB data, you build RGB output profiles. The driver then converts to CMYK plus whatever additional inks it might use. So unless you needed to end up with CMYK converted data (for say a printing press), you're fine.
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ICC printer profiles address several different needs.
Pleasing color prints, reproducible color prints, and accurate color prints.
"Pleasing" is what most people want out of their printer. They have an image on screen and want to print it and have it look good. Profiles provide a way to change colors and tone in such a way that the print is both pleasing and reflects what is displayed on screen. ICC profiles call this "Perceptual Intent."
Reproducibility is achieved by using the same profiling software for different paper and printers. Alternately, precision reproducibility of "pleasing prints" where one may use different printers, paper, and or profiles in the future can be achieved using ICC profiles operating in reverse. This is a way to record the colors actually printed when using profiles to create pleasing, but not color accurate, prints. This is typically done by converting the image into printer space using the print profile and selecting "Perceptual intent," followed by converting back to an RGB space using Relative Intent." In the future that image can be printed using Relative Intent and it will be almost identical to the original printed image. There is some loss of precision in the back and forth but it is typically not perceptible even looking at side by side prints.
"Accurate," in the scientific sense is, provided by profiles using either Relative or Absolute Colorimetric Intent. Accuracy is limited mostly by the printer's gamut but also by the smoothness of the printer color to changes in RGB values, the accuracy of the profile's lookup tables, color measurements from which the profile was generated, and drift in the printer over time, temperature, humidity, and operating environment. For instance a printer that has been idle for a few weeks might have significant colors shifts initially.
Relative Colorimetry scales Lab(100,0,0) to the media white points which is often slightly off white. This produces prints, with white borders, that appear the same due to human color adaption to the border "white."
Absolute Colorimetry prints, within the limits of the overall technology, the exact color specified. This is used for proofing and replicating industrial colors. If you are asked to print the color Lab(70,20,20) you would do so using Absolute Colorimetry. It's also very good for reproduction work where you want to exactly duplicate another print or document including keeping the same white point tint as the original documents.
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https://en.wikipedia.org/wiki/Color_management (https://en.wikipedia.org/wiki/Color_management):
Absolute colorimetric
Absolute colorimetry and relative colorimetry actually use the same table but differ in the adjustment for the white point media.
http://forum.luminous-landscape.com/index.php?topic=17323.0
That is not quite right. With Relative Colorimetric (RC), the white point of the RGB working space is shifted to match the media white of the paper (which usually isn't neutral). All other colors (including the gray axis) are shifted accordingly. This is exactly what "media relative" means. With Absolute Colorimetric (AC) the white point of the RGB working space isn't shifted; consequently highlight detail will/may be somewhat clipped because the white point of the RGB space (e.g., LAB = (100,0,0)) usually can't be reproduced on the paper. So the neutral highlights with AC will be a little dimmer (darker gray) and you might lose some detail.
Since colors are shifted with RC due to the white point remapping, the definition of gamut boundaries can also change. Thus, what is out of gamut with RC may not be the same as what is out of gamut with AC.
Again, as Andrew says, the practical advice boils down to trying the various intents and picking the one that works best for your image, on an image-by-image basis. Profiles know nothing about the image content, so that's where you have do make the judgment.
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One last question - if I have an i1 Pro 2 - it says it does "RGB" printer profiling. Not sure what this means...no printer is purely RGB...did I waste a ton of money ?
The i1Pro2 is an excellent high end bit of kit, but really is likely to be a waste of money if you don't understand what it does and why you might find it advantageous.
It's the sort of luxury you might consider when you FULLY understand colour management and can implement it correctly.
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The i1Pro2 is an excellent high end bit of kit, but really is likely to be a waste of money if you don't understand what it does and why you might find it advantageous.
It's the sort of luxury you might consider when you FULLY understand colour management and can implement it correctly.
Well sure I don't understand everything it does. Not completely clueless so I think we can hardly say it's a waste of money. I don't believe in the concept of FULLY knowing everything in order to start using it. I believe we can still learn from things beyond us and use it while slowly understanding its technical aspects. That's like saying one cannot walk without fully understanding how to walk. It kind of just develops through trial and error like anything else I'd expect.
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Well sure I don't understand everything it does. Not completely clueless so I think we can hardly say it's a waste of money. I don't believe in the concept of FULLY knowing everything to start using it and learning from it while slowly understanding its technical aspects. That's like saying one cannot walk without fully understanding how to walk. It kind of just develops through trial and error like anything else I'd expect.
It's a very good tool and there is nothing better to increase understanding of color printing than a tool that you can use to check your process. It's like reading about how a mill or lathe works. Nothing like actually having them when reading about how to use them.
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Hey Everyone,
So I'm sort of confused. If the printer...already prints the way it does...and a printer profile simply just takes a differential measurement between what your printer prints and ICC accepted standards of target palette colors...then what is the point of using Photoshop Manages Colors and a Printer Profile?
Does that somehow make colors more accurate, and if so - WHY?
The printer already prints whatever colorspace a certain way..so what on earth can the ICC Printer Profile do differently when coupled with Photoshop Manages Colors to get prints more accurate?
If you like the results from printer managed color, then do not bother wth a color managed workflow. I am sure if you make enough prints of an image, you will figure out how to make the result look attractive.
Bob
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It's really quite simple and not worth worrying about too much.
When a printer profile is made a spectrophotometer measures the colours the printer actually prints, the profiling software compares them to what colour they should be, then creates the profile to try to make the printer deliver as many colours as it can, as accurately as it can.
Unfortunately this is really not how it works.
I'm all for simplification and analogies but if they create an idea in people's minds that is incorrect then I don't think they're a good idea.
In 2003 I wrote an entry (http://www.colorwiki.com/wiki/Color_Management_Myths_1-5#Myth_.232:_There_is_some_internal_Lab.2FColor_reference_that_the_output_of_printers_is_compared_to_when_profiling) in our "Color Myths" series about this very topic.
The process of building a printer profile samples the colors produced when device values (RGB, CMYK, whatever) are sent to a printer and measured. Then, in the future, when a color value (Lab) is desired on the printer, the printer profile outputs the device value that will produce that color (or something close that agrees with other colors in the process).
It may sound like splitting hairs but I assure you, it's different. And for those who choose to study the process further, they won't come to a confusing point and have to unlearn their initial ideas behind the process.
To return to the OP's post:
If the printer...already prints the way it does...and a printer profile simply just takes a differential measurement between what your printer prints and ICC accepted standards of target palette colors...then what is the point of using Photoshop Manages Colors and a Printer Profile?
Does that somehow make colors more accurate, and if so - WHY?
So, as I mentioned above, the printer profile is not about a differential measurement. It's about rendering the color you want in the best way possible.
If you let the driver perform the conversion then it uses its own internal profile. If you are happy with the output of the printer in it's default behavior, then you're good. But be assured, a profile is being used in either case.
But if you find your shadows are plugged, your highlights are blown out, your reds are tomato, your blues are purple or any of a large number of color rendering problems, then a custom profile could very well do a better job getting you the color you want. And letting Photoshop perform the conversion is more likely to get the results you want.
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It may sound like splitting hairs
It is ABSOLUTELY splitting hairs.
Bringing things like 'LAB values' into trying to explain how the absolute basics of custom printer profiling works to someone without any idea is not at all helpful.
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It is ABSOLUTELY splitting hairs.
Bringing things like 'LAB values' into trying to explain how the absolute basics of custom printer profiling works to someone without any idea is not at all helpful.
Ok, remove that word from my description. Then I think it stands pretty well as a lay-person description of the process.
Also I'd prefer to leave it to the OP to decide if it's useful.
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If you like the results from printer managed color, then do not bother wth a color managed workflow. I am sure if you make enough prints of an image, you will figure out how to make the result look attractive.
Bob
With the Epson printers I've used (R2000, R1800) you can have colour-manage workflows with either the program or the printer (driver) implementing colour management, provided you enable that function in the printer driver. The results are near-identical.
I use colour management in the program (Photoshop or Lightroom) as it's more convenient, but both work.
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In theory, to obtain a color managed workflow, we would like each device to calibrate/profile itself. So the monitor should do whatever is necessary to display RGB values from a file with absolutely accurate color, and the printer should do whatever is necessary to print RGB values from a file with absolutely accurate color. Of course absolute accuracy is not always possible, since gamuts do not completely overlap, but that is the ideal. An application like Photoshop is then responsible only for producing files with correct RGB values in a properly tagged color space.
The same result can be obtained by letting an external application change the RGB values that it sends to the printer, while telling the printer it is no longer responsible for color management. For this to work, the external application must know the characteristics of the printer. This breaks the paradigm of device-independence and seems rather backward. Why should Lightroom know how your Epson printer renders RGB values into ink colors better than the printer itself? Nevertheless, this has historically been the case, and most of us have gotten used to working this way, because it gave better and more reliable results. If printers are finally becoming capable of handling their own color management, it would be good to be able to go back to that model.
Maybe a contrived example would help. Suppose your printer prints RGB=(128,128,128) with a blue tinge when color management is turned off. (Assume the color space defines this color to be neutral gray.) You create a printer profile to compensate for this. The profile says something to the effect that in order to print (128,128,128) accurately, the printer must be told to print (128,128,112). That profile can be loaded into the printer, with color management turned on, so that when it receives (128,128,128) it attempts to print (128,128,112), which comes out as neutral gray. Or the profile can be applied by the application, so that it translates (128,128,128) into (128,128,112) before sending the image to the printer, with color management turned off. The end result should of course be the same.
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It is ABSOLUTELY splitting hairs.
Bringing things like 'LAB values' into trying to explain how the absolute basics of custom printer profiling works to someone without any idea is not at all helpful.
Introducing the concept of a Device Independent intermediate colorspace is essential for curing the common misconception shown by the OP that color profiling is about "correcting the devices color".
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In theory, to obtain a color managed workflow, we would like each device to calibrate/profile itself. So the monitor should do whatever is necessary to display RGB values from a file with absolutely accurate color, and the printer should do whatever is necessary to print RGB values from a file with absolutely accurate color.
ICC style color management doesn't work like this, because it isn't that narrow or fixed in function.
You are assuming some sort of definition of how an RGB value "should" be displayed or printed. No such thing exists in relation to a single (general purpose) input or output device. They behave how they behave - profiling captures that and deals with making them do something useful at a higher (system) level. Rather than repeat myself, you should read this (http://www.argyllcms.com/doc/ColorManagement.html).
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Of course we must consider the non-uniform nature of Lab space as a intermediate color describer which happens to have a history of issues with blues turning purple. So nothing's perfect in this coding color box. Just FYI. Not arguing the matter.
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Of course we must consider the non-uniform nature of Lab space as a intermediate color describer which happens to have a history of issues with blues turning purple.
Now that really is a quibble - any slight non-uniformity in L*a*b* is insignificant compared to it's huge increase in perceptual uniformity compared to XYZ, and of absolutely no consequence as a space to represent color value in, where it has the property of great efficiency. It only has any consequence if used as a gamut mapping or clipping space.
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And remember, in Ps, at the user end at least, Lab values are integer. which is not a good thing.
Brian A
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And remember, in Ps, at the user end at least, Lab values are integer. which is not a good thing.
L*a*b* values (like all other colorspace values) are whatever precision you choose them to be. In 8 bit the a* & b* are integer and the L* has 1 binary bit. If you choose 16 bit, they are not integer.
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So are all ICC profile transforms calculated with 16 bit precision?
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So are all ICC profile transforms calculated with 16 bit precision?
As a practical matter, yes. ICC profiles do allow 8 bit LUTs for printers but I've never run across one. Standard profiles are calculated using 16 bits but the larger source of error is the LUT interpolation.
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I tried to tell the nut case who runs Photography Life that. No use.
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So are all ICC profile transforms calculated with 16 bit precision?
The precision used by the profile has nothing directly to do with the precision used in transforms, although it does limit the overall precision of course.
For instance, ArgyllCMS's icclib has always used floating point for transforms, and so has lcms from V2.
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Unfortunately this is really not how it works.
I'm all for simplification and analogies but if they create an idea in people's minds that is incorrect then I don't think they're a good idea.
In 2003 I wrote an entry (http://www.colorwiki.com/wiki/Color_Management_Myths_1-5#Myth_.232:_There_is_some_internal_Lab.2FColor_reference_that_the_output_of_printers_is_compared_to_when_profiling) in our "Color Myths" series about this very topic.
The process of building a printer profile samples the colors produced when device values (RGB, CMYK, whatever) are sent to a printer and measured. Then, in the future, when a color value (Lab) is desired on the printer, the printer profile outputs the device value that will produce that color (or something close that agrees with other colors in the process).
It may sound like splitting hairs but I assure you, it's different. And for those who choose to study the process further, they won't come to a confusing point and have to unlearn their initial ideas behind the process.
To return to the OP's post:
So, as I mentioned above, the printer profile is not about a differential measurement. It's about rendering the color you want in the best way possible.
If you let the driver perform the conversion then it uses its own internal profile. If you are happy with the output of the printer in it's default behavior, then you're good. But be assured, a profile is being used in either case.
But if you find your shadows are plugged, your highlights are blown out, your reds are tomato, your blues are purple or any of a large number of color rendering problems, then a custom profile could very well do a better job getting you the color you want. And letting Photoshop perform the conversion is more likely to get the results you want.
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 ! ;)
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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 ! ;)
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.
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So, for the sake clarity and the removal of doubt, do I understand correctly that you are saying ....
See What's the difference between Calibration and Characterization ? (http://www.argyllcms.com/doc/calvschar.html)
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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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See What's the difference between Calibration and Characterization ? (http://www.argyllcms.com/doc/calvschar.html)
Got that too.
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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...
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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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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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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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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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