CA2327749A1 - Product for ensuring consistent accuracy in color printing and method of its use - Google Patents

Abstract

The invention is a combination of print medium bundled with took-up tables that provide custom Destination Characterization Profiles specific to the medium and printing device. The profiles are typically constructed by the medium manufacturer who has access to data on manufacturing variables that can affect color reproduction. An extensive sample of the media is taken and evaluated for color printing accuracy on a given device. Average values of media performance are built into the custom profile so that there is no necessity for the ultimate user to create profiles on site.
Custom profiles are constructed for each device that will use the medium and for each grade of medium.

Description

23,440 PRODUCT FOR ENSURING CONSISTENT ACCURACY IN COLOR
PRINTING AND METHOD OF ITS USE
S The present invention is directed to a method of eruuring consistent and accurate color reproduction with printing devices using different priniizig media or with different devices using a given medium. The invention is further directed to the com-bination of printing media bundled with look-up tables that provide profiles specific to a given printing device using a given medium Background of the Invention In recent years printing devices using a digital input have become of great importance in reproduction of documents. These devices include, but are not limited to, xerographic, inkjet, dye sublimation, thermal transfer, and wax transfer l5 types. Included as well are other conventional printing devices such as o~'set presses that racy also obtain their inputs in digital form; e.g., the digital files used in the prepa-ration of printing plates. Accurate color reproduction is subject to many factors which introduce color variation between the object imaged and its appearance on a printed page. There is significant variation in the color image recorded between imaging dc-ZO vices of different types and even variation between presumably identical models of the same type madc by a given manufacturer. Image recording devices are as yet unable to capture colors in the same way that it is perceived by the human eye.
Scanners or digital cameras are common color image rapture devices although computer generated images; e.g., eornputer art, are also very important. The 25 digital image capture device will create an image by encoding intensity levels of red, green and blue (RGB) for each individual pixel recorded. These color channels are typically represented by 8 bit encoding each having 2S6 intensity levels. If printed without modification the resulting file would form a color image noticeably different from that of the object imaged. In other words, it would reflect the inherent and un-30 avoidable bias of the image capture device. Manufacturers have long been aware of the inherent bias in their devices and normally include irnernaI software (or firmware) to compensate for it. This software is in the form of so-called "look-ap tables".
These are initially developed empirically or mathematically using standard colortmetry and appli-cation of color reference standards. The look-up tables enable a Color Management Module (software application) to accurately map the red, green and blue (RGB) values ofeach pi.~tel in the source image so that when it is then rendered on a monitor or other destination device, the image mute closely resembles the object originally imaged_ Commercially available Color Management Profiling software or proprietary software can used. for creating or modifying look-up tables_ This software, developed for a nar-row specialty market, is complex and expetuive and requires considerable time, e$'ort, and skill for its e$ective use.
The problem of acourate color rendition dots not stop with the digital image source. Biases also exist in the image reproduction device; e.g., a printer or 1 U monitor, so that without additional correction the color values of an input image file would be output somewhat differently on the display or printed medium. This bias ex-ists between different printer models and types and even between apparently identical printers. Normal variations between different ink or pigment batches can create further coloc error. In similar fashion to that used with the imaging devices, look-up tables are used with image reproduction devices to compensate for internally introduced color error as much as possible. Here also, Color Managetneni Profiling software can be em-ployed to effect color modification by altering existing look-up tables or creating new ones.
Even as modified by a look-up table, the output of an image capture de-vice cannot normally be used directly as the input to an image reproduction device. It is as if they speak mutually unintelligible languages and require a translator. This is because the image encoding, e.g., in RGB values, is generally local to the device.
Stated otherwise, the encoded color information is device dependent. This necessary translation is accomplished by mapping the RGB values of the image capture device, as given by its look-up table, into some form of absolute rnlor description. This absolute color description is often referred to as the Profile Connection Space. Most typically this Profile Connection Space is the L*a*b* color system. L~a'b* coordinates (also called CIELAB) are a device independent color difference space established by the Commission lnterrrationale d' Eclairage that quantifies object color under standard 3U viewing and illuminant conditions. The h* axis represents white/black values, the a' axis is the redlgreen value, and the b* axis is the yellow/blue value. An L*a*b* triple represents a fixed point in three-dimensional color space.
The source image look»up table (or Source Characterization Profile) consists of its R,G,B, triple and associated Lia*b* coordinates. In a color managed International Color Consortium (ICC) compatible workflow the L*a*b*
coordinates are attached or embedded into the RGB image tile to form a tagged source image file that can be output as a TIFF, JPEG, or similar data format. Once a source image file is "tagged" with its Source Characterization Profile, embedding allows the file to be ex-changed or rendered on a different device since the source image file now carries de-vice independent color information.
Downstream, the tagged image file (along with its Source Characterize-tion Profile) carrying L*a*b' values for each pixel, is loaded into a computer. In prac-tice, software called a Color Management Module relies on the Profile Connection Space as a common link to connect the Source Characterization Profile of the scanner, monitor, or camera to the Destination Characterization Profile of the monitor or printer.
'This complex chaining of source to destination profiles is the mechanism that enables accurate, device specific, color signals to be sent to the printer. As was noted earlier, the reproduction device may use xerography, ink jet technology, or other conventional marking technology to produce an image on a given medium. More specifically, the Color Management Module software initially maps the RiG,B, source values of the im-age into the Profile Connection Space L*a*b*. It then,, for each pixel, maps the L*a*b*
values into either RZG2Ba or CMYK (cyan, magenta, yellow, black) values using the printer's Destination Characterization Ptoflle, depending on the nature of the printer driver. To keep the size of profiles small. look-up tables are sparsely sampled and re sponsibility falls to the Color Management Module to use interpolation to overcome the coarse quantization. This remapping from R,GiBi to L~a*b* back to RzGZ$= (or CMYK) accurately directs the deposition of appropriate amounts of cyan, magenta, yellow, and black colorants onto the medium for each pixel in the input or source image file.
It should be apparent that to ensure accurate color reproduction across devices each individual make or model of image capture device and reproduction de-vice will require custom derived source and destination look-up tables (proRles) re-spectively.
There is one more very significant source of error in rendition of the ul-timate printed image. That is the nature of the media itself Considering paper as the most typical printing media, the many types and brands available each have different chemical, physical, and optical properties that affect a printers Color reproduction. Im-age degradation or demodulation can occur in many ways. Some typical interactions that affect color rendition are diffusion of light by the substrate, adverse chemical reac-dons of colorant or pigment with the usual additives of the paper, show through from excessive wetting, loss of sharpness from colorant spreading, and loss of density from colorant absorption or irLSUt~cient colorant transfer. A given color of red may be used S as an example. Using a given printer with the same input data file, the red would ap-pear different to a viewer if printed on plain xerographic, laser, coated inkjet, or photo glossy grade papers, to name but a few types. Similar differences would also be noted using the same grades of paper supplied by different vendors on the same printer. The color would further appear different using a given paper and the same input data file with different printers using the same marking technology or with printers using differ-ent marking technologies.
This effect of the reproduction.medium on color rendition is well recog-nized by printer nnanufacturers. Manufacturers of more sophisticated printers provide several individual look-up tables, each developed to represent different generic grades 1 S of paper. However, these tables are usually created from a very limited sampling of the particular medium type. In practice such profiles do not adequately represent the vari-ability found with commercial papers belonging to a given grade class. The generic grade profile does not capture media variability such as fiber type arid pigment content, sheet topography, optical differences, type and concentration of internal and surface sizing, surface treatment, and the unique chemical and electrical properties of that grade. Generic profiles have not been able to take into account the manufacturing variation within a given media type or grade from an individual rnanufacturez or be-tween the same grades of rnedia made by different manufacturers. The assumption that like fades from different manufacturers are homogeneous rarely holds true. To etzsure 2S accurate color reproduction the Destination Characterization Profile should be modified every time there is a change of medium. Stated otherwise, for a given output device and marking method, its optimum Destination Characterization Profile is media de-pendent. Sometimes the profile must even be modified between different orders from a given paper supplier due to manufacturing variability. At best this represents a consid-erable nuisance factor. At its worst, if not done with care and precision, it can result in costly rejection of a job order by the customer because accurate color reproduction has not been precisely achieved.
The present invention is directly suitable for any type of printing device receiving a digital signal and indirectly suitable for conventional presses relying on digital image plate setting technology. The invention deals with media specific output characterization products and methods. It assumes that input and output imaging de-vices used in a given workflow can be calibrated; i.e., set to operate in a known state of physical condition. The further assumption is nnade that the color reproduction device has been linesrized or that its behavior is essentially linear.
Summary of the Invention The present invention offers a solution to the problem of media varia-tion in color hard copy reproduction. It is a vendor supplied product and method en-sating accuracy of color. reproduction for each speciFe type of printing medium. The media specific profiles of the invention effectively reduce or eliminate the need far look-up table development and/or modifications that must be performed by the user of the media. While the medium most frequently used will be paper, the terms '=medium"
or "media" should be read more broadly to include paper-like substrates comprising synthetic polymers and/or fillers or other materials that can be handled in a similar fashion to paper.
Throughout most of the paper industry, manufacturing tolerances for paper grades are closely held within commercially practical limits. However, them is still some unavoidable variation between different production lots. The method of the present invention first requires determining the range of variability in color reproduc-tion or printing properties for each specific print medium. By "specific print, medium"
is meant a given product grade from a given manufacturer. It may be necessary to treat nominally identical products made by a particular manui-acturer at different production times or in dif~'erent mills as different specific print media. Average values of color rendition of the media will be determined on printed images by multiple measurements using statistically valid sampling techniques. The term "average values"
should be read sut~iciently broad to include either arithmetic mean, geometric mean, or median values.
This measurement will determine the maximum variation in color reproduction which might occur between different production lots of the medium or within any given lot_ Variation is defined here as deviation from expected color. Manufacturers strive to keep this variation quite small. However, manufacturing realities are such that some degree of variability is always present. Color measurements are usually made using a colorimeter or spectrophotometer. These are compared with the expected values de-fined by the target L'a'b* coordinates using standard Color reference samples-At least one look-up table will then be constructed for each specific print medium using the av-erage values of color rendering parameters averaged over each type of medium and im-age reproduction or printing device. The preferred statistic indicating central tendency is the median. The term "look-up table" refers to device characterization profiles for both input and output devices. Given types of image reproduction devices are those which are nominally identical to each other and which use pigment or ink supplies which are nominally identical from lot to lot.
In essence, media specific profiles are constructed for optimizing the hard copy imaging system The resulting look-up table or tables will most preferably be supplied or made available with the medium by the medium vendor. They can be supplied in a number of known ways of digital data transmission; e.g., by floppy disks, CD-ROM compact disks, digital phone transmission, spanner or visually read labels, embedded in computer operating systems, embedded in printer drivers, embedded in raster image processors, or by downloading from the Internet. A UPC bar code label 1 S supplied with the shipment can provide a code or key used to identify an appropriate look-up table. The supplier can have an TP/LJRL address on the World Wide Web where the customer can readily download look-up table data relative to the supplier's specific media products. The latter method has a particular advantage to the imaging community that uses a number of different image reproduction devices and different types of paper. They can enter a medium shipment number or other media identifica-cion code and specify the particular device or devices to be used with the medium Any of these methods enables the look-up table data to be readily assigned as a medium specific Destination Characterization Profile for the specific printer to be used.
It is thus an object of the invention to provide a product comprising in combination a custom derived look-up table bundled with a specific lot of print me-dium.
It is also an object to provide printing media so that consistent and accu-rate color reproduction can be readily achieved on a given printing device using the media without the need for the user to derive look-up tables specific to the media 3U It is a fiuther object to provide a product with multiple custom derived look-up tables for a particular grade of print trsedium to readily accommodate use of the medium with printers having different color rendering characteristics.
It is another object to provide a unique method of ensuring corLSistent and accurate color reproduction that compensates for medium and device variability.

It is yet a further object to eliminate the need for the imaging community to create or modify look-up tables for every new shipment of print medium.
It is still another object to provide a unique method for overcoming me-dia limitations in color reproduction due to possible adverse media-colorant interac-S tions.
These and many other objects will become readily apparent upon read-ing the following detailed description taken in conjunction with the drawings.
Brief Description of the Drawings FIG. I is a flow chart showing the usual progression of data through an image capture device creating an outflow of input data to a printer.
FIGS. 2 and 3 are illustrative of look-up rabies describing respectively Source ChatacteriTation Protiles and Destination Characterization Profiles to make the input of an image capture device compatible with the output of an image reproduction device.
FIG. 4 is a flow chart showing the progression of input data to a printer or other image reproduction device_ FIG. S is illustrative showing how customized look-up tables can be used to optimize print quality of a particular printer using a given medium.
FIGS. 6A and 6B are illustrative of the method of derivation of media specific custom Destination Characterization Profiles.
Detailed Description of the Preferred Embodiments The present invention will be more readily understood by reference now to the drawings. FIGS. 1-4 represent the present state-of the-art color imaging system processing input data into a form suitable for a data supply to a printer. As seen is FIG.
1, a digital representation of the object, drawing, painting, etc_ to be reproduced is cap-tured by a device such as a digital camera or scanner. The digital representation tray also be created as original art or illustrations on a computer using various forms of graphics,software. The image capture device output is a raw digital file in which each pixel is assigned a numerical value for the red, green, and blue composite channels of the object represented by that pixel. The particular image capture device or method used is known to have inherent color representation limitations that introduce biases or inaccuracies into the raw RGB image data file. When it is desired to render this image on another device such as a monitor or printer it is necessary to compensate or correct for these inherent biases. The raw RGB pixel data are used to enter a look-up table where appropriate corrections, unique to the particular image capture device, are made in the initial RGB data, FIG. 2 is illustrative of a hypothetical look-up table for an eight bit data capturing system. The R,G,B, values are associated with their CIE
L'~a*b* coordinates to form a Source Characterization Profile. Commercially available Color Mana,g~ment Profiling software may be used to assign appropriate L*a*b*
values to the R,G,B, values based on measurement ofcolor reference standards.
The look-up table may be one supplied by the manufacturer of the image capture device as internal firmware or software. Alternatively, it may be ~rea~ed or modified by the use of any of the various Color Management Profiling software pro grams. To ensure greatest accuracy of color reproduction, the imaging device captures or scans a set of physical color reference standards. These physical standards are also read by a spectrophotometer or colorimeter and the reference data are compared with the device data using the Color Management Profiling software to construct appropriate look-up tables.
The Source Characterization Profile data body from the imaging opera-tion of FLG. 1 is sent to a computer. FIG. 2 illustrates how the R, G, B i data are linked to L*a*b; data residing in the image's Source Characterization Profile. FIG. 3 illus-trates a second look-up table specific to the image reproduction device. This image re-production device look-up table consists of L*a*bi coordinates associated with appro-priate RaGzBx or CMYK values to form a Destination Characterization Profile.
Here the L*a'b* data are linked to RZGiB2 or CMYK data. FLG. 4 shows Color Manage-ment Module software chaining the Source Characterization Profile to the Destination 2S Characterization Profile via the Profile Connection Space. The L*a*b*
coordinates of the Source Characterization and Destination Characterization Profiles serYe as a Profile Connection Space used by the Color Management Module software in the computer.
Mapping of the image's color information by the Color Management Module is done by first using the Source Characterization Profile to convert the R,G~B~ data to L*a*b*.
This then enters the Destination Characterization Profile with L*a*b# and extracts ei-then an RZGZBZ or CMYK file to arrive at color codes specific to that device.
In es-sence, this enables the image input and image reproduction devices to communicate with each other in a common language. The image reproduction device will typically be a printer of some kind such as a laser or inkjet type or could even be a commercial printing press.
Color Management Profiling Software titay again be used for creating or modifying the printer look-up table in similar manner to that explained earlier. Quality control of the ultimate printed image is again achieved by using color reference stan-dards as an input tile. A colorimeter or spectrophotometer scans the printed output and the Color Management Profiling software compares it to the reference data, using the results to either construct or modify the look-up table. This is the method used prior to the present invention by the imaging community to correct for color inaccuracies intro-duced by the specifc device and medium employed.
By characterizing each specific medium for each specific image repro-duction device the need for adjustment by the medium customer is eliminated.
This is illustrated in FIG. 5 where two different printers are using two different media. It must be emphasized again that Destination Characterization Profiles are media dependent.
Different media will give different color renditions using the same printer.
I~owever, accurate color rendition may be achieved by cresting a Destination Characterization Profile (DCP) that is specific to both the printer and to the print medium employed.
"Color accuracy" includes, but is not limited to, colorimetric and perceptual rendering intents. Colorimetric accuracy ensures that the L*a*b" values for the reproduced ins age match the original image within the color gamut limitations of the device.
Percep-tual accuracy is aimed at obtaining an acceptable visual or appearance match even if colorimetric accuracy is relaxed somewhat.
In FIG. 5, DCP-I is used with printer type A using medium x and DCP-2 is used with medium y. Similarly, DCP-3 is used with printer B when print medium x is used. DCP-I and DCP-2 will compensate for the differences in media. DCP-1 and DCP-3 will compensate for the differences in printers using the same print medium.
Similar profiles are prepared for each medium and for each printer type.
It is unique in the graphic arts for a media vendor to supply custom Des-tination Characterization Profiles with their traditional media products.
Without such a product there is no method for ensuring consistent and accurate color reproduction since the media by itself can be thought of as its own imaging device. These Profiles wilt have been developed with full knowledge of the characteristics and variability within the particular grade of paper and knowledge of the characteristics and variability of the particular printer type that ~i11 use the product. Custom look-up tables specifi-cally tailored to the devices and media product represent a very significant advantage to the imaging community as a means of saving time and reducing rejected printed prod-uct or unprintcd media.
The present invention overcomes the limitation of the current methods S used for destination ch$racterization. Because the aew method explicitly incorporates media characteristics into the image reproduction system, the system is fully closed since all system components have been identified. Implementation of the method en-sures consistent and $ccurate color reproduction in hardcopy output regardless of the manufacturing variation in the media and output device.
10 The invention provides Media Characterization Pmfile software that rep-resents a significant advance over any generic correction for different media that the imaging device supplier might have been able to supply. The custom profiles may be supplied in numerous ways, e.g_, as scanner read labels on the medium shipment or by downloading from electronic transfer means such as the Internet.
The present invention should not be considered as limited to systems that convert initial RGB values to a common language; e.g., L*a*b* via the Profile Connection Space. The oppominity exists for developments that will enable image in-put devices to communicate directly with image reproduction devices without the need for embedding a profile. This could be the case if in the future the color encod-ing/exchange architecture way modified so that all images were encoded and exchanged in Profile Connection Space (PCS) units. An example might be calibration in [RGB)~$ rather than the present device dependent units. Further, the invention is not limited to color reproduction as the term "color" is usually considered. The customized Destination Characterization Profiles of FIG. 5 are capable of encoding various ren-dering features such as reducing a color image to black and white or duotone.
Con-versely they may be used to enhance a black and white image by converting it into duotone or pseudo color. The invention is also useful for rendering black and white input images into black and white output images. All of these variations are considered to be encompassed within the teem "color reproduction", It will also be understood that CIE XYZ. CIE L*C*H*, or other color descriptions are suitable and the invention is independent of the color definition used for the ProFle Connection Space.
Nor is the invention limited to reproduction devices having only a three or four color system.

Examcle_ The following example illustrates the steps used in preparation of a customized Destination Characterization ProFle for one selected paper grade and printer. No particular products need be specified since the method is applicable to all different grades of media and all types and brands of printers receiving digital inputs.
For convenience in the present example assume an inkjet printer and an appropriate mufti-use paper. Characterization will normally be done by the paper supplier who will have full access to data regarding the paper source; e.g., mill location or specific paper machine within the mill, date of manufacture, changes in chemistry or furnish, and any other variables that might af~'ect paper performance. The series of steps will be re-peated for each grade of paper to be used with a given printer and again for all of the various grades to be used with a number of different printers.
FIGS. 6A and 68 illusuate graphically the process now to be described.
. Step 1. A paper grade is selected. Randomly selected reams of paper are chosen for testing using statistically valid sampling techniques.
Step 2. Select P printers of a given type. Verify the device to be in a calibrated state and linearized_ Step 3. Assemble from two to four printers P of the selected type and provide two to three full sets of ink cartridges R to be used with each printer. Assume for this example that three nominally identical printers with two nominally identical ink cartridge sets per printer will be tested (printers P = 3 and ink cartridges R
= Z).
Step 4. Choose representative samples M of the paper grade. These samples will include the major sources of manufacturing variability; e.g., source, date, etc., as was noted above. For the present example, let us assume that the sample in-eludes paper drawn from three different production runs at each of mill locations A and B. In this case M= 6 classes.
Step 5. Randomly assign and equally distribute the ink jet cartridge sets to the P printers so that each printer has R = 2 sets of cartridges. Install the first set of cartridges into each printer. Randomly assign the M= 6 paper classes to the printers. In this case two classes will be assigned to each printer.
Step 6. Print a color reference target_ A suitable reference is the industry standard IT8 digital file consisting of several hundred color swatches. This first pass will yield 6 prints (3 printers each with two paper samples).

Step 7. Eor each of the above prints use any of the commercially avail-able Color Management Profiling software packages and a spectrophotometer to meas-ure the desired color rendering properties. In this example L*a*b* values were meas-ured for each swatch resident in the color reference target. Store the L*a*b*
values S cottesponding to each RGB triplet or CMYK quadruplet in a digital file.
Step 8. Remove the ftrst set of colorant cartridges and install the second set for all three printers.
Step 9. Repeat steps 6-8.
Step 10. When all color measurements have been completed a total of MR (6 X ?) or 12 Profile Connection Space measurement files v~iill have been created.
Step I 1. Poot the data from all MR files. For each color swatch calculate and store the average values of the L*a*b* parameters. The median is the preferred measure of central tendency.
Step 12. Construct the averaged Profile Connection Space measurement file by assigning the average value of L*a*b* for each color swatch entry.
Step 13. Again use cocrunercial Color Management Profiling software to process the data file created in Step 12 to construct a print medium specific Custom Destination Characterization Profile.
Step 14. fivaluate the Custom Destination Characterization Profile by Visually examining color reproduction quality on selected sheets of stock representative of the range of variability used in the above medium-device ch~aracterizstion analysis.
Appropriate evaluation images are those that showcase various hardcopy reproduction challenges.
Step I S. If the Custom Destination Characterization performs ade-quately, the product is complete and ready for dissenvnation. If not, the Profile Con nection Space measurement is again analyzed and the Custom Destination Chatacteri-zation Profile modified as necessary until visual and instrumental performance criteria are met.
It will be evident that variatioru in the process not described herein 3d might occur to those skilled in the art. The inventors regard these variations to be in-cluded within the scope of their invention if encompassed within the following claims.

Claims (19)

1. A product for printing which comprises in combination a bundled specific printing medium and custom Destination Characterization Profile for a specific printing device using the medium.

2. The product of claim 1 in which the custom Destination Characteriza-tion Profile is derived by determining the known variability in color rendering proper-ties of the specific medium on the given printing device and assigning an average value for the properties.

3. The product of claim 1 in which the custom Destination Characteriza-tion Profile is supplied as a computer compatible format.

4. The product of claim 3 in which the computer compatible format is a floppy disk.

5. The product of claim 3 in which the computer compatible format is a CD-ROM.

6. The product of claim 3 in which the computer compatible format is accessible from an Internet Web site.

7. The product of claim 1 including a label which provides a code or key to locating an appropriate custom Destination Characterization Profile.

8. The product of claim 7 including a UPC bar code.

9. The product of claim 1 in which the custom Destination Characteriza-tion Profile is located in a computer operating system.

10. The product of claim 1 in which the custom Destination Characteri-zation Profile is located in a printer drier.

11. The product of claim 1 in which the custom Destination Characteri-zation Profile is located in a caster image processor.

12. The product of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 in which the medium is paper.

13. The product of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 in which the medium is a paper-like substrate comprising a synthetic polymer.

14. A method of ensuring accuracy of color reproduction in printing which comprises:
(a) providing a specific printing medium;
(b) determining the known variability in color rendering properties of the specific medium on a given printing device and assigning an average value for the properties;
(c) constructing at least one custom Destination Characterization Profile to characterize a given-type printing device for the specific print medium using said average value of medium color rendering properties, said custom Destination Charac-terization Profile or Profiles interacting with other printing device software to ensure that the final printed image corresponds in color rendition to the image source; and (d) repeating steps (b) and (c) for each type of printing device that will use the medium thereby creating custom Destination Characterization Profiles for each of the printing devices.

15. The method of claim 14 which further comprises providing the cus-tom Destination Characterization Profile or Profiles for each specific printing device using the medium so that consistent color reproduction accuracy will be obtained re-gardless of the printing device using the medium.

16. The method of claim 14 in which the printing device is in a known state of calibration and has been linearized.

17. The method of claim 15 in which the printing device is in a known state of calibration and has been linearized.

18. The method of claims 14, 15, 16, or 17 in which the medium is pa-per.

19. The method of claims 14. 15, 16, or 17 in which the medium is a paper-like substrate comprising a synthetic polymer.