Color Yield

• Ink and Toner

  Color adds significant complexity. As with monochrome, meaningful color yield measurement also requires testing with a representative (of the intended market) color test document, specified as a digital computer file. For the last few years all Microsoft Office (and many other) documents are in sRGB color space, a calibrated RGB. It is therefore quite desireable to use an sRGB-based test document standard. Creating such documents in a device-independent manner is an interesting challenge. (The SpencerLab Printer Test Suite includes suitable representative color test documents.)

  Since it is quite rare that a printer will print with RGB colorants, RGB documents must be converted into CMYK colorants within each printing device. If each printer's conversion algorithms (equations, lookup tables, etc.) were known, the resultant CMYK could be calculated—but each printing device incorporates its own proprietary RGB to CMYK conversion, and the conversion may be different in sparse areas than in solid coverage areas. Issues such as Gray Component Replacement, UnderColor Removal, and UnderColor Addition may have very significant impacts on yield. These functions are very device-dependent, and are often subject to driver settings.

  Coupled with the fact that the yield may vary considerably page-to-page on many printing systems, testing must involve actual testing of representative sample cartridges, with results representing the statistical average of multiple tested cartridges on multiple printers.

  Measurement of color yield further requires that the number of prints that are achieved from each color cartridge be measured simultaneously while printing the same test document.

  ISO/IEC

  As with monochrome toner cartridge testing, a consistent definition of cartridge “end-of-life” is required. This definition needs to respect the fundamental differences between ink-based and toner-bassed color printing devices, while retaining the ability to compare one to the other.

  The ISO/IEC committees are currently drafting a set of three standards for color ink and toner cartridge testing, tentatively entitled: "Method for the determination of toner cartridge yield for colour electrophotographic printers and multi-function devices that contain printer components" (19798); "Method for the determination of ink cartridge yield for colour inkjet printers and multi-function devices that contain inkjet printer components" (24711); and "Color Test Pages for Measurement of Office Equipment Supply Yield" (24712).

  SpencerLab has created a representative color test document standard (also included in the SpencerLab Printer Test Suite), and has been performing color ink and toner yield testing for over a decade. Our work and our executive staff have contributed significantly to the development of ISO/IEC color yield test standards for Ink, Toner, and a common Standard Test Document and Color Test Suite.