IS&T©s 2000 PICS Conference IS&T©s 2000 PICS Conference Copyright 2000, IS&T Silver Halide Print Media for Direct Digital Writing Jack Rieger Eastman Kodak Company Rochester, New York USA Abstract image sensor, while ‘silver halide capture’ assumes a conventional camera containing film. ‘Digital hardcopy’ Traditionally, the word ‘digital’ is not used in combination usually refers to inkjet, thermal, and electrophotographic with the words ‘silver halide’. If it is digital, prevailing technologies, while ‘silver halide hardcopy’ usually refers to wisdom assumes that it is not silver halide, and vice-versa. analog optical printing using conventional enlargers or This assumption is now faulty, for excellent results in printers. digital imaging can be obtained with silver halide capture and output. This talk will discuss the technology of digital Strength of Silver Halide silver halide output. The term ‘digital’ should not exclude silver halide Eastman Kodak Company has been interested in direct technology. ‘Silver halide’ can be a subset of the ‘Digital’ digital exposure onto silver halide media for many years. In category. The strength of silver halide in image capture is its the last few years, consumer and professional photographic ability to record high resolution at low cost, and its archival laboratories have begun to realize the advantages of direct optical storage capacity. For digital output, there is room in digital writing onto color photographic paper. We have now the industry for multiple technologies. Each of these has its introduced multiple generations of digital silver halide paper own strengths and weaknesses. The strength of silver halide and digital silver halide display film. These formulations in digital hardcopy is its continuous tone quality, high have been optimized for digital exposure, and have given us imaging speed, and low media cost. This talk will discuss information about some of the unique requirements for silver the technology of digital silver halide output. halide media when exposed in digital printers. Our latest product offering gives our customers the highest level of History quality and the broadest range of digital performance for a silver halide media. Early Adopters Direct digital writing to silver halide print materials Eastman Kodak Company has been interested in direct offers the advantages of digital while maintaining the image digital exposure onto silver halide media for many years. quality, cost, and productivity advantages of traditional Early adopters include the graphics industry where digital photographic output. We believe that this area will allow separations are generated using laser exposed silver halide our customers to offer new products and services that were media. Professional laboratories use small format digital not previously available, which will further enhance their imaging to create reversal film for direct viewing or negative business. film for use in the traditional optical printing process. Now, the term ‘digital’ does not leave silver halide Commercially available silver halide print exposing technology behind. It embraces silver halide, offering engines have been available for many years. Early engines another hardcopy output choice to the digital lab. were based on CRT technology, producing low-resolution index prints or digital images 8 × 10 and smaller. These Introduction printers relied on using optical papers, as there were no digital papers available at the time. Since pixel exposure Digital vs. Silver Halide times are within the range of high-speed printing, no adverse Digital imaging is the technology in the spotlight problems with sensitometric response were observed. today, for many reasons. Its strengths include instant soft display at point of capture, image quality optimization, Explosion of Print Engines and Media image customization, electronic communication, and no In the 90s many other exposing light sources were messy photochemicals. Silver halide technology is the introduced in these digital silver halide printers. These imaging media of choice when high quality is needed at an include tungsten, laser, and LED. These sources varied economical price point. dramatically in their total light output, spectral light output, When capture and hardcopy are considered, two and pixel exposure time. Also, the various printer designs groupings usually emerge: digital and silver halide. ‘Digital featured customized pixel overlap, number of exposures per capture’ usually assumes a camera containing a solid state pixel, time between exposures per pixel, exposure 101 IS&T©s 2000 PICS Conference IS&T©s 2000 PICS Conference Copyright 2000, IS&T uniformity across the printing surface, media transport Design Considerations technique and accuracy, pixel scanning technique and accuracy, etc. These unique characteristics set these printers The silver halide media in a digital system plays a different apart from one another, but made media design problematic. role than in a conventional analog imaging system. Some Early digitally optimized silver halide products include important design elements for these two systems are KODAK PROFESSIONAL Digital Paper, Type 2933 and compared in the table below: KODAK PROFESSIONAL Digital Paper, Type 2976. These products compensated for the changes made in these Design Elements of Digital vs Conventional digital printers, and were quite successful in this emerging Media marketplace. Attribute Conventional Digital In the last few years, consumer and professional System System photographic laboratories have begun to realize the Tone Determined by the Determined by advantages of direct digital writing onto color photographic Scale media software, within print media, both reflection and transmission materials. media/printer limits Reflection materials include not only paper, but also flex, a of minimum density stiff white plastic material used for commercial displays and and maximum density ID cards. An example of this is KODAK PROFESSIONAL Color Determined by the Determined by DURAFLEX Digital Print Material. Transmission materials Repro- media software, within include Trans and Clear. These are used on a light box, and duction media/printer limits viewed with transmitted light. The Trans product has a built of color gamut in white diffuser, so is used on a light box with a clear glass Color Determined by Determined by front. The Clear product does not incorporate any diffuser, so Purity image dye of spectral quality of is used on a light box with a diffused front. Examples of negative, spectral printer illuminant these include KODAK PROFESSIONAL DURATRANS quality of printer and media design Digital Display Material and KODAK PROFESSIONAL illuminant, and DURACLEAR Digital Display Material. media Sharpness Determined by the Determined by Digital Imaging of Silver Halide media and printer software, printer, and optics media Digital silver halide materials are exposed in a digital writer using photons of light of various intensities and colors Text Typically added Determined by determined from a digital file. The digital file could have a quality post process software, printer variety of origins, including scanned film and prints, resolution, and media computer graphics, and digital camera images. design After Raster Image Processing (RIP), the computer tells Reciprocity the printer how much red, green, and blue light to use to Digital printing is characterized by a wide range of pixel expose the media. Exposures are typically made one pixel at exposure times. These exposures are typically high intensity a time using laser, LED, CRT, or some other type of light and short duration, relative to optical exposures. A decade source. With laser printers, red, green, and blue laser beams chart of exposure times for optical and digital silver halide are typically combined into a single beam, then scanned papers is presented in Figure 1. across the media. In some printers, the media moves in the y Optical papers at Eastman Kodak Company are direction while the scanning occurs in the x direction. In optimized for optical exposure times, depending on the other printers, the media is held stationary while it is customer application. Digital papers for use in CRT, LED, scanned in both directions. and LASER devices are optimized for the relatively short The media must then be processed conventionally, duration exposure times. An emulsion’s response to light of converting non-visible latent image to a chromogenic print varying duration is commonly referred to as the reciprocity using photographic image dyes. For the media discussed response of the emulsion. Emulsions in Kodak’s optical here, Process RA-4 or one of the Process RA-4 derivatives papers have historically lost speed and gamma with digital is used. exposure times. Figure 2 illustrates the sensitometric Before an image can be printed, a calibration of the response of an optical media, KODAK EKTACOLOR Edge media on the printer must be completed. This process maps 7 Paper, to optical and laser exposure. This product the developed density of the media to discrete power levels in exhibited significant density loss and irregular sensitometric the printer light source. Several iterations of expose/print/ response when exposed with a laser, but of course had process/densitometer/calculate are often required to adjust excellent results with an optical exposure. power levels of the printer to fit a preset sensitometric aim. 112 IS&T©s 2000 PICS Conference IS&T's 2000 PICS Conference Copyright