P H O T O CD I N F O R M A T I O N B U L L E T I N

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1 PCD 077 Juy, 1994 Copyright, Eastman Kodak Company, 1994 P H O T O CD I N F O R M A T I O N B U L L E T I N Fuy Utiizing Photo CD Images Maintaining Coor Consistency When Creating KODAK Photo CD Portfoio Discs This artice is the fifth in a series in which we wi discuss seected topics covering the imaging science of the Photo CD system. The goas of this series are to further your understanding of the Photo CD system and to provide you with information hepfu in producing the maximum quaity for each Photo CD image. In this artice we describe some image quaity issues and recommendations to use when creating Kodak Photo CD Portfoio discs. Background Initiay, a Photo CD discs (i.e., KODAK Photo CD Master and KODAK Pro Photo CD Master) were created on a dedicated system where the ony input was fim. With proper ab practices, a Photo CD images exhibit simiar tone and coor reproduction making them compatibe with each other. With the introduction of Portfoio Photo CD, users can store any computer-created or computer-modified fies to a KODAK Photo CD Portfoio Disc. In most cases, the coor and tone reproduction of these images is expected to be compatibe with images on a other KODAK Photo CD Discs on the market (i.e., KODAK Photo CD Master Disc, KODAK Pro Photo CD Master Disc, etc.). In a typica mutimedia workfow, customers wi use creative packages (e.g., KODAK Photo CD Access Pus Software, ADOBE PHOTOSHOP Software, ALDUS PHOTOSTYLER Software, KODAK Create-It Photo CD Presentation Software, etc.) to produce graphics or modify existing images. These images wi be saved in fies and become assets for software products Artice No. 5 (e.g., KODAK Arrange-It Photo CD Portfoio Layout Software or KODAK Create-It Photo CD Presentation Software) where the user interactivity is added. This interactivity incudes image sequencing, audio, and branching through menu seections. After competing this creative step, a script is written and sent with the images and audio to a service bureau that can write KODAK Photo CD Portfoio Discs. Using the KODAK Buid-It Photo CD Portfoio Disc Production Software, this service provider creates a Photo CD Portfoio Disc from these assets. This disc can be payed on computer patforms, KODAK Photo CD Payers, CD-I payers and 3DO payers. Furthermore, the disc coud be submitted to a disc mastering company for mass repication of inexpensive pressed discs. Another use of Portfoio Photo CD is the storage of any digita image in the Photo CD format. These images can be modified images from Photo CD Master Discs, computer-generated images, images scanned from fim, etc. For exampe, you can read an image from a KODAK Photo CD Master Disc into ADOBE PHOTOSHOP Software using the KODAK Photo CD Acquire Modue and combine it with other images, text or graphics. After this creative work, the image can be saved in either TIFF or PICT format and deivered to the service provider for conversion to a Photo CD disc. By converting to a Photo CD Portfoio Disc, you can everage the mutipatform capabiities of the Photo CD format and the wide variety of Photo CD enabed products. Incuding images from a wide variety of sources or input devices creates a potentia for inconsistent image quaity. Simiar to preparing image data for devices such as printers, the Photo CD Portfoio image must be propery prepared so the data is consistent with other Photo CD discs. This artice wi focus on the issues

2 and recommendations required for maintaining the image s coor and tone reproduction quaity. Buid-It Version 1 Coor Encoding Expectations One of the functions of the KODAK Buid-It Photo CD Portfoio Disc Production Software is to read RGB or PHOTOYCC fies in TIFF or PICT format, convert them to PHOTOYCC, and store them as IMAGE PAC Fies on a Photo CD Portfoio disc. To convert images from one device to another, it is critica to have the data describing the coor aspects of the source device to achieve high quaity resuts. Currenty, there are no universay impemented methods of storing an image s reference coor information in a digita fie. Some improved methods are becoming avaiabe, but the vast majority of fies today have RGB information with no additiona information specifying the origin of that data. In KODAK Buid-It Photo CD Portfoio Disc Production Software, Version 1, two coor metrics can be used. A coor metric is the set of three vaues that describes the coor information in a pixe. Most usefu metrics have a specific coor definition which aows subsequent software or hardware products to produce a high quaity image. The first metric used by Buid-It is RGB (in either TIFF or PICT format), where it is assumed that the RGB is consistent with a gamma 2.2 monitor, D6500 white point, and monitor phosphors defined in the CCIR 709 standard. These criteria aow a simpe conversion to PHOTOYCC. If an RGB TIFF fie is created on a system with a significant departure from these criteria (e.g., gamma 1.8), the images wi retain that undesired bias. For exampe, in the gamma 1.8 condition, the user woud obtain a Photo CD image which woud have a higher contrast or gamma than desired because the TIFF data was originay intended for a ower gamma monitor. The second metric is PHOTOYCC where Y is stored in the R channe, C1 is stored in the G channe and C2 is stored in the B channe. If your creative system can convert your image to PHOTOYCC, the data can be stored on a Photo CD disc without any additiona coor conversion. In the future, a set of industry-defined TIFF tags, which enabe the storage and recognition of PHOTOYCC, wi be used. Very few systems today have been updated with these TIFF tags, however there are workarounds that can be used immediatey. By converting to PHOTOYCC, the image originator can use a of the benefits of this coor encoding metric. These benefits incude a coor gamut and dynamic range which can encompass a fim and scene coors, and thus not be imited by today s typica monitor-based RGB metrics. Monitor Caibration In order to use the computer monitor as an accurate coor reference, it shoud be caibrated to a specific white point and gamma setting. If these variabes are not controed, the state of the monitor may introduce a bias which coud be carried through to the Photo CD Portfoio Disc or any other output device (e.g., printers or fim writers). To minimize these probems, a monitor caibration system must be used. Severa manufacturers produce devices that measure the characteristics of a monitor and downoad information to a dispay board to bring the monitor to a known position. For those who require very high precision, they shoud purchase monitors which are hardware caibrated cose to where they wi be used, otherwise the software caibration may introduce undesired artifacts (e.g., quantization) in extreme cases. At the very east, the user shoud use some type of visua adjustment toos (e.g., Kno Gamma INIT for APPLE Macintosh Computers) to pace the monitor coser to the aim position. These toos are not perfect but are better than using uncaibrated out of the box equipment. When using creative packages to prepare fies for Photo CD Portfoio Discs, the user shoud set the caibration too and software preferences for gamma 2.2, D6500. By doing this, they are working with and viewing the image in an RGB space which is consistent with the RGB that Buid-It expects. 2 Maintaining Coor Consistency When Creating KODAK Photo CD Portfoio Discs

3 Viewing Conditions Monitor viewing conditions are as important to consistent quaity as monitor caibration. Many users examine their creative work in viewing conditions that may bias their resuts. The biggest factor is viewing fare. Fare is caused by ambient ights which shine on the monitor surface, thus reducing the image s apparent contrast. Typicay, the user wi raise the contrast of the image and wi then be disappointed when the print or Photo CD Portfoio Disc has too much contrast. Coored iuminants wi affect the coor appearance of the image on the screen. Monitors shoud be used in subdued ighting so that the image shadows are controed by the CRT and not affected by the gare from the room ights. One exampe of poor ighting is standard office environments which use bright fuorescent overhead ights that have a greenish cast. Another exampe is to position a monitor near a window where sunight iuminates the monitor. In this case, the user wi obtain different resuts depending on the time of day or the weather outside. In genera, the room ighting shoud e subdued, but shoud aow one to work safey and efficienty. Use indirect ights of approximatey 5 ux (i.e., eiminating refections on the monitor surface). As a reference, typica office ighting can be times this recommendation. Coor temperature of these ights shoud approximate dayight. Coo White Deuxe fuorescent tubes are suitabe. To avoid coored refections, surrounding surfaces shoud be a matte neutra gray, and users shoud avoid wearing white or brighty coored cothing. Using KODAK Photo CD Master Discs in Creative Appications When using Photo CD discs as input in appications that wi eventuay resut in a Photo CD Portfoio Disc, keep the foowing in mind: First, foow the suggestions mentioned in the previous sections. Otherwise the images wi retain some undesired monitor or viewing environment bias. Next, be aware that there are an ever-increasing variety of software and hardware products that can dispay a Photo CD image. Many of these products have user adjustments that attempt to compensate for the monitor and viewing conditions which wi cause probems when creating a Photo CD Portfoio Disc. For exampe, the KODAK Photo CD Acquire Modue for ADOBE PHOTOSHOP Software and KODAK Photo CD Access Pus Software provide a variety of ook-up tabes which shape an image for a particuar monitor. Unfortunatey, a high contrast ook-up tabe may be fine on this specific monitor, but when the image created by this tabe is sent to another device that doesn t compensate for this bias, a poor resut wi be obtained. A new tabe has been created which minimizes the adjustment for monitor characteristics and is recommended for use when reading Photo CD discs for Portfoio use. This tabe is caed PORTFOLIO and is more consistent with the RGB coor metric expected by KODAK Buid-It Software. Images shoud ook peasing on a monitor set to gamma 2.2 and D6500. This new tabe is avaiabe on CompuServe (GO KODAK) and Internet. Using the other pug-in tabes to improve poor origina images is fine as ong as the monitor is setup to gamma 2.2 and D6500. Many appications which do not document their RGB rendering produce images in which highight information has been ost and at times coud cause cooration in bright areas (i.e., sometimes this RGB is caed Video RGB ). Fortunatey, the mid-scae contrast is consistent with the RGB that Buid-It expects and wi serve for ess demanding appications. This same mid-scae contrast may not be appropriate for use in more critica appications. Some appications incorporate the KODAK Precision Coor Management System for accessing Photo CD images such as the KODAK Coor Management System Photo CD pug-in shipped with ADOBE PHOTOSHOP Software. It aows the user to customize the conversion from YCC to a variety of coor spaces by seecting Precision Transforms (PT) for both source and destination. The defaut source PTs are seected based on the type of origina and how it was scanned (Negative vs. 3 Maintaining Coor Consistency When Creating KODAK Photo CD Portfoio Discs

4 Universa E-6 EKTACHROME). The defaut destination PTs incuded with PHOTOSHOP are targeted at PHOTOSHOP RGB with a Gamma 1.8 and D5000 white point or at PHOTOSHOP L*a*b*. Optiona destination PTs can be added to the KPCMS foder and aow for conversion directy to CMYK as we as to other target RGBs. KODAK s CMS Group wi reease a Portfoio (Gamma 2.2, D6500) destination PT which can be used to open YCC images into a space which is consistent with the RGB expected by Buid-it. This PT wi be posted in KODAK s AOL and CompuServe (GO KODAK) forum ibraries. Another option occurs when the image manipuations are restricted to cropping, padding, resizing and coning. In these situations, the coor and tona content of the images is NOT being adjusted. To maximize the fina image quaity, we recommend accessing images by using the PHOTOYCC metric avaiabe in the KODAK Photo CD Acquire Modue for ADOBE PHOTOSHOP Software or KODAK Photo CD Access Pus. The uma information (Y) is read into the Red channe and the chroma information (C1 and C2) are read into the Green and Bue channes. The image wi ook greenish and quite unusua but, by examining the Red channe (i.e., uma), one can usuay perform a of the noted image manipuations. By working in PHOTOYCC, one retains a of the inherent coor and tona range. After work is compete, store the image in a TIFF fie and be sure to write down which fies are in the PHOTOYCC metric. When the fies are dropped off to a Buid-It service provider, incude this written information so the provider can process the images propery. Some handy PHOTOYCC vaues for padding images incude: Y C1 C2 Highight white Diffuse white % gray Back Using Other Image Sources in Creative Appications When working with images from sources other than Photo CD master discs, many of the same guideines are important. The monitor shoud be set to D6500 and gamma 2.2 so that the resutant RGB images are consistent with the metrics that KODAK Buid-It uses. Further, as mentioned earier, the viewing conditions shoud be maintained so that they don t infuence your coor or tone reproduction decisions. Finay, any scanner attached to the system shoud be setup so that it converts the scanned data to a gamma 2.2, D6500 dispay system. For computers that utiize the KODAK Precision Coor Management System, output profies wi be deveoped to convert the dispayed images to metrics that are consistent with KODAK Buid It Software. These profies wi aow one to work with any supported monitor setup and produce compatibe output fies. Other coor management systems may aow for conversion from your preferred monitor setup (e.g., D5000, gamma 1.8) to the setup that Kodak Buid It Software expects. After editing the image for a peasing reproduction, it shoud be stored as a RGB TIFF fie and deivered to the service provider. This RGB TIFF fie wi be converted to PHOTOYCC format and stored as an IMAGE PAC fie onto a Photo CD Portfoio disc. 4 Maintaining Coor Consistency When Creating KODAK Photo CD Portfoio Discs

5 Summary of Recommendations When doing creative work that wi be subsequenty used on a Photo CD Portfoio Disc and compatibiity with other Photo CD discs is desired: Use a monitor caibration too and set the monitor to a gamma of 2.2 with a white point of D6500. Use subdued ighting for your computer system. Avoid windows or bright overhead fuorescent ights as they wi infuence the appearance of the image on the monitor. When using Access Pus or ADOBE PHOTOSHOP Software /KODAK Photo CD Acquire Modue 2.0.1, choose the PORTFOLIO ook-up tabe. When using KODAK Precision CMS to open your images in PHOTOSHOP or PHOTOSTYLER Software, a new Destination Transform shoud be used that wi be avaiabe in the future. The current transform to RGB in PHOTOSHOP is not recommended. If performing spatia operations such as resizing, cropping, padding and even coning, access the image in the PHOTOYCC metric for better image quaity. Though the image has an unusua appearance, a of the coor and dynamic range of PHOTOYCC format is retained. When obtaining data from other devices (e.g., scanners) first adjust their settings to produce data consistent with a gamma 2.2, D6500 dispay device, whenever possibe. When using an image from a device whose specifications are known to be anything other than gamma 2.2 and a white point of D6500, examine the image on a system setup to gamma 2.2/D6500 and modify the image as required. Industry Directions As coor management capabiities become part of every computer operating system, many of these issues wi become transparent to the user. Ideay, these systems wi know the characteristics of your scanner, monitor and output device. With this information, consistent coor shoud be maintained. Today, there are some standaone systems which provide this capabiity. For exampe, the KODAK KEPS PCS100 Imaging Station provides coor management aimed at the printing and pubishing market for an APPLE MACINTOSH System. Summary By foowing the outined recommendations, the open environment of Photo CD Portfoio discs can produce discs which are consistent with a other Photo CD formats. Using these guideines wi hep maximize quaity and minimize your frustration. References 1. Using Information Beyond 100% White, Artice No from the Fuy Utiizing Photo CD Images series, Eastman Kodak Company, 1993, PCD KODAK Photo CD Products, A Panning Guide for Deveopers, Eastman Kodak Company, Part No. DCI200R 3. Universa Fim Terms for Reversa Fims, Artice No. 2 - from the Fuy Utiizing Photo CD Images series, Eastman KODAK Company, 1993, PCD Adjusting the Baance of Images, Artice No. 3 - from the Fuy Utiizing Photo CD Images series, Eastman Kodak Company, 1993 PCD PHOTOYCC Coor Encoding and Compression Schemes, Artice No. 4 - from the Fuy Utiizing Photo CD Images series, Eastman Kodak Company, 1994, PCD Maintaining Coor Consistency When Creating KODAK Photo CD Portfoio Discs

6 Photo CD Information Buetins are pubished by Marketing Technica Support. They provide information of imited or specific appication. Responsibiity for judging the appicabiity of the information for a specific use rests with the end user. PCD077 Juy 1994 CD Imaging Eastman Kodak Company Rochester, NY Kodak, Image Pac, PhotoYCC, and Ektachrome are Trademarks The Photo CD symbo is for use by Kodak and its icensees ony and may not be reproduced without permission from Kodak.