(Message inbox:4875) Received: from sprite.Berkeley.EDU (allspice.Berkeley.EDU) by cdrom.com (4.1/SMI-4.1) id AA25346; Tue, 9 Nov 93 08:03:05 PST Errors-To: KNEXMAILER@knex.via.mind.org Received: from emory.mathcs.emory.edu by sprite.Berkeley.EDU (5.59/1.29) id AA331360; Tue, 9 Nov 93 08:04:08 PST Received: from uumind.UUCP by emory.mathcs.emory.edu (5.65/Emory_mathcs.3.4.12) via UUCP id AA28262 ; Tue, 9 Nov 93 11:01:19 -0500 Return-Path: KNEXMAILER%knex.UUCP@mathcs.emory.edu Received: by mind.ORG (1.65/waf) via UUCP; Tue, 09 Nov 93 10:24:01 -0500 Received: by knex.via.mind.org (1.65/waf) via UUCP; Tue, 09 Nov 93 04:37:02 EST Resent-Date: Tue, 09 Nov 1993 04:33:28 -0800 Resent-From: KNEXMAILER@knex.via.mind.org Received: by knex.via.mind.ORG (V-MailServer 2.21) id VT58038; Tue, 09 Nov 1993 04:33:28 -0800 Date: Mon, 08 Nov 93 22:36:36 EST From: neka@aol.com Subject: PhotoCD vs Highend scans Sender: MAILSERV@knex.via.mind.ORG To: CD-R & CDRom Publishing Discussion List Message-Id: <9311082236.tn36990@aol.com> Reply-To: CD-R & CDRom Publishing Discussion List Errors-To: KNEXMAILER@knex.via.mind.org Precedence: bulk Resent-Message-Id: Hi all, Here's a tidbit of information on Photo CD from Kodak. I wrote the following article for a local prepress trade publication in late July of this year. I gives some insight to the generation of Photo CD images. Hope you find the information fun and useful :) Neka While Compact Disc - Read Only Memory (CD-ROM) storage technology has been in widespread use for a number of years, the emergence of Kodak's Photo CD technology may prove to be the biggest ambassador of compact disc technology to-date. Photo CD will help other Compact Disc (CD) technologies, such as Compact Disc - Interactive (CD-I) and Full Motion Video (FMV) on CD to gain a foothold, helping them to become as commonplace in U.S. homes as the omnipresent videocassette recorder. When Kodak first introduced the Photo CD player in late 1990, Photo CD was envisioned as the beginning of paperless photography. Connected to television set or color monitor, the Photo CD player allows a user to display digitally encoded photos, and can even provide limited special effects, such as controllable zoom and pan of each image. Almost immediately, color publishers saw it as an inexpensive means of acquiring high resolution scans. At less than two bucks a piece, Photo CD images are truly a bargain when considering the quality of the image. Each Photo CD image is stored on the disk as an "Image Pac" at five different pixel resolutions--192 by 128, 384 by 256, 768 by 512, 1536 by 1024, and 3072 by 2048 using a color encoding system known as YCC. Presently, Photo CD images can only be generated from 35mm film negatives or slides. Kodak just began shipping a larger format scanner to photofinishers which will generate Photo CD images from 2 1/4 and 4 by 5 transparencies. Known as Photo CD Pro, the new format is being developed specifically to address the needs of professional photo labs and color prepress firms. Kodak's original vision was to have images scanned to look like the original scene. Referred to as scene space, the objective was to render the picture to meet the viewer's expectations, or, as the viewer remembered the scene in the minds eye. Many professional photographers objected to the scene space approach. Professional photographers make conscious decisions about a film's color tendencies and how that will affect the final image. Using the scene space approach negated their conscious selection of film type. In response, Kodak released two "universal" film term specifications, one for Kodachrome and one for Ektachrome. The film terms are designed to preserve the tendencies of the original color transparencies. The primary difference between highend scans and Photo CD is the scanning technology use for generating a Photo CD image. The Photo CD scanner uses Charge Coupled Device (CCD) mechanisms. Thus, Photo CD suffers from the same deficiencies in capturing shadow and highlight detail as does the typical desktop CCD scanner. Photo Multiplier Tube (PMT) drum scanners have a greater density range (0.0 to 3.9) which allows them to capture more detail in the shadows and highlights. In effect, more detail equals more data, and more data yields better picture quality. Secondly, and a bit more complicated, Photo CD images are designed to be viewed on a television using Kodak's YCC format. To bring a Photo CD image into your favorite image editing application on the computer, a conversion must take place. Kodak first released a conversion utility called Photo CD Access which converts native YCC to RBG format. Kodak also offers PhotoEdge, which adds some additional image manipulation capabilities. However, the YCC to RGB conversion performed by either Photo CD Access or PhotoEdge does not provide an accurate conversion of the original image. The poor conversion is due to the algorithms used to convert the image, which assumes the target conversion is RGB video, or simply put, broadcast video . Unfortunately, images prepared for broadcast video don't reproduce well for print. Users will experience a gain in the mid-tone values, and a clipping of highlight values. Additionally, image s converted using Photo CD Access or PhotoEdge are optimized for a white point of 6500o K as opposed to the standard prepress viewing environment of 5000o K. The white point differential between the two standards will show up as an off-color image when printed. To address the short-comings of Photo CD Access and PhotoEdge, Kodak also provides a new plug-in for the Macintosh called Photo CD Acquire. For $59.95, Photo CD Acquire allows the user to set white point and gamma targets. CD Acquire also provides for image cropping, color correction, and monitors targets which optimize conversion algorithms. Adobe Photoshop 2.5 allows for the acquisition of Photo CD images through it's "Open As..." menu selection. However, be aware that while it functions similarly to Photo CD Access, it doesn't provide the same options as Photo CD Acquire. The last important consideration that must be accounted for concerns the conversion process as well. One must remember that every time an image is converted into a different color space, YCC to RGB to CMYK, data is lost. The Long and Short of it... A word of caution to art directors, designers, and prepress production personnel. The old saying "You get what you pay for" definitely holds true here. High-end drum scans are still the way to go for critical, high-quality color work, and Kodak agrees. Photo CD images are great for pleasing color-budget-minded publications such as catalogs and spec sheets. In fact, the economy of Photo CD images allows designers and other electronic image developers to produce four-color publications when they could not have done so before.