All of the images included in this series were originally 35 mm transparencies-- a mix of KODACHROME and KODAK EKTACHROME Films. We created the digital images offered here using the process described in the steps below.
We transferred the original slides to Photo CD using a KODAK PCD Imaging Workstation 2400 (PIW). The PIW is a Photo CD authoring system consisting of the following components:
The PIW is designed to make scanning easy, fast, and reliable. Exposure and focus are automatic. Color balance is set through the selection of "film terms"-- special sets of data that interpret the color information collected by the PIW's scanner. Film terms take into account characteristics particular to various film types, and play a vital role in optimizing scan quality. We used the "Universal E- 6" and "Universal K-14" film terms in order to provide a faithful representation of the original transparencies.
We checked slides for dust before scanning. This precaution saved time in digital spotting later.
The images are in a compressed digital form on the Photo CD, and have to be "reconstructed" in order to be viewed or manipulated. Of the five image resolutions available, we chose the Base resolution image size (512 x 768 pixels) for the World Wide Web images. It delivers fine image quality for on-screen viewing, and still has a reasonably small file size (about 1.2 MB)-- even smaller when compressed with JPEG (80-200 K). We wanted a balance between image quality and transmission performance.
We used the KODAK Photo CD Acquire Module in conjunction with ADOBE PHOTOSHOP software to access the base resolution images. From within the PHOTOSHOP software application, users can "acquire" an image from a Photo CD. There are other tools that can accomplish the same thing, but in this case the Acquire Module offered two advantages:
A further description of tools and techniques for acquiring images from Photo CD is available.
Using PHOTOSHOP software tools, we cropped each image to clean up the edges. Photo CD scans often have a small border of non-image area around the image itself-- part of the slide mount, or negative-- that gets included in the scan along with the image.
We "spotted out" any dust contained in the image (the PIW scanner will scan dust as well as pictures!) with the "rubber stamp" tool. We made minimal adjustments to the other image attributes, knowing that the end results would be displayed on a variety of monitors and systems. The adjustments included contrast, brightness, color, and sharpness via Photoshop's "Unsharp Masking" filter. We saved the final result in RGB as a 24bit TIFF file (millions of colors), and compressed the file using JPEG.
JPEG compression offers a variety of setting choices, with the least compression offering the best image quality retention. As greater amounts of compression are applied, the resulting images begin to degrade-- for the most part unnoticeable until the image is carefully inspected or enlarged.
We chose JPEG compression settings to deliver the best balance between image quality and speed of transmission. They varied by image, but were all near the "medium" range of JPEG compression. Our 1.2 MB files compressed down to between 80 and 200 kB.
If you are intending to do image manipulations on any of the Kodak images in our offering, we suggest that you download the complete Photo CD Image Pac file. It takes quite a bit longer, but offers the advantage of higher resolution versions of the image. Images "reconstructed" from the Image Pac file are well suited to further image processing.
See Image Pac Compression and JPEG Compression Compared for a summary of differences between the two approaches to efficient compression of image data.
The index print approach delivers a selection of choices on a single screen, providing a fast, visual way to choose which images to view in the higher resolution. Each thumbnail is 82 x 123 pixels-- resized from the same Base level image file that is delivered as JPEG compressed. Using ADOBE PHOTOSHOP Software, we "pasted" the thumbnails into an index print to give you an image editor's view, and added numbers to each picture.
We converted the index print from RGB (millions of colors) to indexed color, using a color table limited to 50 colors. This self imposed limit results in good and bad effects:
Each image in the series is available as a KODAK Photo CD IMAGE PAC file. We copied the Image Pac files from the Photo CD to our FTP server (they are contained in a directory on the Photo CD Master Disc called "/PHOTO_CD/IMAGES/." If you would like to download an IMAGE PAC file, (it's worth the wait!) plan to have a sandwich while you're waiting. Sorry, sandwiches are not available by FTP. :-)
If you are a Macintosh computer user, PLEASE READ ME before downloading Image Pac files!
Monitor settings and ambient viewing conditions are the biggest factors in display quality. Control your viewing conditions by viewing your monitor in a dimmed room. Avoid light falling directly on the monitor (it lowers contrast).
Optimize the monitor by setting the following: