Message-Id: <mailto:199507251909.OAA28855@library.wustl.edu> Date: Tue, 25 Jul 1995 15:06:39 +0400 From: Terry Lund <mailto:lund@PCD.KODAK.COM> Subject: Re: Advice requested for scanning to PhotoCD To: Multiple recipients of list IMAGELIB
Mia,You might want to check out the sample digital image area on Kodak's web server. The page at:
http://www.kodak.com/digitalImages/samples/aboutPix.shtml
describes how we started with Photo CD images and generated the sample images shown in that section of the Kodak Web Server. This doesn't address your questions directly, but does illustrate what can be done starting with Photo CD images. I added other comments to your individual questions, and I hope this helps.
-Terry Lund
At 10:52 AM 7/25/95, Mia Massicotte wrote:
>We have had a professional photographer take some shots of our library for
>a virtual tour project that I'm putting together. I want him to put the
>images on a PhotoCD, which I will later manipulate on a Mac with
>Photoshop, and mount them on our Mac webserver. I would like one high
>quality archival image for posterity, one image at 72 dpi for the
>webserver and subsequent screen viewing, and one thumbnail.
>
>
>My questions are:
>
>1a. For the image at 72 dpi, I don't want to have to resize or crop these
>images when I place them into my web pages. I think l want the images to
>be approx 4" h x 5 inches wide when displayed on a monitor. I've been told
>I need to specify to the lab that something called the 'aspect ratio'
>should be 4x5 for 35 mm film. This should result in an on-screen image of
>300 w by 200 h pixels. Is my information correct?
Assuming you are scanning from 35mm film, the original film image is about 24mm by 36 mm size (aspect ratio is 1 to 1.5). This means you cannot get an image 4" by 5" (aspect ratio is 1 to 1.2) without introducing distortion in one direction or the other. You can have 4" by 6" or you can have 2.5" by 5" by interpolating the image data.
Photo CD images have five resolutions "built-in", for scanns from 35mm film. The resolution called BASE/4 will be 240 by 320 pixels, which is pretty close to what you wanted.
>
>1b. If I want the 72 dpi images instead to display on screen (without
>cropping) at a size of say, 3" high by 4" wide, how should I specify this
>to the lab making the CD?
>From the above comment, the BASE/4 image will be 3.33" by 4.44" at 72 dpi
on a monitor.>
>2. For the 72 dpi image, I assume that the image would be in PICT format
>on the CD. If I then convert the 72 dpi image to jpeg for my web project,
>will this result in too great a loss of quality? Should I try to convert
>the archival image to a 72 dpi jpeg instead? Any suggestions?
No, the image is not in PICT format on the Photo CD disk. Follow the notes from the Kodak web page referenced above to see how we converted from Photo CD files directly to GIF or JPEG for the web.
>
>3. Initially, I used Apple's QuickTake digital camera for some quick and
>dirty prototyping. I noticed that displaying the photos (I had converted
>from pict to gif for the test) on Mac monitors (475's, 575's, Powermacs)
>looked acceptable; but on PC monitors were way too dark. Is this darkness
>a function of the PC monitor's capability, or did it have more to do with
>the gif compression? Will I run into a similar problem with my jpeg
>images, and if so, can it be avoided?
This gets complicated (and can be messy) because monitors can be setup to almost any set of conditions, and the viewing conditions also impact the apparent darkness of images displayed on different systems. The only way to be sure of the results is to have some type of color management software running on the different computers, and to have the viewing conditions controlled (limit the amount of stray lite on the screen, and have somewhat subdued lighting).
>
>The bottom line is that I want the highest quality image that I can get
>from the original, to mount on my Mac webserver, for monitor display at 72
>dpi, with an on-screen size of about 300 pixels wide by 200 pixels high.
When you start with digital capture (as in #3 above), you have to worry about the camera color calibration, as well as any of the processing software formatting the images, as well as color management for the browers displaying the images. At least if you start with Photo CD images, you have image data that is in a well defined color space.
Terry Lund Phone: 716-588-6855 R&D Mktg Liaison FAX: 716-477-1498 Mail: 7/83/RL/02210 KNET/KMX: 258-6855