Message-Id: <mailto:199412082206.QAA29498@library.wustl.edu> Date: Thu, 8 Dec 1994 13:42:27 -0800 From: Robert MacKimmie <mailto:rm@CALIFHISTSOC.ORG> Subject: Re: UNM Hlth Sci Cntr Imaging Project To: Multiple recipients of list IMAGELIB
Begin forwarded message:>>>Date: Thu, 8 Dec 1994 13:03:24 -0700
>>>From: Lisa kindrick <mailto:lkindric@BIBLIO.UNM.EDU>
>>>Subject: UNM Hlth Sci Cntr Imaging Project
>>>The University of New Mexico Health Sciences Center <munch...>
>>>Currently, our plans are to create a master TIFF image at 600 dpi,
and then to link a TIFF image at a lower resolution, possibly 300 dpi, to the record in the online catalog for viewing. >>>what compression scheme should we use?
>>>scan at a lower resolution than 300 dpi for viewing
600 dpi is good for the archival version and should be saved in a "lossless" form of compression such as LZW. They can be stored on optical, DAT, or whatever is affordable/archivally sound for xyz years--depends on planned strategy. [We are storing to optical, collecting enough opticals and then bumping two gigabytes at a time to DAT. DAT storage is planned for just a few years until more massive and stable storage is affordably available.]
Before it is stored to optical, we use the 600 dpi version to do a "Save As" at a lower (screen) resolution. This can generally be 72 dpi unless someone is going to magnify the view to see the detail. If someone will magnify 2X, then save it as 144 dpi. This commonly occurs with maps or detailed scenes. If 4X is anticipated, save at appropriate dpi. If anyone has waited for a 600 dpi image to open even on a fast machine, you will know why it is best to have as low a resolution image as is possible online. Many machines do not have the CPU or memory to handle larger images. Some OS platforms cannot readily open some versions of JPEG (there are many). Some machines implode if asked to handle too large an image. Smaller (file size) is always better for widespread public distribution (Internet).
>>>store the images on an optical disk system and to eventually make
them available over the Internet as part of our online catalog.
Allowing anyone to transmit a 600 dpi image over internet would bring down the Internet in no time. This is the reason for screen resolution only (72 dpi) with the additional possibility of reducing the size to 4x5 inches to make them even smaller. Here the game plan would need to be evaluated as to whether one is making the image available for access, browse and identification --- or for major other applications where you might send an optical cartridge instead.
Much of what I describe comes from the practical experience of implementing a digital imaging project over the last three years. It works! Thinking out the details of a practical working methodology will save major headaches later.
>>>viewing TIFF and GIF files under the OSF/1
Someone?
(Sorry if this is common knowledge for some.)
Robert MacKimmie Curatorial Director of Photography California Historical Society, San Francisco mailto:RM@califhistsoc.org