Viewing

Tips for Improving Image Viewing Quality


Extreme care went into scanning and adjusting the images included in this exhibit so that they would represent as accurately as possible the original coins. In order for you to obtain the best possible results, we have outlined several things you can do to improve the way the images appear on your computer, along with the technical specifications that we used:

Optical illusions on conventional curved monitor screens

Major problem: left image looks oval or "bent" - Most notably on some 13" curved screens the coin images will look "bent" or convex. This is due to incorrect proportions (height to width) of the display screen. Fortunately, this is easily remedied as the proportions of the display screen can be controlled. On older monitors there are knobs on the back of the monitor that turn to adjust screen heighth and width. On newer monitors the adjustments are made from knobs or push buttons on the front of the monitor (sometimes hiden by a cover much like TV controls). This problem cannot be remedied by simply reducing the size of your internet browser (i.e. using the mouse to bring in the borders and thus reducing the size of the netscape or microsoft window). This is a proportional problem not a size problem. Usually a slight downward (or in some cases upward) adjustment of the display screen width or height to the point where the coins appears round will resolve the problem and will give a more accurately proportioned image for anything you view on the net.

Minor problem: slight difference in image size - On some screens the left image (coin obverse) will look slightly larger that the right image (coin reverse). This is a minor problem that many individuals may not even notice. Actually, the images are the same size, the illusion is due to the curvature of the viewing screen. If you have what is known as a "flat screen" the images will look quite close in size. For those with conventional screens this optical illusion can be lessened, if you wish, by narrowing your internet browser screen (using your mouse) and moving it to the center of the monitor. The distortion will proportionally lessen the closer the two images are to the center of the monitor.



Objective color adjustments

The most basic problem in viewing images is determining the quality of the image when trying to make adjustments for various monitor and software problems. How can one know what adjustments to make when one has never seen the object that was scanned and thus does not know the true colors, brightness or other parameters?

As an objective test we have included a scan of Kodak color control patch strip from a "Kodak Color Separation Guide and Gray Scale (Small)" Q 13, catalog number 152 7654. This is photographer's color bar. All color bars should be fairly close in color, brightness and contrast thus, by comparing a color bar available at a local photographer's store with the image of the color bar presented here one can make adjustments with a certain degree of objectivity. It is best to lay the color bar on a table to the side of the monitor when making the comparison as there is excessive light reflected from the monitor when the sample is placed directly on the screen. We would like you to see the true quality of the coin images in this project. If the color bar comparison reveals a problem see the following section.
Color bar at 100 dpi (39K)   or   Color bar at 200 dpi (172K).

The images displayed in this exhibit were made using an AppleVision 1710 monitor that was recalibrated every two weeks. Color was set at a 1.8 Gamma curve, with a white point of 9300 + 8MPCD and using ambient light adjustments. The color depth was set at millions of colors with a resolution of 832 x 624, 75Hz with mid level brightness and high contrast.



Optimal screen/monitor settings

Viewing images is best done using the factory set monitor gamma setting with medium brightness and higher contrast. These parameters were adopted because many monitors are set this way at the factory and in my experience individuals rarely adjust the settings. Unfortunately, there are no standard monitor settings, hence if the images look too dark or too light, try making the following adjustments:

Monitor controls typically located on the front of the monitor:
Monitor controls typically located in a control panel (the "panel" is part of your system software):
Other viewing tips:

Viewing the 250 and 500 dpi images

These images will appear by clicking the appropriate dpi number (dots per inch) to the left of the small image. I use dpi as I found it was the most commonly understood abbreviation, technically when viewing a image on a screen the correct phrase is ppi (pixels per inch) while dots is the measure for printed images. Since the image area is squared the 500 dpi image is four times as large as the 250 dpi image; therefore if you have a slow modem the 250 dpi image will appear much faster.

Many individuals will have their computer set so the larger JPEG images will be launched through their web browser. The result is that the larger image will appear on a separate page. This is probably the least desirable way to view the images, for several reasons. In this mode one cannot simultaneously view the image and the text page; additonally, the image is not sized to the screen, image manipulation is not possible and further, one is limited to viewing only a single image at a time. Various image viewing applications are available as freeware, shareware or at minimal cost which will allow you to bring up several images at once (presuming you have sufficient RAM memory) and some have "crop and zoom" features that allow you to magnify image selections. Here are some suggestions for Mac and PC users:

Macintosh Users

A popular freeware image viewing utility for Mac users is JPEGView 3.3. You can download this free program from most info-mac ftp sites including the one linked here (this is a link to the info-mac ftp mirror site at Apple Computer. The file will download as a compressed BinHex archive which will need to be decompressed using a Stuffit Expander or a similar decompression utility.)

JPEGView works as a helper application for your web browser and includes a handy "crop and zoom" feature. To enable it to automatically open the 500dpi and 250dpi images you will find for each coin displayed in our exhibit, you will need to tell your browser to launch JPEGView for viewing .jpeg or .jpg images. For Netscape 3.0 users, this can be done by going to the "general preferences settings" under the "options" menu and "browsing" for the location. Click the "helpers" tab, then highlight the "jpeg" choice in the window, then click edit to locate JPEGView on your hard disk. If you are using a different version of Netscape or Microsoft explorer, consult your browser help files to learn how to enable helper applications.

PC Users

There is no dominant image viewing software in the PC world, but many like using LView. A shareware version of the LViewPro application for Windows 95 and NT users may be obtained from www.download.com by clicking here.

PC Magazine recently included a review of other graphic file viewers. In addition, PC Computing has put information about some of the more popular viewers into a convenient table; several products can be downloaded directly from this page.


Scanning specifications

The scans were created from the original coins rather than photographs using a Hewlett Packard ScanJet 4c. The software was Deskscan II 2.3 set at millions of colors at 600 dpi (reduced to 500, 250 and 100 for the images used on the web) and scaled at 100% (brightness and contrast differed depending whether the coin was copper, silver or gold). Images were then corrected in Adobe Photoshop (3.0.5, later 4.0) with the coin as a guide. Excess border space was cropped off to reduce the file size then each image was saved as a jpeg at maximum quality (numerically 8, in Photoshop 4.0). We use jpeg because of the quality and compression ratio. Typically, uncompressed coin images at 500 dpi are in the 900 to 1000K range; by saving the images in jpeg we get between a 7:1 and a 10:1 compression ratio (usually within 100-200K).



For questions or comments contact Louis Jordan by:
E-Mail
, telephone: (574) 631-0290, or mail:
Department of Special Collections, 102 Hesburgh Library,
University of Notre Dame, Notre Dame, IN 46556