Central Pacific Railroad Photographic History Museum

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© 2014 CPRR.org. Use of this Web site constitutes acceptance of the User Agreement which permits personal use web viewing only; no copying; arbitration; no warranty.
Technical Notes

Stereoscope
Stereoscope (H. Ernemann).  Courtesy Bogdan Stroescu.

Freeviewing (seeing the image in 3D without a stereoscope) with a large monitor.
Once you have learned to freeview, it's easy to freeview a 2x stereoview (as shown in the Exhibit and Photo-Gallery on our website) on a large monitor.  The trick is to view from about 4 feet away and to use a distance prescription, not reading glasses.  (Easy to focus when looking above the line of bifocals, difficult when looking through the lower reading portion.)
For an explanation of how to freeview, click here.
How to See Stereo (Relaxed viewing), click here.
If you are unable to freeview, an unmagnified Folding prism stereoscope suitable for viewing stereoviews displayed on a computer has been invented by Monte Jerome Ramstad.

Compatibility Testing.
We have tested this website with Netscape Communicator/Mozilla, Microsoft Internet Explorer, and Safari and are not aware of any incompatibilities. Website Garage reports Excellent Broswer Compatibility and HTML code check.  Please let us know if you experience any problems.

Browser Bug does not display wide images properly
One popular browser does not correctly display wide high resolution maps, diagrams, and panoramic images, etc., cutting off the right side of the image which is not displayed; Another browser gets the shape of large images wrong, or pretends that the picture is missing.  There is nothing at all wrong with the pictures.  If the spectacular Alfred A. Hart Map of "THE BURLINGTON ROUTE" is missing the word "ROUTE" in large green letters on the top right, or if large images appear squeezed in one direction, you have one of these defective browsers, and should complain to the software company about the problem and choose another web brower that works correctly to view such wide images.

"I had a life once ... now I have a computer and a modem." Rafey

Browser Bug clicking a link stops download
Many of the pages at the CPRR Museum are designed so that you can enjoy viewing the top of the page while the rest of the page (including large pictures) downloads so that the rest of the page will be ready in time as you scroll down the page. However, some browsers stop downloading a page and its images whenever you click on a link. That makes complete sense if the link is to another page that will be displayed in the same window, but is incorrect behavior if the link is to another place on the same page, or to another page that will display in a separate, new window. Consequently, if your browser has this problem, you may need to take care to wait until each page finishes downloading before clicking on a link, if you want to avoid interrupting that page's downloading. If you click on a link prematurely and find that as a result, pictures are missing or only partly displayed, or the bottom of the page is missing, hit the reload button to fix the problem. (If images still fail to fully load following a refresh, it may be necessary to clear your browser's cache, and/or quit and restart the browser, before trying to load the page again.)

Changing Text Size. Large Type Edition. [Courtesy ©ASNR.org]
TIP FOR BETTER WEB BROWSING:
Large Type Edition
To reduce eye strain when reading articles online, increase the font size for your browser.
In most browsers you can accomplish this with a trip to the "View" menu. Look for something called "Text Zoom," "Text Size," "Increase Font," "Make Text Bigger" or similar. Courtesy ASNR.
More web browser tips.

Universal Access for the visually impaired can also be assisted by software that enlarges the screen image. We also provide catalogs with text captions describing the transcontinental railroad images.

"I don't have any meetings today. I'll just fool around with my computer's settings until it doesn't work." Dilbert cartoon

Download Speed.
The CPRR.org website was designed to show the wonderful Central Pacific Railroad images with reasonably fast load times while not sacrificing image quality.  Page load times from the Internet have been measured at times of low congestion, confirming that the homepage loaded and displayed in less than 20 seconds, and pages with large individual images generally loaded and displayed in under 5 seconds using a cable modem or DSL.  This testing was done using Netscape Communicator 4.76 and Internet Explorer 5.0 running on a 5 year old slow Power Macintosh 7200/75 using Mac OS 8.6 and 9.0.4 with a SURFboard external cable modem also also with an ADSL gateway attached to the computer by ethernet connection. (Since this testing was done several years ago, broadband speeds have significantly increased.)  Surprisingly, these measured Internet page load times from a server 1000 miles away were found not to be significantly different from load times directly from our hard drive using the local disk copy of the website on our computer.  We have also tested with dial-up connections and regret if Internet congestion or a dial-up modem connection make your viewing unpleasantly slow.  Hopefully, an inexpensive high speed internet connection ($29.95-$49.95/month) will also be available to you in the near future – you should definitely take advantage, if available!  A March, 2004 Nielsen/NetRatings study found that 42% of home users and 77% of business users had high speed broadband connections. If browsers were properly designed to download images that are visible in the window ahead of off-screen images that will not be immediately visible, images would appear on screen dramatically faster.  This website is hosted by ValueWeb.  If you have a cable or DSL high speed connection that is sluggish, you possibly need to properly tune your Windows or Macintosh system and may see a dramatic speedup, since the default networking parameters may not be correctly set for high speed Internet connections.

System requirements for eBook viewing.
This website contains a number of electronic books in pdf ("portable document format") which require pdf viewing software to view. The entire book is contained in one very large file (tens of megabytes in size), so you'll need a high speed internet connection, and a fast computer with lots of memory or viewing may be very slow. (The big advantage of this format is that you can search the page images using the "find" command.)

Dual 19" Monitor viewing.
The Photo-Gallery and Exhibit are best viewed with the index page on the left monitor and the enlarged stereoviews in a separate window on the right monitor (each monitor 1024 x 768 pixels).  Clicking on a small image on the index page automatically opens a second window with the magnified image [close the extra windows when done].  Having two large monitors is a delight for Internet browsing and has recently become quite affordable.  Having two 19" monitors is highly recommended, second only to a high speed connection, such as by cable modem or telephone DSL.

"A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools." —Douglas Adams

Color Scheme.
The black text on a red or yellow background appearance used on the CPRR.org website was chosen to approximate the most common colors used by the 19th century photographers (Watkins and Hart, respectively) when mounting CPRR stereographs.  Sometimes a page will provide its owns colors and background which you can override by setting your own preferred browser colors if you don't like our choices or if you find pages difficult to read, for example, due to color blindness.  In Netscape Communicator set the Appearance/Color preferences to the text and background colors that you can see best and check the box to "always use my colors, overriding page."  In Internet Explorer set the Web Browser/Web Content preferences to the Page & Links colors that you want for the text and background and uncheck the Page Content option to "allow page to specify colors."  (Various versions of browsers may have these preferences set slightly differently, so look around to find them if color preferences are not edited exactly as described here.) Also, you can easily change the red background of the Home page or the blue background of the Exhibits page to suit your taste – see the background color choices near the top of the page, and click on your preference.

Monitor Calibration Grayscale

Grayscale for Monitor Calibration.
The appearance of the images displayed on the CPRR Museum website "can be greatly affected by the  brightness and contrast settings on your monitor.  If the images appear too dark please make sure that you can distinguish each percentage bar.  For instance, the 40% and 50% bars are clearly distinguishable and so should the 90% and 100% bars.  If they appear to blend together then adjusting your brightness and contrast settings should make them distinguishable."  You can also verify the color and contrast settings. Grayscale Courtesy of an Anonymous Donor; reproduced by permission.

"On two occasions I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question." Charles Babbage, "Father of Computing"

Optical Character Recognition.
Many of the readings were automatically converted from scanned or digitally photographed19th century original documents by means of Optical Character Recognition (OCR) software.  This allows us to have many more 19th century documents on this website than we would have room to include without doing this conversion.  Whenever we have found images of the original text pages available on-line, as is now often the case with 19th century magazine articles, we have also included links with the article, to allow you to view the original.  While the accuracy of OCR has greatly improved, particularly when the text is very distinct, it still has significant limitations, especially when the original is imperfect, and when dealing with formatted text, difficult typefaces, tables and superscripts.  As a result we must give you a very strong WARNING:  DO NOT RELY ON OCR CONVERTED TEXT.  These OCR converted documents are very useful for casual reading and searching with your browser's find command, or our website search capability, but you must examine the original documents if accuracy matters.  Never rely upon a date, number, formula, or other detailed information without first checking its accuracy, as the OCR software often inserts errors which are not the sort of mistake a human would make or easily recognize.  We have corrected many such errors, but undoubtedly numerous others remain, and our limited resources prevent us from fully verifying all the text.  We have also chosen to make available converted documents before the formatting and limited proofreading is completed.  If you identify any errors, let us know.  If you would like to volunteer to proofread one or more documents and let us know about errors that need to be corrected, we would be most appreciative if you don't have access to the original document, contact CPRR.org to see if we are able to fax you a copy for proofreading. In some cases, we display page images on html webpages and hide the imperfect OCR text in a tiny font at the bottom of the webpage, with the text almost the same color as the page background, to allow search engines to index the page. Sometimes we include the entire text of an article on a webpage above an image of the first of several page images, with subsequent page images on following webpages. In other cases, a complete book or document may be presented online as all page images in a pdf format file with OCR text under the page images, so that you can see the original, but the text can be searched using your pdf viewer's find command, and can be indexed by search engines. The various presentation formats have been used to accomodate varying degrees of quality of the original copy, success in OCR, whether the resources have been available at the time to do extensive proofreading and manual corrections, and as the scanner and OCR software have changed or improved over time.
[Some common OCR errors: (l > d ; lie >he ; ),on > you ; Dot > not ; tip > up ; 1 > I ; oil > on ; tile > the ; bad > had ; yon > you .]

How to avoid illegible black lettering on a red background (Watkins and Houseworth views).
To avoid severe smearing of the black lettering on red cards when saving jpeg images, it is essential to enable the optional (4:4:4) Sub Format.  (This option is available in the Photo-Paint component of Corel Draw 8:  144 dpi 2x magnification, JPEG Enhancement- 14% compression, 0% smoothing, Optimized Encoding with Optional (4:4:4) Sub Format used for red cards.)  This is not necessary for Hart's yellow cards, as Photoshop's default medium jpeg images do not show smeared black lettering on a yellow background, as they do with black lettering on a red background (Adobe Photoshop LE 3.0:  144 dpi 2x magnification, JPEG medium used for yellow and other color cards, except red).  Alternatively, 8-bit gif images of red cards are excellent, lacking this smearing problem, but are about 80% larger (less efficiently compressed) than the (4:4:4) Sub Format jpeg images.

How can unacceptably discolored or unevenly colored sepia images be corrected?

Corrected discoloration (recolorized monochrome)
Only the left half of this stereograph has had its discoloration corrected.
Using Adobe Photoshop, we have observed that adjusting contrast, and burning or dodging can cause unexpected and unpleasant color shifts but we realized that this problem could not occur in monochrome.  We found that this insight could be applied to restoring badly discolored or unevenly colored "black and white" sepia images.  An RGB scan of a badly discolored sepia image can be restored to a uniform sepia color by first converting to monochrome, then converting back to RGB color and adjusting the color balance to any desired sepia (about +100 red/cyan, +11 green/magenta, and in the range of -12 to -39 blue/yellow).  While the image is monochrome, the dodging tool can also be used to remove stains or foxing, for example, in the sky, that would otherwise result in an unacceptable discoloration if dodging were attempted in color. (No dodging was done in the above example.)  The cause of this discoloration is discussed on the Frequently Asked Questions page.

"There are 10 kinds of people in the world, those who understand binary, and those who don't." —anonymous

How to avoid reflections and slightly off color interference patterns when scanning images.
Take the stereographs out of their Mylar plastic sleeves when scanning to avoid light reflections off slight curves in the shiny Mylar and also to avoid "Newton's rings," the slightly colored interference fringes resulting from the very close distance separating the plastic sleeve from the glass surface the stereograph is resting upon when in the scanner.  (But make sure that the scanner's glass is clean before allowing the photograph to come in contact and use photo gloves when handling the stereographs.)

How to avoid moiré patterns when scanning engravings.
Scan at the highest available resolution in full color (600 dpi).  Shannon's sampling theorem requires the scan to be at twice the highest spatial frequency in the engraving to avoid aliasing.  Then resample the image to the desired reduced screen resolution (72 dpi), which eliminates the high frequencies by averaging pixels, so that the annoying wavy patterns are avoided.

"There's no place like 127.0.0.1!!!" — robpoe

How to scan large maps or blueprints using a standard small format scanner.
The Maps page includes scans of some large format maps which we were able to include without having an expensive large format scanner available. The simple trick is to use a blueprint duplication photocopier (which is a common service at specialized copy centers) to make a reduced size photocopy. We found that two size reductions resulted in an 8 1/2" x 11" high resolution copy that could be scanned using a readily available page size scanner. Two examples of using this method are the California and Nevada survey maps. The quality of photocopies is considerably less than that of original continous tone or color maps, so we would not recommend this method when original maps are available, but when only large format blueprints or photocopies are available or when the original is line art, there is little loss of image quality from the additional size reduction copying steps as the large format photocopiers used by architects and engineers are of extremely high quality. Although time consuming, alternatively, it is also feasible to scan a large format original in sections which are then carefully aligned and put back together using Photoshop. An example is the Sierra Summit contour map which was reassembled from two scans.

Is Internet display of high resolution stereograph images currently possible?
Not with the entire image being visible at one time.  Stereoviews consist of a pair of images, each about 3 1/2" in size.  The 19th century views shown on this website are of small albumen prints which themselves are not capable of high resolution.  When we speak of "high resolution" what we actually mean is that the digital image does not further degrade the resolution.  To do this 600 dots per inch (dpi) scans of the original stereoview are marginal, and 1200-2400 dpi would actually be required to capture the full available resolution of the original stereoview.  Due to equipment limitations we have reluctantly compromised on 600 dpi which may be acceptable because much of the detail being lost is the appearance of the emulsion itself rather than useful photographic image information. (Albumen prints have a fine pattern of cracks in the emulsion which cannot be seen on 600 dpi scans but could result in aliasing artifacts.)  With improved scanners, faster computers with more memory, larger disk drives and recordable media, and improved image compression methods we hope to find it practical to scan stereoviews at 1,200 dpi in the near future.  However it is not possible to display even a 2,100 x 4,200 pixel, 600 dpi stereograph scan in its entirely on the 72-95 dpi CRT monitors or flat pannel displays currently used for computers now available for Internet browsing.  To have a 600 dpi image fit on the screen, the display resolution would need to be increased by a factor of 4 to about 300 dpi (which is true medium resolution such as seen with low cost consumer printers; quality printers use a minimum 1,200 dpi on the paper or much higher for commercial printing) and because images are two dimensional, a broadband connection, computer, and graphic display system 16 times faster than currently available would be required to keep download and display times similar to those currently experienced.  These will probably not start to be in common use until at least 2005-2010 or later.  An improvement of 256 times would be needed to display high resolution 1,200 dpi stereoview scans, which will not be possible anytime soon.

How does the "wobble stereo" 3D animation on the homepage work?
The example of animation on the homepage and the stereo exhibit, inspired by Miklos Legrady's work, uses a simple javascript to swap a correct stereoview with a Photoshop created pseudoscopic version of the same view under the full control of the user.  (In a pseudoscopic view, the left and right stereo images have been interchanged.)  Legrady uses a continuously animated single image (half a stereoview), but we thought it would be interesting to show the animation with the entire stereoview.  Changing an image when you point to it is a standard browser effect ("javascript rollover").  Thus, moving the cursor back and forth across the picture's edge causes the animation whenever and as fast as the viewer wants, and avoids visual discomfort.  This simple trick which gives the user control of the animation might have wide appeal, as it is unobtrusive when not being deliberately invoked. To achieve the appearance of rotation, the two images are aligned so the nearest object is in the same place.

Copy Protection.
If you would like to use images from the CPRR Museum on your website, see this FAQ.  This website depends for its existence and continued availablity on the good will and support of donors willing to allow their valuable images to be displayed on-line.  We hope that allowing personal educational viewing at the CPRR Museum website at no charge, while charging a use fee for copying is a good compromise, but when images are taken without permission, it puts our entire project in jeopardy.  Pages on this website are designed to help prevent unauthorised downloading of images and breach of both copyright and the User Agreement.  We have tried to do this in unobtrusive ways that don't impair the quality of your experience at the CPRR Museum.  We regret that copy protection has become necessary, but it was put in place only after repeated pirating of content from the CPRR Museum website.  For example, an institution took our entire website, removed the copyright notice from our homepage and republished a seriously obsolete version of the CPRR Museum on their webserver with the files jumbled so badly that most of the links were broken, and then they distributed the broken pirated copy of our work to other institutions on compact disk, thereby damaging our reputation.  In another case, a foundation hosted a website that copied about 50 of our most spectacular images without permission.  In yet another instance, a donated rare photograph that was a treasured family heirloom was copied and placed on another website without credit, while falsely claiming that it was theirs.  (Their webmaster became irate when at the request of our very upset donor we politely asked them to please link to our page instead.)  ...  While it may be possible to circumvent technical copy protection mechanisms, please don't do this both because ripping off the pictures isn't a nice way to repay our donors for their generosity in supporting this project, and also because doing so was recently made a serious Federal crime under the Digital Millenium Copyright Act.  Instead, please ask for permission.

We would be delighted to hear your design suggestions    How can we improve this website?
we've been wrestling with a number of technical issues (as noted above and on our FAQ's page):
We've tried to keep the design of this website simple without frames or Java programming while maximizing the area available for images, given the limited resolution of CRT's.  Here are some issues that we're aware of but haven't found entirely satisfactory solutions for:

When making suggestions, please try to be very clear and specific as to what software and parameter values you are recommending, so that we are able to duplicate your results.  We listen carefully, greatly appreciate your help in improving this website, and have experimented with every suggested website improvement that gave us the detailed information we needed to give it a try.

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