Managing Large Format Drawings

Original Drawing Size
Usually measured in inches or centimeters. Common paper sizes have been designated by a letter.
See Wikipedia Paper Size entry or printhandbook.com chart.

Scanned Image Size
is measured in pixels (dots).

This is related to, but not the same as image resolution. 300 dots per inch (dpi) refers to the number of pixels (dots) captured per inch of the original object scanned or when displayed or printed. This can be changed while editing the image, so it may or not be an accurate measure of the original object. Digital photo dpi impacts print size and quality, but does not relate to the size of the original object photographed. Photographers often place an object of known size next to an object they want to be able to calculate the size of.

Maximum Pixels Supported
Each file format and image viewing/editing program has maximums that are supported. There may also be limits based on the RAM or disk space available. Older versions often supported a lower maximum. Because of this, there is no "best" format for compatibility and standardized storage of oversize image files. You should test in the environments they will be used and retest when environments change. With enough RAM, Irfanview will open larger tiff images than Photoshop.

Image Viewing/Editing Programs File Formats

Photoshop: 300,000 by 300,000 pixels per image (Max: 600dpi=500"; 400dpi=750"; 300dpi=1000"; 200dpi=1500")
Photoshop has a much lower max when opening tif images compressed using CCITT (Fax - bitonal) or JPG. Use Irfanview to convert to LZW tif.

JPEG 65535×65535 pixels (Max: 400dpi=163"; 300dpi=218"; 200dpi=327"; 150dpi=439"). Photoshop only supports ~30000 pixels: 150dpi=200"
Photoshop Elements: 30,000 pixels by 30,000 pixels TIFF maximuim file size 4GB
Irfanview: determined by RAM (turn off undo and restart computer to maximize RAM) PDF
SmartWorks Pro (Colortrac Scanning Software): seems to handle ~1333.33 MPixels before it stops. Might be dependent on RAM as well?  

Disk File Size
The disk space needed to store the image is determined by the file format and compression (many file formats allow multiple compression options). Some compression formats are not fully supported by all image viewing/editing programs..Because of compression, file size can vary greatly, but the image must be uncompressed to view or edit. A highly compressed image may take a long time to load, view or edit even though its file size is small. Image editing programs often require that an image be in grayscale or RGB format to edit, even if the original file format was bitonal or indexed color. Warning: Older computers, peripherals, operating systems, file formats (such as Photoshop .psb) and disk formats (such as FAT32), do not support large file sizes (over 2GB). They also may not support large disk drives (>2TB).

Large Format Scanners:

  • Colortrac SmartLF SC25. I purchased this scanner in 2013 from GEIWideFormat. This is one of the few large format (25" width) scanners that can be easily transported by one person. Optional SmartWorks Pro software necessary to manually set scanner parameters - I don't recommend this scanner with the bundled SmartWorks EZ Touch software. Tips: There are sometimes small lines/artifacts in the scan which are acceptable for drawings but not photos. Regular cleaning can help this.WD-40 cleans and reconditions the feed rollers as well as lubricates the mechanism. Rain-X can be used to protect the scanner glass and fill in tiny scratches. Use the scanner's magnetic guide to keep long documents straight. A purchased magnet can be used as a second guide on the left side of the document. For long documents (such as track charts) that are narrower than the space between the paper sensors, you can create a paper strip that can inserted under the sensor to fool the scanner. Just remove the strip or hit the stop button when the actual document has gone through the scanner.
  • KIP3100. Purchased by the PRRT&HS mostly for its printing capabilities. They did not purchase the added cost key to unlock color scanning so all scanning must be done in bitonal or dithered gray scale modes. Because of this, only high contrast originals can be easily scanned. It sometimes requires experimentation to get the right scan settings for a particular document. Biggest problem we have had is scratches on the scanner glass, evidently caused by the raised ink on some linens. There are four separate scanner glass sections, costing $250 @ to replace.
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