The average file size is approximately 36.5 megabytes for 7x9 inch photos and 47.5 megabytes for 9x9 inch photos. They were scanned at 750dpi on a Crosfield Drum scanner. These are the original uncompresed files. This format is a full resolution file format with the following file extension. These files should open in most browsers as they are an open source file format. The average file size is approximately 7.25 megabytes for 7x9 inch photos and 9.25 megabytes for 9x9 inch photos. The original TIFF format files were compressed using Adobe Photoshop CS4 and their Quality setting was set to 10. This format is a compressed file with the following file extension. Adjacent aerial photographs can be used for stereoscopic viewing in most areas of the state (except portions of Carroll, Piatt and Stephenson Counties). The individual aerial photographs distributed here have not been georeferenced.
#Aerial photo archive#
Access to these print collections is becoming increasingly restricted.ĭigitization, or print scanning, has been completed for statewide coverage of Illinois in an effort to create a lasting archive of this irreplaceable collection. Use of the paper prints over time has resulted in their becoming faded, worn, defaced, or lost. Due to this fact the original photographic prints are now the best substitute for the negatives. An attempt to copy the negatives prior to their destruction resulted in a very poor quality replacement. The original silver nitrate film negatives were purposefully destroyed by the National Archives in the early 1980s due to deterioration and instability. This collection history gives details about the approximately 33,500 photographic paper prints that were scanned. Statewide aerial photographs were first acquired for Illinois from 1937 through 1947.
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