I am doing historical research for which the only document source is microfilm typically created in the 1950s by technicians who did not understand the characteristics of this then new technology. Flat-bed scanning was not available at the time and even flourescent illumination was rare so the resulting images suffer from vignetting both as a result of the camera system, which used an inappropriate f-stop, and the illumination from incandescent spot-lights. This is further aggravated by the most common implementations of microfilm viewers in libraries, which use a lens to focus an image on a camera sensor instead of scanning the microfilm. The resultant image files thus have several layers of vignetting and optical distortion. And there are, of course literally millions of reels of microfilm, each with typically over 1000 images. The Family History Library of the Church of Latter Day Saints has fortunately done flat-scans of the several hundred million microfilm reels they have buried under a mountain in Utah, but that only applies to those documents which
- are of interest to the LDS objective of ensuring that all ancestors have been baptized, and
- whose original owner has permitted the FHL to make available on the website FamilySearch.org.
For my research I need access to thousands of pages of original documents for which those conditions do not apply. All of the suggestions about how to remove original vignetting from such images that I can find here or on other discussion boards are simply too much work to apply to the thousands of images. Since vignetting is an intrinsic problem with any photographic image I do not understand why nobody has developed a filter which models the actual mathematical properties of vignetting.
I am also extremely limited in funding.