Microfilm scanners are a wonderful invention, and I'm so enamored with them that in writing this post I browsed the web to see what they cost. At least as much as the top of the line Apple Powerbook and maybe as much as a VW Passat to put it in terms of other desirable items. Of course, the relative prices may change. Not buying any of those things for myself any time soon ...
Anyway, here's my tip for your microfilm scanning. As best I can tell what the scanner does is similar to what an automatic focus camera does—sensing the relative amounts of white and black in the viewfinder and then capturing the image. Now if you've ever taken photos on an automatic camera you'll know they are easy to fool by composing a shot that is a mix of both dark and light areas. Same goes, it seems, for the microfilm scanners.
If you have significant amounts of the black film between the pages in your images, the digital image will not be as well exposed for the part of the image you want. Previously my preference when using the microfilm scanner was to have the black space on the side of the page, rather than cropped parts of another page. This works OK for pages that are quite dark anyway (whole pages of text). It works poorly when you are trying to capture an image of a page that has a lot of white space in it—tabular data, for example—because then the automatic exposure settings can't cope very well, and will wash out the detail you are interested in.
Bottom line advice is this: For the best exposure on microfilm scanners try capturing an image without any of the black film space between pages.Posted by eroberts at October 20, 2006 2:21 PM | TrackBack