Robert Shimmin wrote:
Also, greyscale images do not appear to improve OCR with Abbyy either. Although I'm not privvy to their algorithms, certain aspects of the user interface suggest to me that the software only operates on black / white values, and even if you take greyscale scans, the software threshholds them for the purposes of recognition. You have the greyscales to save for whatever other purposes you wish to put them to, but the software itself seems to make use of a B/W version.
I have found, using Finereader 6.0 Corporate, that for certain kinds of material I do get substantially better recognition results from greyscale. The best example are some old medical journals from the 1820's that are severely foxed. Finereader is able to recognize most of the text on these in greyscale, where B&W scanning produced images that even humans can't read. In sizing these down for proofing at DP, I found I could not go to B&W but had to go to 2 bit greyscale, and even then there were a few pages that need the full 8-bit greyscale to be legible. I always scan at 600 dpi B&W with the sheet-fed high-speed scanner because that slows it down enough for me to hand feed it (which is often necessary with the old paper). It doesn't seem to change the recognition quality much either way. JulietS