Message-Id: <mailto:199412231923.NAA18715@library.wustl.edu> Date: Fri, 23 Dec 1994 11:18:44 -0800 From: Brian Sullivan <mailto:bsullivan@GETTY.EDU> Subject: Re: scanning pencil writing 2 -Reply -Reply To: Multiple recipients of list IMAGELIB
Image quality is much more than dpi. The problem stated indicated there may be a problem with dynamic range (bits per pixel) capture, not dpi.24-bits per pixel is marginally meaningful in explaining the captured dynamic range (dynamic range˙termediate shades between the max and min density values of an image). I do not know the dynamic range capability of the HP deskscan, but I'm rather confident it is significantly lower than that of a PIW scanner.
Current PIWs capture at a dynamic range of 2.8 (around 630 levels per color plane), which is sufficient for capturing the full range of negative film (note: it is not sufficient for capturing the full range of a well exposed transparency (pos film)). This data is then intelligently reduced to a YCC format to retain a maximum amount of luminance information#linear 8 bit data equates to 256 levels). Most of this information can be accessed using an appropriate photoshop (kodak) plugin (some will clipping occur).
There are some good white papers and articles on photoCD (and photoCD images) that you may be able to obtain from Kodak Technical Services at 800-242-2424 (? ext x19?). Suggested articles: (a) Graphic Arts News, Vol 1, #4 (b) Fully Utilizing Photo CD Images, Article No. 1 - Using Information Beyond 100% white (c) Kodak Photo CD Products, A Planning Guide for Developers. Further explanation may also be found within Rudolph Burger's small paper back book "Color Management Systems"
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