<HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="GENERATOR" CONTENT="Mozilla/4.01 [en] (Win95; I) [Netscape]"> <TITLE>2. Scanning Concepts</TITLE> </HEAD> <BODY TEXT="#000000" BGCOLOR="#FFFFFF" BACKGROUND="../icon/body.jpg"> <CENTER><B><FONT FACE="arial"><FONT COLOR="#FF7D00"><FONT SIZE=+2>Chapter 2. Scanning Concepts</FONT></FONT></FONT></B></CENTER> <P><B><FONT FACE="arial">2.3 Resolution and Sizing</FONT></B> <BR><B><FONT SIZE=+1>Depending</FONT></B> on the contents of your documents, basically, we can classify them into three image types. <P><A NAME="a"></A><FONT COLOR="#FF7F00">2.3.1 Resolution</FONT> <BR><B><FONT SIZE=+1>Resolution</FONT></B> determines the level of detail recorded by the scanner. <BR><B><FONT SIZE=+1>Image</FONT></B> quality will improve with higher resolution, but after a certain point, what we called "optical resolution", it won't get any visible improvement to the image even with increase resolution. <P><B><FONT SIZE=+1>The</FONT></B> difference between "optical resolution" and "maximum resolution"? <LI> Optical resolution is the "native" resolution of the scanner, determined by the optics of the scanner hardware( for example: 300 x 600 dpi scanner, 300 dpi is the x-coordination resolution determined by CCD (Charge-Coupled Device) and 600 dpi is the y-coordination resolution determined by the steps of motor per second).</LI> <LI> Maximum resolution is the resolution enhanced through interpolated algorithm. Interpolated resolution is useful in scanning line art or enlarging small originals, however, maximum resolution is inferior to optical resolution in some image quality and crispness.</LI> <P><A NAME="b"></A><FONT COLOR="#FF7F00">2.3.2 Image Size</FONT> <BR><B><FONT SIZE=+1>A</FONT></B> large image size could lower the system performance of your computer dramatically. The file size is affected by the selected area, file format, scaling percentage, resolution and the image type. Please refer to the following table (file compression is excluded): <TABLE BORDER > <TR> <TH>Image Type</TH> <TH>Description</TH> <TH>Image Size (Bytes)</TH> </TR> <TR> <TD VALIGN=TOP>1-bit images</TD> <TD VALIGN=TOP>Black and White Line Art or Halftones</TD> <TD>(Height x Width x Height resolution x Width resolution) x (Scaling percentages) 2 /8</TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#1">8-bits</A> images</TD> <TD VALIGN=TOP>Black and White or Color Photo, 256 gray levels or 256 colors</TD> <TD>(Height x Width x Height resolution x Width resolution) x (Scaling Percentages) 2 x 8 ) /8</TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#2">24-bits</A> images</TD> <TD VALIGN=TOP>Color Photo, Millions of Colors</TD> <TD>((Height x Width x Height resolution x Width resolution) x (Scaling Percentages) 2 x 24 ) /8</TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#3">30-bits</A> images</TD> <TD VALIGN=TOP>Color Photo, Billions of Colors</TD> <TD>((Height x Width x Height resolution x Width resolution) x (Scaling Percentages) 2 x 30 ) /8</TD> </TR> </TABLE> </BODY> </HTML>