Many capabilities of NIH image could not be covered in  a paper of this length.  Among 
these are image arithmetic,  background subtraction, operation of frame grabber cards, 
 and using the rapidly increasing number of plug-ins.  Use of  these is covered in the 
NIH Image Manual. Two useful reference books are Russ 1990 and 1994. Most of the image processing operations described in these books, except for tomography, are available (or soon will be) in NIH Image.
This paper is to intended to give the microscopist hands-on  experience with some of the tools 
provided by NIH Image for  the inspection and analysis of digital images.  Many  
laboratories use it on a daily basis for acquiring images,  sharing data and writing 
papers, as well as for analyzing  images and enhancing them.   
Published research assisted by the use of NIH Image  should use the following quote 
in the materials and methods  section "... analysis performed on a Macintosh <model> 
 computer using the public domain NIH Image program (written  by Wayne Rasband at 
the US. National Institutes of Health  and available from the Internet by anonymous FTP 
from zippy.nimh.nih.gov. 
NIH Image is an indispensable tool for the analysis and  sharing of digital micrographs.