Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!princeton!udel!thomson
From: thomson@udel.EDU (Richard Thomson)
Newsgroups: comp.graphics
Subject: Re: Computerized Enhancement of Pictures
Message-ID: <432@louie.udel.EDU>
Date: Thu, 13-Aug-87 09:34:16 EDT
Article-I.D.: louie.432
Posted: Thu Aug 13 09:34:16 1987
Date-Received: Sat, 15-Aug-87 08:48:11 EDT
References: <5013@ihlpa.ATT.COM>
Reply-To: thomson@udel.EDU (Richard Thomson)
Organization: University of Delaware
Lines: 32
Keywords: How?

In article <5013@ihlpa.ATT.COM> hhm@ihlpa.ATT.COM (Mayo) writes:
>Where can I find information about the computerized enhancement of 
>black and white pictures to recover images not apparent on the original
>print. How is it done? Is it applicable to film? What reference sources 
>are available?
>                                                  Larry Mayo

I believe what you are referring to is called contrast enhancement.  The basic
idea is to take a histogram of the image and redistribute the small range in
grey scale over the entire range from black to white.  There is a very good
reference on this technique as well as others for processing images using a
computer.
	_Picture Processing_, (Azriel) Rosenfield & Kak

This was the textbook in a course I took on image processing.  Rosenfield is
an old-timer in the field of digital image processing.  He reviews articles
for the IEEE Computer Graphics & Applications magazine and has published
at least two editions of this book.  The latest edition comes in two volumes,
although the information on contrast enhancement is in the first volume.  I
don't have the second volume, so I don't know what's in it. :-(

As far as its applicability to film, you would probably want to take an
'average' histogram to find a contrast expansion scheme that would uniformly
increase the contrast in the whole film.  I imagine that if you treated each
frame as a separate photograph, light scenes would be darker and dark scenes
would be lighter than desired

						Rich Thomson
-- 
Rich Thomson		Aspiring Grad Student	  ARPA: thomson@louie.udel.edu
Forget Mars, we've got business on the Moon.	  UUCP: don't know
OS/2: Yesterday's software tomorrow