Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: Notesfiles $Revision: 1.6.2.16 $; site datacube.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!decvax!cca!datacube!shep
From: shep@datacube.UUCP
Newsgroups: net.graphics
Subject: Solarization and Posterization
Message-ID: <6700033@datacube.UUCP>
Date: Thu, 19-Sep-85 21:28:00 EDT
Article-I.D.: datacube.6700033
Posted: Thu Sep 19 21:28:00 1985
Date-Received: Sun, 22-Sep-85 23:57:58 EDT
Lines: 32
Nf-ID: #N:datacube:6700033:000:1542
Nf-From: datacube!shep    Sep 19 21:28:00 1985


Solarization and Posterization. We here these terms and most of us
familiar with them picture the effect mentally:  An image with some
type of luminance or chromanance quantization and/or mapping. But
what do they REALLY mean and what are their origins?

I believe solarization came from the photographic effect of exposing
emulsion to light sometime during development. 
I have no idea where the term posterization came from.

Can anyone answer these questions? I worked on a popular television
special effects box that has what I called solarization and posterization.
The solarization name was given to all the lookup table effects performed
on only the y (luminance) signal. As we quantized luminance to progressively
fewer states, we said the image was more "solarized". Similarly, the
"posterization" term was applied to quantization of the chromanance
difference components. 

I recently received mail from a friend asking me about the subject...

>Subject: solaraposterization
>Just what are solarization and posterization?  You are the world expert on
>these matters now that you have become an ancient one. ...
>Is a table look-up on luma and chroma independently enough or do
>you have to provide LSD-like cross leakage between luma and chroma?

and I remembered that I had found references that spoke of quantization
in polar (hue/sat/val) space. Does anyone know of these references or
algorithms?

Shep Siegel                           UUCP: ihnp4!datacube!shep
Datacube Inc.; 4 Dearborn Rd.; Peabody, Ma. 01960; 617-535-6644