Posted-Date: 27 Dec 92 18:46:37 EST
Date: 27 Dec 92 18:46:37 EST
From: Malcolm Blanchard <71530.2536@compuserve.com>
To: <rman@aero.org>
Subject: rendering resolution
Message-Id: <921227234637_71530.2536_DHM49-1@CompuServe.COM>

Donovan Kolbly writes:

> Also, are there any commercial "rendering services" available, which  
> for a nominal fee would render our .rib files at 2400 dpi or so.

Unfortunately, I can't answer Mr. Kolbly's direct question, but I want to
comment on his desire to render at 2400 dpi.  Since Photorealistic RenderMan
(and most other renderers) produce continuous-tone (con tone) output, there
is very little need to ever render an image at anything near 2400 dpi.  A 300
dpi con tone should be sufficient for most imaginable needs.  Imagesetters
operate at 2400 dpi, but they need this to produce smooth line work and text
and to build up accurately shaped and placed half-tone dots.  For half-tone
reproduction, the rule of thumb is to produce a con-tone image at twice the
resolution of the half-tone screen.  Most magazine and catalog work is
reproduced at 150 line-pairs/inch.  Thus they need con-tone images at 300 dpi.
High-quality art reproductions may reach 300 line-pairs/inch, but at that
resolution the 2x rule of thumb breaks down and you could probably still get by
with a 300 dpi con-tone (although 400 dpi wouldn't hurt).

The exception to all of this is if you plan to photographically enlarge the
image after it is transfered to film.  You need to produce sufficient
resolution so that the final reproduction has a resolution of about 300 dpi.
E.g. if you plan on enlarging the image by 2x before printing, you'll need to
render at 600 dpi.

-Malcolm Blanchard