Path: utzoo!attcan!uunet!aplcen!samsung!think!ames!pacbell!att!watmath!watcgl!imax!dave
From: dave@imax.com (Dave Martindale)
Newsgroups: comp.graphics
Subject: Re: comp.graphics.images
Message-ID: <1989Nov21.181250.13923@imax.com>
Date: 21 Nov 89 18:12:50 GMT
References: <3323@jhunix.HCF.JHU.EDU> <49557@looking.on.ca> <635@alias.UUCP>
Reply-To: dave@imax.com (Dave Martindale)
Organization: Imax Systems Corporation, Oakville Ontario
Lines: 37

In article <635@alias.UUCP> mherman@alias.UUCP (Michael Herman) writes:
>
>For statistics purposes, I have 28 GIF of images of all sorts of
>things.  All are from various BBSs.  They total 2.5 million bytes - I
>would be confident quoting an average of 100K bytes per image (a little
>high but not much).

What are the characteristics of the "average" image that might be
posted to comp.graphics.images (or equivalent).  What resolution, and
how many bits/pixel?  Should there be some agreed-upon upper limit to
these values?

For example, how about sending 1024x768 24-bit images, which are 2.3 Mb
each?  Even 8-bit images of that size are still 790 Kb.

If we go to TV resolution (640x480), images are 300 Kb for 8-bit and
900 Kb for 24-bit.  Are these still too large?  Only when images are
limited to about 256 squared and 8 bits per pixel do you get under the
100 Kb barrier.

Of course, you can't transmit 8-bit raw data over Usenet; it has to be
encoded, which increases its size by 34% or so.  You can save some
space with some images by various encoding schemes, but then everyone
has to have software to decode that format, and no compression schemes
do very well on scanned images, which have a lot of noise.

Also, the compression used in sending news batches typically gets 50%
compression on the text files that make up news articles, but does
considerably worse on image files.  Thus, a 100-Kb image file could
cost up to twice as much money to transmit than a 100-Kb text article.

Ultimately, there needs to be a concensus of how big an image can be
before the cost of sending it outweighs the benefits of distributing
it.  What is this size?

My own opinion is that sending images larger than 50-100 Kb or so is
using too much bandwidth for the potential usefulness of the images.