Archived posting to the Leica Users Group, 1998/12/31

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Subject: [Leica] Re: PhotoCD scan quality
From: Andrew Nemeth <azn@nemeng.com>
Date: Fri, 1 Jan 99 06:57:29 +1100

emu@aloha.com (Ernest Murphy) wrote:

>Question: Do most processing companies that peddle PhotoCD scanning use
>high-end scanners that can deal with extreme contrast ranges? Scanning
>twice for high and low contrast sounds workable, but is that anything you
>can expect from the people who turn your work into PhotoCDs?

There is no need to multi-scan onto PhotoCD as the 
scan is done & stored in 48-bit, capturing billions of 
colours and light intensity values.  This is way more 
than most desktop film scanners which AFAIK all downsample 
to 24bit before delivering the digital image to you
to manipulate or store.

The trick with PhotoCD is to not just simply open them
in PShop, but rather use Kodak's separate PhotoCD 
Acquire Module (v3) to import the images.  This separate
module will let you adjust the scene brightness, gamma, 
colour-balance *before* downsampling to PShop's 24-bit 
working colour space.

URLs:

Main page...

<http://www.kodak.com/cgi-bin/webCatalog.pl?product=KODAK+Photo+CD+Acquire+
Module>

More tech detail...

<http://www.kodak.com/country/US/en/digital/genInfo/PCDAcquireMod.shtml>

Software download page...

<http://www.kodak.com/cluster/global/en/service/software/pcdAcquireDownload
.shtml>


Granted PShop 5 *will* allow you to manipulate raw 48
bit images, but only in an annoyingly limited fashion.
Much better to downsample to 24-bit - the onscreen 
display is more accurate and it burns up much less RAM 
and disc space too!

So if you have an extreme contrast range image on PhotoCD,
then *acquire* the image twice to grab the highs & lows.
Then merge these using digital dodge & burn.


Regds,

Andrew Nemeth

VR MEDIA  SOUND  PHOTO  JAVA
nemeng  Warrimoo   Australia
www.nemeng.com