[Leica] The GIMP info (LONG!)

[Martin Howard <mvh@media.mit.edu>]

OK, this is what I know about using GIMP as a digital darkroom.  I'm not an
expert, but I'll try to include as much information as possible as a
starting point for your own exploration and fact finding.

Some background info:

  * I haven't used the latest version of Photoshop: I've used Photoshop
    version 3.something pretty extensively on an M$ Windows NT platform.

  * I run GIMP 1.0.2 on a Silicon Graphics Indy machine, using IRIX 6.5
    OS and the 4Dwm X-Window manager.

  * I've used Photoshop much more extensively than I've used GIMP.

  * I'm not a religious fanatic when it comes to free software or
    the GIMP... ;)  I use it because it's free, powerful, and runs
    on the machines I have access to.

Ease of use: Compared to Photoshop, I find GIMP equally easy/difficult to
use.  The layout of menus is pretty close to the Photoshop `standard'.  I've
had about as much difficulty in both programs, mostly because I'm not 100%
familiar with terms like `levels' and `curves', but that's just part of the
learning curve.

If you try to run GIMP on a platform for which there are no precompiled
binaries, you will have to build the program from the source code.  All the
source code is supplied, along with Makefiles, but it still is far less
trivial than just moving a binary executable into the right location.

The GIMP has an online manual, and I *think* there might be one or more
books printed on how to use it, but I'm not 100% sure.  There is only little
documentation of a `how to use'-nature that comes with the downloaded files,
but there are many sites dedicated to the GIMP.  (I've just checked the
GIMP links: there are at least three books in English, one of which is
called `Teach yourself GIMP in 24 hours'.)

Gamma correction: GIMP itself, as far as I know, doesn't have gamma
correction.  I do that in the OS, because SGI machines have a program that
lets you adjust the gamma.  Maybe someone has written a plugin for gamma
correction in GIMP itself: I don't know.

Software modules: Since I don't do my own scanning, I haven't looked into
modules that correct for artefacts left by film scanners.  Check the URL at
the bottom of the message for the homepage of the GIMP plugins.

GIMP uses the printer drivers of the operating system to generate printer
files, like any intelligently written piece of software should.  So, if you
have the drivers installed, then GIMP should be able to use them.

What I liked about the GIMP over the version of Photoshop that I used is
that it has some automation, and is extensible.  Features such as
Autostretch HSV or Normalize Contrast are great for getting the most out of
a scanned negative and Auto Levels does a good job of putting some punch in
my pictures.

The tools I use most are curves & levels for adjusting tonal ranges.  I like
the colour balance that lets you adjust shadows, midtones & highlight
separately (just like Photoshop).  Undo is limited by (a) memory and swap
space and (b) by how many levels you set in the preferences dialogue.

There are channels (including alpha) and layers, much like Photoshop.  The
selection tools are an improvement over the version of PS I've used. Using
Bezier curves and a little feathering you can isolate pretty much anything
perfectly from it's surroundings.  Selections can be saved to a channel.

It's main advantage, though, is Script-Fu, a scripting language that can be
used to write extensions (plug-ins are a different thing and are written in
C/C++-code and linked with the GIMP libraries).  Many of these are chiefly
of use to those designing art from scratch, or webpages, but some are useful
to the digital darkroomer.

URLs:  The GIMP Homepage is at:   http://www.gimp.org/

GIMP news page: http://www.xach.com/gimp/news/index.html

A list of plugins can be obtained from:   http://registry.gimp.org/

The GIMP manual page:  http://manual.gimp.org/

Before and after shot of GIMP plugins:
    http://www.xach.com/gimp/previews/cubism.html

Very nice before and after shots for filters, plugins & script-fu:

    http://www.infotech.tu-chemnitz.de/
   ~nt/marb/glaeser/gimp-plugins/html/index.html

   (you'll have to reconstruct the link above: just remove the linebreak)

The GIMP Important Links page:  http://www.gimp.org/links.html


So, Eric, when do we see the corresponding list for Photoshop...? ;)


Good luck!

M.

- -- 
Martin Howard                                 (__)                 (__)
Visiting Scholar at MIT Media Lab |           (oo)                 (OO)
fax: +1-617-253-8874              |    /-------\/       ~~~~~~~~~~~~~~~~~~~~
email: mvh@media.mit.edu          |   /|     ||
www: http://mvhoward.i.am/        | ~~~~~~~~~~~~~~
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