"IMHO": Getting Into GIMP

Sharpening: Unsharp Masking (USM)

GIMP's USM is located under Filters --> Enhance --> Unsharp Mask. The basic parameters look much the same as in PS, however the numbers/multipliers are different, so don't try to apply Photoshop settings directly here. Of course, if you do try PS's (much higher) numbers, you'll immediately notice the difference in the preview window.

Polyglot's recommended initial pass, as you can see, is conservative (untouched image is the one on the right, behind the USM window):



Setting the threshold at 20 prevents sharpening of the noise in the shadow area (if you can't immediately see the sharpening, compare the patches of writing reflected on the pen).

Another approach is to apply a stronger USM, then 'fade' the effect. Immediately after you apply the USM [or certain other actions], an option to 'Fade [whatever]' will appear in the Edit menu.





(notice you can also set the blend mode, default is 'replace')

the effect (left- high USM [before], right- faded USM [after])




Edited by Turerkan - 15 April 2009 at 11:30

Enabling 3rd-party Photoshop Plug-Ins (*.8bf files)

This is something I wish to dwell on. The GIMP is capable of employing a significant number of third-party Photoshop (abbreviated as PS) plug-ins, --those in the *.8bf format-- but only after first downloading and installing a special plug-in called PSPI.exe, which can be found here. Scroll to the bottom of that page, download the appropriate file for your operating system, and install the plug-in in GIMP's main plug-in directory (path -- C:\Program Files\GIMP-2.0\lib\gimp\2.0\plug-ins -- on a Windows machine with default install location). Then startup GIMP, and you'll find a new feature in the "Filters" menu:



click on that option, because you have another step to perform; you will be presented with a dialogue box for setting up the directory in which you will store all of the Photoshop plug-ins. Click in the field indicated below:



then click the folder/browse icon (circled below)



Navigate where you like & create a new folder for Photoshop plug-ins. Put all of your future *.8bf plug-ins in that location. (You can see the location I chose in the screen capture above).



Sample Plug-ins & Install

As noted on the home site of the PSPI plug-in, a few, totally free Photoshop plug-ins are available from Flaming Pear (scroll to the "free plugins"). Download the .zip file, and copy the *.8bf files to your Photoshop plug-ins directory. You don't need the extraneous *.html files or images from the zip file, just the *.8bf files. Whatever you choose to copy is thereby installed, and GIMP will recognize the new filter(s) when you next start the program. Here I've copied just the one filter, and it now appears in the Filters menu, under Flaming Pear:



One, free, third-party Photoshop plug-in I occasionally make use of is Virtual Photographer. I learned of VP from a sharpening tutorial here on Dyxum, called "Meet Frank," written by MiPr. It is, unfortunately, a Windows-only plug-in (the difference, I guess, is that VP relies upon a number of Win-only support files that won't work in Linux).

To install this particular plug-in, download the installation program, then direct the installer to put the plug-in file in your Photoshop plug-ins directory as created in the process outlined above. Restart GIMP, and you'll find the new filter, just so:



It should be noted that VP only works on color/RGB images, not on grayscale images. So you have to make sure the image "mode" is set to RGB, otherwise the plug-in will be 'grayed out' or inaccessible.



Edited by Turerkan - 15 April 2009 at 11:29

Getting Into GIMP
an article by alpha_in_exile




Introduction

     (taken from Turerkan's article A Day With GIMP with a few edits, you can pass this section if you read it) Being there, interpreting the scene, composing and clicking the shutter. Is this all you need in the way of making a good picture? Sadly it is not, and you have got a lot to do even after taking the shot.

     The other important aspect of photography is post processing. Photographers have varying opinions about processing, but I think its safe to say we all agree processing is a fundamental part of photography. It can't be left out, even when you don't manipulate the photo directly, it is still manipulated in many ways. For example, you can't avoid taking the picture through an optical lens, your sensor or film will have a tone response different than your eyes, and there is RAW conversion in digital photography. Even if you take “in camera JPEGs”, they still go through RAW conversion, but inside the camera.

     If manipulation is unavoidable, then the photographer will want to take control of the process if possible. We don't want our pictures to be just a randomly generated interpretation of the scene right? We want it to be our interpretation! This is where post processing comes in. Adding artistic values to a picture by means of processing requires a skill different than photography. However I believe that every photographer should at least be able to extract a realistic interpretation of the scene from his original shots.

Most image processing software is very expensive and hard to master. There are many programs to choose from, each appealing a different group of photographers. It may take many trials to find a program for your needs and your budget might not be enough for your favourite one. There are exceptions tough, thanks to the open source software community we have some free image processing programs available. The most developed and famous one is GIMP. It has a feature set nearly rivalling the Photoshop, state of the art in the industry.

• GIMP; is free, both for commercial and personal use.


• works under most operating systems, including Windows, Linux and Mac OS X.


• is a general image processing program, very similar to Photoshop. You can use it for all graphical works.


• is extendable by means of scripts, GIMP plugins and Photoshop plugins.


• can handle most image formats.


• can convert RAW files with the UFRaw plugin

• However; it works in 8 bits per channel, only UFRaw can process 16 bits with RAW files which then are coverted to 8 bits.


• Requires installing UFRaw for RAW compatibility. This is a trivial process though.


• has an unusual user interface that may take time getting used to.

Links

The GIMP Project
Official GIMP Website | Documentation | Tutorials | Plugin Registry

Extras
Essential plug-in with many advanced post-procesing features, GREYC's Magic Image Converter
Compilation of all current scripts, GIMPfx Foundry
A general purpose high pass filter script, High Pass Filter
There is a Debian package for GIMP Plugin Registry items called gimp-plugin-registry
Plugin to enable usage of third party Adobe Photoshop Plug-ins, PSPI
For some Photoshop plug-ins to begin with, Flaming Pear | OptikVerve

Learning
Video Tutorials | Color Management | Smart Sharpening in HSV Colors | GIMP User Community

Edited by Turerkan - 05 May 2009 at 20:07