I'm not a professional photographer, but if I edit shots, I use GIMP. This is only because it's cheap and I'm cheap too, so things work out. However, it seems like the overwhelming majority of people use Photoshop, and some use Aperture. Because of this, I started wondering why more people aren't using GIMP. Is it because of a lack of features or support, or because it's a hassle to switch programs? How far does GIMP have to go before it's a real alternative to Photoshop for Pro users?
They recently moved from an X11 application to a native app. I haven't tried it out, but there might be some improvements in there.
One of the big problems with the Gimp is that it relies on the GTK toolkit, not the native Quartz, since it is a Linux project, and the GTK-Quartz as used by the Gimp on OSX is painfully slow as well as ugly and stands out like a sore thumb on OSX with poor integration, eg the GTK file menu. As a visual person, it jars, and the way you have to switch focus between the tool palettes and the photo windows is just plain annoying. Mired in GTK, it is just plain too slow and poorly integrated to be taken seriously.
Back when I was interested in Linux, before I got my Mac, I spent some time playing with Gimp and Inkscape and participating in their bugzillas; in the case of the Gimp it left me with the impression they don't have the industry and technical knowhow that Adobe can pay for, ie the best way to convert to black-and-white, or the ongoing issue of CMYK and other colourspaces support, so I basically don't trust it shows me a true representation of the image in its current colour profile. Taking stock of it and Linux's nonexistent colour management and lack of Gamma correction (good luck editing x11 config files or issuing terminal commands every time the screen saver resets the Gamma to 1) led me to abandon both as viable for use in anything to do with graphics (there is a very long list of reasons why Linux was and is unviable for graphics work).
For the Gimp to be viable for Pro work, it has to become truly native (dump GTK), have proper colour management and support various colour spaces like LAB and CMYK, at the very minimum; the latter is tricky to do right as it relates to various Press conditions and must account for dot gain and other print conditions which the printer can specify. Good RAW import support is needed; I know it has some RAW support, but doubt it is much chop, not that I have properly tested it (good RAW conversion is a bit of a dark art). Good lens correction and chromatic aberration correction would be greatly appreciated by photographers as well, something that Lightroom gained with the release of LR4 and Aperture users are waiting for still (where are you, Aperture 4?).
I'm entrenched in the Photoshop way, so I don't care for the Gimp organisation of menus, but that is preferential and harder to judge as to what is "right". Photoshop has a lot of other powerful features, like its collection of Filters and other 3rd party plugins, but whether they are needed depends on the use.
I have Photoshop, and I won't go into how much it costs, but once you use it and know how to make the most of its power, it is just too damn good. For most photography however, I use Aperture (having tried Lightroom 4 for several months exclusively to test it before switching back) mainly because of nondestructive editing of RAW files, metadata management, and the sheer volume of photos makes editing each individual one in Photoshop or any other regular photo editor impractical. For anything beyond adjustment sliders and curves or simple localised brushed-in adjustments, I open it in Photoshop for editing as there is no better substitute. It's RAW support and lens profiles are matched only by Lightroom which use the same engine, and its colourspace support and editing capabilities are similarly unmatched; its engine is based on LAB which can be converted into any other colourspace; LAB editing is a very powerful advanced Pro technique that can yield results that no other way can. For publishing, there is nothing to match it either with its professional CMYK profiles. Moreover, opensource editors like the Gimp can't do duotones using Pantone colours due to patents (same problem Inkscape has, though as an SVG editor it isn't technically meant for printing as SVG only supports RGB).
I have bought Pixelmater, but have only done rudimentary experimentation as it is just too tempting to simply get your work done in something you know well rather than spending a lot of time to see if you can do what you want as effectively as PS. It doesn't currently have adjustment layers, but they are imminent, so I will investigate then. It is very slick looking at least and a lot lighter than Photoshop, so potentially good for quick edits.
