Download darktable (2.2.4) Linux – Free

darktable It is a tool photographic postproduction open source, ideal for both professional and amateur photographers. With this application installed on your Linux distribution you can work directly on your photos in RAW format and can manage and handle large amounts of images at once.

Making Life Easier Photographer

basically, darktable It provides the user a virtual darkroom where you can reveal your digital negatives and edit them using different modules including, from the most basic (crop, remove blemishes, change exposure, etc.) to advanced (night vision simulation, among others.).

A serious alternative to LightZone and RawTherapee.

One of the striking aspects of this tool, which unfortunately is not yet available for Windows, is that the RAW image processing is done nondestructively, therefore changes applied will not be permanent until exportes the end result, can reverse the modifications anytime.