Highly Recommended

RawTherapee is an open source non-destructive image editor and RAW photo processor. It allows you to view and adjustment images, and batch process them via a queue. It is available for Windows, Linux, and Mac.

RawTherapee Website

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Competition

Adobe Lightroom
Darktable

Features

96-bit floating point processing
Supports RAW files from most consumer cameras
Non-destructive exposure and color adjustments, noise reduction, sharpening and more
Batch process or convert files
Copy adjustments between images