The goal of the lensfun library is to provide a open source database of photographic lenses and their characteristics. In the past there was a effort in this direction (see http://www.epaperpress.com/ptlens/), but then author decided to take the commercial route and the database froze at the last public stage. This database was used as the basement on which lensfun database grew, thanks to PTLens author which gave his permission for this, while the code was totally rewritten from scratch (and the database was converted to a totally new, XML-based format).
The lensfun library not only provides a way to read the database and search for specific things in it, but also provides a set of algorithms for correcting images based on detailed knowledge of lens properties and calibration data. Right now lensfun is designed to correct distortion, transversal (also known as lateral) chromatic aberrations, vignetting and colour contribution of the lens (e.g. when sometimes people says one lens gives "yellowish" images and another, say, "bluish").
Digital photographs are not ideal. Of course, the better is your camera, the better the results will be, but in any case if you look carefully at shots taken even by the most expensive cameras equipped with the most expensive lenses you will see various artifacts. It is very hard to make ideal cameras, because there are a lot of factors that affect the final image quality, and at some point camera and lens designers have to trade one factor for another to achieve the optimal image quality, within the given design restrictions and budget.
In detail: ?more than 40 new database entries of lenses and compact cameras
new CMake based build system for better cross platform compatibility and compilation fixes for MSVC
better integration into hugin for loading and storing lens parameters via the lensfun library
several bug fixes and stability improvements
The source code of the release is available from BerliOS project page.
From now on there will be new releases on a regular basis to frequently bring back database enhancements to the user base. Frequently meaning at least every six months or when there is a significant amount of new profiles.