Lightroom 6.4
Tom Hogarty (tweet):
The goal of this release is to provide additional camera raw support, lens profile support and address bugs that were introduced in previous releases of Lightroom. This release also includes a new Boundary Warp feature for Creative Cloud members.
The direct download link is here (via ProDesignTools).
This is a very simple step-by-step guide [to migrate from Aperture to Lightroom] as I could not find anything with a really detailed description of the process for someone reasonably competent but not expert and who has a highly organised Aperture library of Projects, Folders and Albums!
