There is only one file type that uses the .LUMINAR extension:
Luminar 4 Catalog Database
A LUMINAR file is used to organize images stored in a Luminar 4 image catalog. It contains a SQLite database that associates .TIFF images saved by Luminar with .STATE files that record the edits made to those images. LUMINAR files are stored within the corresponding Luminar catalog folder.
Luminar is a digital photo-editing application that allows photographers to make layer-based edits to their photos. Luminar 4 saves in-progress edits within Luminar catalogs, which are folders comprised of STATE files, TIFF files, and a LUMINAR file, among others.
The LUMINAR file is a SQLite database that Luminar uses to retrieve the TIFF and STATE files stored within a catalog and associate them with one another, so edited images appear correctly within Luminar. Note that, while you can use a LUMINAR file to open a Luminar catalog (as described below), LUMINAR files are not, themselves, catalogs. For example, if you move a LUMINAR file and then attempt to use it to open a Luminar catalog, Luminar will show an error message that says the catalog you are attempting to open cannot be found.
LUMINAR files are not meant to be opened. However, you can use a LUMINAR file to open a Luminar 4 catalog, provided the LUMINAR file is stored within that catalog. To do so, double-click the LUMINAR file or select it after selectingfrom Luminar 4's menu bar.
Updated: June 4, 2020