Erik,
As others have said, Salgado is indeed known for having made digitally-acquired images which were subsequently exhibited as silver gelatin prints.
I confess I do not know the details of Salgado's workflow offhand. But producing film copies of digitally-acquired motion picture "film" images uses technology which has become quite sophisticated. The best known is probably ARRI AG's Arrilaser, which writes digital image files—either digital-originated files, or scanned and edited files from film-originated footage—to film, using solid state RGB laser technology. A 21st Century evolution of the kinescope if you like. There are other firms (such as CELCO) that have been active in the area of film recorder manufacturing.
The application of this technology may be for archival purposes, or—less-common these days, obviously, in the era of digital cinema projection—because film-out cinema release copies are desired. Tarantino's The Hateful Eight comes to mind as one motion picture in recent years that was actually shown on projected film at selected cinemas (and 70 millimetre, at that!). Years ago, one of my brothers used to service Arrilaser film writers in Australia for ARRI.
I know nothing about how prevalent writing digital still images to film is or the potential cost of same—and I admit, I'm now more curious about the details of Salgado's workflow. But the technology exists—ARRI were at one time given an Academy Award for their work in this area (and also for their digital Arriflex Alexa cameras, but that's another matter).
Cheers,
Brett
