I'm not trying to argue that one should look at the colorization of "art photos" as a repair/restoration. Artists of all kinds indeed choose their medium carefully, and their work is, well, their work. It's an expression of their choices made in response to the constraints of the time. The best way to conserve art, is to try to restore it to exactly the way it was when the artist created it; not to try to second-guess the artist.
But most photos are not intended as art. Most photos are candids (or portraits, or photojournalism.)
Or, to say that another way: most people who take "photos"—both historically, and today—are not "photographers" by profession, trying to paint with a lens and film. They're just people who want to preserve a view of something, and have a convenient technology for doing just that.
If you want a general policy on how to conserve photos, it should be based around the idea that unless you know better, you should assume that the taker of a photo very likely wasn't an artist choosing their medium for effect; but rather a person constrained by the media available at the time of the photo's creation. Most photos that were taken in the period when B&W photos were the only photos you could take, were not intentionally B&W. If given the option, a color photo would have been taken instead. These photos are, in est, "damaged" color photos. As if the taker expected a color photo, but due to bad camera settings, a B&W photo was taken instead. The equivalent of a photo taken when there was a hair on the lens—an incidental aberration.
Just like, for example, most photos taken at 320x240, when that was the best quality a digital camera could give you, were not intentionally taken at 320x240. It was just the fact of the photo-taker being unable to afford a fancy film camera and rolls of film, but indeed being able to afford an early-2000s webcam and no rolls of film.
Or, for another example, most people who recorded mono audio of themselves onto wax cylinders, early reel-to-reel tape, etc., weren't going for the "mono audio mix-down sound." They just were in possession of only a single-track audio storage or distribution technology. Remastering the sound with source-separation more faithfully achieves the sound they wanted to record, but didn't have the technology for. (Do the surviving Beatles disapprove of the stereo remasterings of their mono albums? No; they think they're grand!)
I think we actually broadly agree. I was thrown by the mention of art conservationists, but probably took it too literally.
When it comes to archival conservation and restoration, it seems to me that there are two opposed goals which both have value: restoring to the highest-quality version we possibly can, and preserving the material as it would have appeared to its original audience. So for the wax cylinder example, we definitely want to produce the best, truest to intent restoration we can, but at the same time the experience of listening to a wax cylinder recording is also worth preserving.
As long as the restoration is non-destructive (which it always should be, with digital tools), that’s great! We can have it both ways.
There’s an interesting modern twist when it comes to vernacular photography, too. The popularity of instagram filters and the like suggests that there’s something more going on now even with snapshots.
But most photos are not intended as art. Most photos are candids (or portraits, or photojournalism.)
Or, to say that another way: most people who take "photos"—both historically, and today—are not "photographers" by profession, trying to paint with a lens and film. They're just people who want to preserve a view of something, and have a convenient technology for doing just that.
If you want a general policy on how to conserve photos, it should be based around the idea that unless you know better, you should assume that the taker of a photo very likely wasn't an artist choosing their medium for effect; but rather a person constrained by the media available at the time of the photo's creation. Most photos that were taken in the period when B&W photos were the only photos you could take, were not intentionally B&W. If given the option, a color photo would have been taken instead. These photos are, in est, "damaged" color photos. As if the taker expected a color photo, but due to bad camera settings, a B&W photo was taken instead. The equivalent of a photo taken when there was a hair on the lens—an incidental aberration.
Just like, for example, most photos taken at 320x240, when that was the best quality a digital camera could give you, were not intentionally taken at 320x240. It was just the fact of the photo-taker being unable to afford a fancy film camera and rolls of film, but indeed being able to afford an early-2000s webcam and no rolls of film.
Or, for another example, most people who recorded mono audio of themselves onto wax cylinders, early reel-to-reel tape, etc., weren't going for the "mono audio mix-down sound." They just were in possession of only a single-track audio storage or distribution technology. Remastering the sound with source-separation more faithfully achieves the sound they wanted to record, but didn't have the technology for. (Do the surviving Beatles disapprove of the stereo remasterings of their mono albums? No; they think they're grand!)