I'm a retired cabinet maker, and I used to cut butt loads od modern MDF and melamine panels. I found I'm allergic to many of those products due to the formaldehyde, but never reacted to masonite. I would never mount a photo directly to the stuff personally, but possibly use it for a backing material behind something else. If someone where to want to mount a photo to it, I would seal it with a good blond shellac first then use a photo grade adhesive.