I've expressed before in these notes the idea that "good art" is work that is evocative, that has emotionally power, with little to no context provided. Good work stands on its own, needing no artist's statement, no little textual description of what it is and what it means, none of that stuff. I have also harped on about the context a viewer brings to a photograph or other work -- which is almost a diametrically opposed point of view, when you mull it over a bit, isn't it?
I think I can refine these ideas a little bit. I rather hope I can, at any rate. At one extreme, let us postulate an alien creature. It communicates with radio waves, it reproduces by fission, it lives on the surface of the sun and has no notion of "vision" as we know it. Communicating even the idea of a photograph to this creature would be difficult. If it did react emotionally to any of our art, it would most likely be in ways that are incomprehensible to us. So, obviously, something is required of art, in particular of a photograph, if it is to move the viewer, if it is to be powerful and evocative. Consider also an illiterate tribe member from your favorite faraway land, or an autistic man from Chicago.
In the interest of simplicity I will describe a photograph as "accessible" to a viewer if the viewer can understand the photograph, and if the viewer reacts to it in some interesting way. The degree to which a photograph is accessible to many people might be termed the "universality" of the image. If absolutely every human on earth found the photograph accessible, we might describe the photograph as universal, or universally accessible, or something of that sort. In general, of course, a photograph is only truly accessible to some people, but the degree to which the photograph moves a wide audience, the degree to which is it powerful to a wide audience of viewers, can reasonably be described as a degree of universality.
In general, it is fair to say that a cultural milieu shared by the photographer and the viewer of the photograph will be a big help in making a photograph accessible. There are really two loosely related factors in play here, one of which is the degree to which a photograph is accessible to the viewer, and the other of which is how much shared context the viewer has with the photographer.
A snapshot of grandma at her 90th birthday party is "accessible" to most family members who know and love grandma, but is most likely inaccessible to anyone else. There is an immense amount of shared context required here to "access" this photograph, which is really the problem with snapshots. This photograph has a very very low degree of universality, it requires a great deal of shared experience to make any sense of at all. Edward Weston's Pepper #30 is far more accessible. Even if the viewer does not know what a green pepper is, the vaguely erotic shapes and tones of the image will likely make some sort of connection for most people. A spike-beast from Tau Ceti might find the smooth textures incomprehensible and certainly not erotic, but human beings will probably find the forms reminiscent of bare human skin. Probably, people who know what a green pepper is will tend to find the image somewhat more accessible. Surely this image is moderately to very universal -- many many people across the world might well find it "accessible" in some interesting way.
Is this notion of universality the same as a notion of "good"? I don't know and I don't really even care. Good art, I think, tends to be pretty universal. Universally accessible things might not always be good art, if you like. It hardly matters, the point here is that universality of a photograph is a real thing, even if we can't really measure it precisely (and I don't care much about that either). Some photographs are more universal than others, and it seems to be a useful way to think about photographs as art, and that's really what I care about.