Bolts are cool. There's a surprising amount of engineering going on there, and a lot of stuff to talk about when you've got a bolt and an application for it. There's tensile strength (how hard it it to pull apart lengthwise), shear strength (how hard it is to tear sideways), stuff about threads. When you tighten down the nut to a specific torque, you're applying tension to the shaft of the bolt and "using up" some of the available tensile strength, but there are reasons for why you might do that, and so on. There are probably entire textbooks on the subject.
The stuff we build, like ships, uses a lot of bolts. Naturally, when we're designing a ship, we spend a certain amount of time thinking about bolts and bolt engineering. Actually, a surprising amount of time. We don't want the damned thing to fall apart, after all. That's super awkward.
But the ship is not the bolt, nor vice versa. When we're designing a ship, we're doing Naval Architecture, which is a complete discipline. It includes much, only a piece of it is strength of materials, only a little bit of it is about bolts. The Naval Architecture piece allows us to calculate the way our bolts will be loaded, which enables is to do the right bolt engineering.
Again: the Naval Architecture is what we're doing. The bolt stuff arises as a consequence of the ship's demands. Occasionally, we might find that our ship doesn't even use bolts. Everything is glued or welded.
And so it is with the photograph. There's a lot we can say about the photograph, about groups of photographs, about how these things work. While these notions are often necessary to understand how, say Instagram works (as a social construct, how it works "in total" as it were), or how Law Enforcement Surveillance works, they are not sufficient.
In order to make sense of how law enforcement's gradually increasing photographic surveillance works, you need to know quite a bit about law enforcement, social systems, bureacracies, and also a bit about photography. The last one on the list is not going to magically imbue you with enough understanding of the previous. Indeed, we will only really deploy our understanding of photography when it becomes salient as we work out what the hell is up with the police. We might find, sometimes, that while visuals are in play, they're not even particularly relevant. Our dissertation on "index and representation" never even gets pulled out of its drawer (to our vast disappointment).
I am, naturally, as guilty of this as anyone else. But I try to be conscious of it, and I try to do Naval Architecture as appropriate, rather than hoping that my understanding of bolts will carry me safely through to the complete ship design. Probably not 100% though. Dang it.