I'm kind of surprised that we've never seen an in helmet view of Clonetroopers/Stormtroopers/Mandos showing what they see in a movie/show. The old EU said they have targeting cues linked to their weapon so they would see a target mark in their helmet based on where the blaster is pointing. That way they wouldn't always have to aim down sights to hit things. I would assume they could turn that on/off so they could target through sights or through the helmet cue.
Don't you know about the Stormtrooper helmets?
They don't have any provisions to see at all. It's just a solid mask in front of them. George Lucas explained it in a magazine interview one time.
That's why none of the troopers can ever hit a barn door with blaster. They are aiming wildly based on their hearing alone.
They walk around by peeking their eyes downwards out the bottom of their helmets. That's why they all jog so slowly and never really run. They can't see more than a few feet ahead of them. They don't want to get chewed-out by their commander for not hustling, so they make a big show of jogging but they are trying not to move forwards too fast for fear of stumbling on something.
Think of the scene in ANH when Luke is practicing lightsaber stuff on the Falcon. Obi-Wan tells him to try it with the helmet's blast shield down. It totally blocks his view. Why would such a stupid blast shield exist if it was feasible to make a transparent one? It's not feasible, which is why the Stormtroopers have to deal with solid-face helmets.
The troopers' shooting accuracy is actually pretty good based on hearing. It's necessary for them to be combat-effective at all. That's why Obi-Wan noted the precise blast hits at the Sandcrawler massacre in ANH. The troopers' commander probably let them briefly take off their helmets to attack the Jawas, figuring that the hits would be more precise than usual (and look more like Sandpeople did it). But the troopers ended up being
too precise without the helmets and Obi-Wan saw through the ruse.
Why would stormtroopers ride around on those slow clumsy Dewback creatures on Tatooine? They should be using some kind of hovering mechanical craft like a Landspeeder, right? The answer is because they can't see in their helmets to steer any high-speed craft. The Dewbacks do the driving for them. (Notice that the biker scout troopers on Endor were using different helmets from regular stormtroopers. It was a compromise in armoring to allow them to steer the speeder bikes. The Endor stormtroopers who were on foot were still using regular helmets.)
Remember during ANH in Mos Eisley, when the troopers stopped Luke & Obi-Wan to ask about their droids? It was easy for Obi-Wan to fool them because the troopers couldn't actually see the droids very well.
Remember during ANH when Obi-Wan went to turn off the Death Star's tractor beam controls? He used the Force to sneak past a pair of troopers standing around talking. He was in clear view of them both and they never saw him. But he used the Force to make one minor noise in the other direction and they heard it.
The clearest demonstration of the solid-faced helmets was during ANH on the Death Star. Three stormtroopers were breaking into the control room where the droids had been left, and one of them walked right into the top of the door with his head. It makes sense when you realize he could see a few paces ahead down at floor level, but his view was totally blocked at head level.
George Lucas said the whole blocked-face helmet thing was intended to be symbolic. The troopers think the Empire is morally right because they can only see their most immediate surroundings. They can't see any farther ahead. They can't see the larger picture of what the Empire is doing to the galaxy, which is why they are willing to participate in it. It's an example of the Vietnam War's influence on early Star Wars.
