What the Eye Does Not See
It can be interesting to compare. Human beings and cameras both have forms of selective vision, focusing on some things and missing others entirely.
Point a camera at something and frame the image. That frame divides the world in two. Everything inside the frame will be in the image. Everything outside the frame won't be. Yes, some of what the camera doesn't see may still makes its presence known indirectly. A light source outside the frame may cast light on what the camera sees, or another object may cast a shadow. Animals in the frame may react to the presence of what they can see but the camera can't. But for the most part, what gets cropped out may as well not exist.
Human vision has a frame as well, but it's less clearly bounded. No one has eyes in the back of their head, but attempts to find precisely where the edges of the frame in front of us are will be met with resistance. Look to the corner of your eye and your field of vision moves too, shifting the frame along with it. Glance, even in passing, in one direction and you will temporarily not see in the opposite direction. But we're generally only partially aware of the shifting frame.
What we think we see differs to a degree from what we actually see. Our vision isn't so much what our eyes see as what our brain tells us we are seeing. We live in a mental map that is constantly being updated based on input from our senses. Turn your head one way and that map gets extended to cover the added territory. Our certainty about what lies on the other side decreases, but our belief in what is there doesn't disappear completely. We still think we know what is there, and to an extent still believe we can see it because we so recently did see it.
An object may fall within the frame and thus be visible, but it may not be seen clearly. The effect of focus and depth has similarities too between us humans and our cameras yet also significant differences. A camera is focused at just a single distance, with the apparent degree of clarity falling off progressively in front of and beyond that distance. Human eyesight features selective yet dynamic focus that shifts as looks for, and focuses on, what we find interesting, and looks right past what doesn't strike our fancy. Our mental visual map may include selective perceptions built from any number of focus distances and directions to construct a seemingly enveloping reality that only partially exists in reality as a unified whole.
Here's an experience I can relate that you may have had as well. While casually wandering around, looking for something to photograph, you notice a couple things that together seem like they'd make a great shot — perhaps a rushing stream and a mountain peak. Both appear to be sufficiently in line with each other to have the makings of a great composition. You stop to investigate further though only to realize that that magical shot isn't actually possible. Position yourself to where you can get the stream perfectly framed the way you envisioned and you find that you can't actually see the peak beyond due to an intervening hillside. Stand back to where you can see the mountain the way you wanted and the stream shrinks in scale and impact leaving too much wasted frame, creating confusion as to what exactly the intended subject is. The great looking stream and the great looking mountain both do exist, but not together at the same time from any point in the real world despite what your brain initially told you it thought was possible. Essentially, you only imagined such a shot was possible.
Without sufficient attention to detail to examine things clearly, you'd certainly go home and tell everyone about the magnificent vista you had come across. Our brain may trick us, but a camera keeps us honest. It objectively honors the literal boundary of the frame. It exists at a single point in space and remains true to the spatial relationships and focus distance of what can actually be seen from that point in a single image.
So what are we to make of all this? The world we perceive around us is a composite of images and perceptions gathered from our recent experiences. Our camera perceives the world more literally, and from only one vantage point at a time. We could look at this as making our efforts at photography more difficult since we can't always capture the images we think we see. But it is also possible to look at this as a secret weapon in our quest for great images.
You can find a lot of great vistas at the ends of long windy roads. That's of course precisely why those long windy roads got built — because people wanted to be able to easily see those sights. When I go up to the North Cascades, the Sunset Highway out of Bellingham, Washington leads to the Mount Baker ski area. But the road continues beyond that for an additional short stretch until it reaches Artist Point, a place whose very name tells you the sights there must be good — and they are. That last mile or so of road wasn't built so that people could test their driving skills on hairpin turns. It was built so that people could see what lies at the end of the road, and the trails that stretch out from there.
But taking pictures there can sometimes be challenging if you want to picture the natural world in its seemingly pristine beauty without man's intrusions. Other people go there too, and expect some degree of infrastructure and amenities. The snow melts late there and comes early again in the fall closing the road again for the season. The window of opportunity to visit Artist Point is short, and as with most great vistas at the end of long windy roads, you will not be alone most of the time. Taking pictures without other people and other distractions isn't always easy.
When I stand there and look, the view is magnificent. But I'm not necessarily seeing exactly what I think I am. Because we don't want to see those other people, we ignore them. We look right past them for the most part. Those trail marker signs fall to the same fate. We mentally erase them as being inconvenient unless we need them to determine where we are and which trail to take. But my camera can't do that.
On the flip side though, it's more rigid delineation of the image frame can become an advantage if I can find a position to shoot from that crops out what I don't want to see. I can set my tripod right next to that trail marker sign and not even see it through the viewfinder. Whereas I have to ignore it when looking at things, my camera can't even see it at all. By seeing only what it actually sees, a camera can sometimes be positioned to create images that humans can't easily replicate. And I can get my camera right up on top of a small patch of flowers so that they fill the foreground and create an image that looks as if the entire hillside is covered in flowers. The camera doesn't see what I crop out, and a viewer looking at the resulting image later is left to assume that what I show them is representative. Maybe in a good year when that hillside was covered it would be. In a bad year with less rainfall when there are fewer flowers though I can sometimes still come home with the same image. All it takes is an understanding how a camera sees rather than being limited by how I do myself.
So it all depends on how you want to look at it. The differences in how a camera sees versus how we ourselves see can be viewed as both a curse and a blessing. It's your choice. As with everything else, it's just another aspect of the tools we use as photographers. If you understand the differences, you can use them to your advantage.