Light reflected from the objects we gaze at creates the pictures we perceive. Because the front of the eye is curved, light is bent, resulting in an upside-down picture on the retina. The brain finally flips the image around. Thus, we see the world as it is actually located in space.
The lens of the eye focuses images onto the back of the eyeball. This is why cameras are usually built with the lens on top of the sensor; this also makes the camera easier to use since you can look through the lens while taking photos.
There are two muscles that control the shape of the lens and thus its ability to focus images: the ciliary muscle and the zonule. The ciliary muscle lies behind the lens and it can pull on the fibers that connect it to the lens capsule to change its curvature. The zonules are attached at one end to the lens capsule and at the other end to the ciliary body. They are very thin filaments made of collagen and elastic tissue that support the lens inside the eye. When they are relaxed, their normal shape is a circle but when they are activated, their shape becomes an ellipse.
When you look at a distant object your ciliary muscle contracts and bends the lens in a way that brings the object closer to it.
How do the eyes function? Without this process, there would be no way to see objects as they really are instead of how they look upside down through our lenses.
This phenomenon explains why images appear upside down in early photography. The camera lens was flat and images were turned by hand before being exposed onto film. As technology has improved, so has the ability to take perfect photographs automatically. Today's cameras use sensors with millions of pixels that can detect even a single ray of light. The human eye can only detect about 7 million pixels, so cameras can capture much more detail than humans can see.
Upside-down images may also appear in paintings, drawing, and sculpture. Artists work from life, but since people are right-handed, most art is left-sided. To make things match up, artists turn right-handed objects left-side up. This is why you often see left-hand written directions on right-hand driven countries.
Finally, upside-down images may appear in dreams. Dreams are recreations of thoughts and feelings from the previous day or longer.
They are light sensitive but not color sensitive. That's why inverted images look black and white.
The human visual system is very efficient at processing information. When we see a face, for example, the eyes are usually the first thing people notice, so it makes sense that neurons would be activated when viewing an image of eyes. Neurons that respond to light coming from the back of the eye would be used by the brain to recognize faces because people have two eyes on their head and they want to make sure they are getting all the information they can from each eye.
Inverted photographs are useful tools for scientists to study how the brain processes images. Some experiments have shown that if you show subjects inverted images of objects such as chairs or houses, they tend not to recognize them later. This may be because the brain is using information from the whole image to make a judgment, not just the shape of the object. In other words, the eyes and the rest of the image contribute to what the brain decides is a "chair."
Inverted photographs have many other applications too.
This setup has an unusual peculiarity in that our eyes view things upside down mechanically. That's because the process of refraction via a convex lens flips the picture, resulting in a totally inverted image when it reaches your retina. Your brain then reassembles the image into its proper orientation.
The fact that the retina is attached to the back of the eye means that it must be located behind the lens. Thus, when the lens bends light from objects behind it, only certain parts of the image reach the retina. All other parts are blocked. The result is that only certain parts of the image get focused on the retina, while the rest is ignored. This is why you see images flipped upside down on the retina.
The human retina contains two types of photoreceptors: rods and cones. Rods are most numerous, making up 95% or more of all retinal cells. They are very sensitive to light but have a narrow focus; thus, they need to be stimulated many times per second for clear vision. Cones account for about 5% of retinal cells. Because they are sensitive to color, they are responsible for our ability to see detail such as shadows and contrasts in colors.
Rods are highly sensitive to light but have a narrow focus. Thus, they need to be stimulated many times per second for clear vision.
An picture focused on the retina by the human eye is ALWAYS inverted: top to bottom; right to left. This was true at birth and will continue to be true throughout life. This is due to the anatomical structure of the optics of the eye and its lens system. The lens can rotate but it cannot change direction.
The brain then inverts this image before sending it to the rest of the body for processing. This process occurs rapidly within a fraction of a second. Thus, an image seen by the eyes "upside down" on the retina is immediately inverted by the brain before it can be perceived as such.
Here are some other things that may not be what they seem:
A shoe is always right side up, even though it might appear to be upside down.
A tree is always right side up, even though it might appear to be upside down.
A compass always points north, even though it might appear to be pointing south.
Atoms are the basic building blocks of matter. They have three distinct parts: head, torso, and leg. A full stop is a punctuation mark used to indicate the end of a sentence or paragraph. It is a small punctuation mark consisting of two crossed lines over a point.
When we flip images upside down, we can perceive lines, forms, tones, and light much more clearly and vividly. It also attempts to discern forms and negative space. As a result, when we work by turning designs upside down, we can simply verify ourselves and examine dimensions. Drawings are still useful even if you are not sure about exactly how things should look.
Upside down drawing helps us see clear shapes and forms that might otherwise be hidden. The eye is naturally drawn to the upper-most part of an image, so by flipping it over we can see everything else too. Lines, shapes, and colors will appear in a new light when viewed this way. When you turn drawings upside down, you are actually seeing them in reverse perspective...which means that larger objects are going to cover up smaller objects when they're turned upside down!
Upside down drawing is helpful for visualization purposes. If you've got trouble imagining something, drawing it can help give your brain some material with which to work. You can show yourself what it would look like if something were done in a different way, or try out different styles. There are no right or wrong answers when you draw something from imagination, so go ahead and have fun!
Upside down drawing is also good for developing focus and attention to detail.