The two main types of photoreceptors are rods and cones, which differ in both shape and chemical properties. We use cones to see the color. Cones are responsible for the color and sharpness of vision, while rods are used for colorless and weak light. Our world is three-dimensional, so it makes sense that our mental representation of the world has three-dimensional properties. We use a variety of cues in a visual scene to establish our sense of depth. Some of them are binocular cues, meaning they rely on the use of both eyes. An example of a binocular depth index is binocular disparity, the slightly different view of the world that each of our eyes receives. To experience this slightly different point of view, do this simple exercise: stretch your arm completely and stretch one of your fingers and focus on that finger. Now close your left eye without moving your head, then open your left eye and close your right eye without moving your head. You`ll notice that your finger seems to move as you move from one eye to the other, as each eye has slightly different views of your finger. The trichromatic theory of color vision is not the only theory – another important theory of color vision is known as counter-process theory.
According to this theory, color is encoded in opposite pairs: black-white, yellow-blue, and green-red. The basic idea is that certain cells of the visual system are excited by one of the opposite colors and inhibited by the other. Thus, a cell excited by wavelengths associated with green would be inhibited by wavelengths associated with red, and vice versa. One of the implications of enemy treatment is that we don`t feel green-red or yellowish-blue as colors. Another implication is that this leads to the experience of negative afterimages. A residual image describes the continuation of a visual sensation after the removal of the stimulus. For example, if you look briefly at the sun and look away, you can still perceive a spot of light even if the stimulus (the sun) has been removed. When color is involved in the stimulus, color pairings identified in the opposing process theory result in a negative afterimage. You can test this concept with the flag in [link]. Another advantage of this arrangement is that RPE can absorb stray light. This means that your vision is much clearer. Light can also have harmful effects, which is why this setup also helps protect your rods and cones from unnecessary damage.
Rods and cones are located in the innermost layer of the retina. A rod cell is sensitive enough to respond to a single photon of light [how to reference and link a summary or text], and is about 100 times more sensitive to a single photon than cones. Therefore, since rods need less light to function than cones, they are the main source of visual information at night (scotopic vision). Cone cells, on the other hand, require tens to hundreds of photons to be activated. In addition, multiple rod cells converge on a single interneuron, collecting and amplifying signals. However, this convergence comes at the expense of visual acuity (or image resolution) because the aggregated information of several cells is less pronounced than if the visual system received information from each rod cell individually. The convergence of rod cells also tends to make peripheral vision very sensitive to movement and is responsible for the phenomenon of an individual seeing something vague out of the corner of the eye. Rod cells also respond more slowly to light than cones, so the stimuli they receive are added in about 100 milliseconds. While this makes rods more sensitive to smaller amounts of light, it also means that their ability to perceive temporal changes, such as rapidly changing images, is less accurate than that of cones.  There are two types of photoreceptors involved in vision: rods and cones.
Rod cells are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of photoreceptor cell, cone cells. Since they are more sensitive to light, rods are responsible for night vision. Named for their cylindrical shape, rods are concentrated on the outer edges of the retina and are used in peripheral vision. There are about 120 million rod cells in the human retina. Vision is not an encapsulated system. It interacts with and depends on other sensory modalities. For example, when you move your head in one direction, your eyes reflexively move in the opposite direction to compensate for this, allowing you to focus your gaze on the object you`re looking at. This reflex is called the vestibulo-ocular reflex. This is achieved by integrating information from both the visual and vestibular systems (which know the movement and position of the body). You can easily experience this compensation.
First, while keeping your head still and looking straight ahead, wave your finger from side to side. Notice how the finger image looks blurry. Now hold your finger still and look at it as you move your head from side to side. Notice how your eyes move reflexively to compensate for the movement of your head and how the finger image remains sharp and stable. Vision also interacts with your proprioceptive system to help you determine where all parts of your body are and with your hearing system to help you understand the sounds people make when they speak. More information can be found in the multimodal module. Cones are not as sensitive to light as rods. However, cones are more sensitive to one of three different colors (green, red or blue).
The signals from the cones are sent to the brain, which then translates these messages into color perception. However, the cones only work in bright light. That`s why you can`t see color very well in dark places. Thus, cones are used for color vision and are better suited for detecting fine details. There are about 6 million cones in the human retina. Some people can`t distinguish certain colors from others – these people are “colorblind.” Someone who is colorblind may not have a specific type of cone in the retina or a type of cone may be weak. In the general population, about 8% of all men are colorblind and about 0.5% of all women are colorblind. Did you know? Why don`t you see very well the first time you enter a dark room like a cinema? When you enter the cinema for the first time, the cones are working in your retina and the rods are not yet activated. Cones need a lot of light to function properly; The rods require less light to operate, but they take about 7 to 10 minutes to take control of the cones. After 7-10 minutes in the dark, the stems will work, but you will not be able to see the colors very well because the stems do not provide color information.
Cones that provide color information need more light, but don`t work well in the dark. Once the movie is over and you leave the cinema, everything looks very bright and it`s hard to watch for a minute or two. This is due to the fact that the stems become “saturated” and stop working in these light conditions. It takes a few minutes for the cones to work again and normal vision to be restored. The “upside down” organization of rods and cones is useful for several reasons. Photoreceptor: The special type of cell in your eye that picks up photons and then signals them to the brain. They are located in the retina (a layer at the back of the eye). There are two types, stems and cones. Like cones, rod cells have a synaptic ending, an inner segment, and an outer segment.
The synaptic ending forms a synapse with another neuron, for example a bipolar cell. The inner and outer segments are connected by an eyelash.  The inner segment contains the organelles and nucleus, while the outer segment of the stem (abbreviated ROS), which points to the fundus, contains the light-absorbing materials.  While the cones are concentrated in the fovea, where images tend to be focused, rods, another type of photoreceptor, are located in the rest of the retina. Rods are specialized photoreceptors that work well in low-light conditions, and while they lack the spatial resolution and color function of cones, they are involved in our vision in dimly lit environments, as well as our perception of movement at the periphery of our visual field.