Aspects of vision
The first thing to understand is that we perceive different aspects of vision differently. Motion detection is not the same as light detection. Another thing is that different parts of the eye work differently. The center of your vision is good at some things, the periphery at others. And one more thing: there are natural physical limits to what we can perceive. Light passing through the cornea takes time to become information on which the brain can act, and our brains can only process this information at a certain speed.
“Computer game players have some of the best eyes. “If you're working with gamers, you're working with a really weird population of people who are probably operating at their highest level,” says Jordan DeLong. DeLong is an assistant professor of psychology at St. Joseph's College in Rensselaer, and much of his research focuses on visual systems.
This is because visual perception can be trained, and action games are especially good for visual training.
“[Gaming] is unique in that it is one of the few ways to significantly improve almost every aspect of your vision, such as contrast sensitivity, attentional ability, and multi-object tracking,” says Adrien Chopin, a cognitive science researcher. So good that games are used in vision therapy.
So before you get angry at researchers who talk about what frame rates you can and can't handle, give yourself a pat on the back: if you play action games, you're probably more sensitive to frame rates than the average person .
How our brain processes reality
First, it's important to understand how you can see images in the first place.
- Light passes through the cornea at the front of the eye until it hits the lens.
- The lens then focuses light onto a point at the back of the eye in a place called the retina.
- Photoreceptor cells at the back of the eye then convert the light into electrical signals, and cells known as rods and cones detect movement.
- The optic nerve transmits electrical signals to the brain, which then converts them into images.
Frame rate: how much visual information does a person perceive?
Frame rate (FPS) is the number of frames changed per unit of time in cinema, television, and computer graphics. In the context of the human eye, FPS is how much visual stimuli can be processed in a given amount of time. Let's figure out how much visual information we can actually perceive.
Brain and reality
Let's start with the basics. Formation of an image in the brain is a complex but very fast process:
- Light passes through the cornea (the surface of the eye) into the lens, which plays an important role in refracting light;
- The lens then focuses the light onto a point at the very back of the eye, the retina;
- Photoreceptor cells in the retina then convert the light into electrical signals;
- Finally, the optic nerve transmits electrical signals to the brain. The latter converts the received data into images.
You can read more about how the visual system works here.
FPS and refresh rate
Whether you're watching a football game from the stands or supervising a child on a bike, your eyes and brain process visual data as one continuous stream of information. But if you're watching a movie on TV or binge-watching YouTube, things are a little different.
A person is accustomed to a frame rate of 24 to 30. For example, all films shot on film have an FPS of 24. This means that every second 24 images flash before your eyes. But not everything you see will have the same frequency. It is also important to consider the refresh rate - how many new images appear on the screen in 1 second. If a monitor's refresh rate is 60Hz (which is standard), that means it is "refreshing" 60 times per second. One FPS roughly corresponds to 1 Hz.
At 60 Hz, the brain processes screen light as one continuous stream rather than a series of constant flickering lights. Higher frequency usually means less flicker.
Is more than 60 FPS fantastic?
60 frames per second is perceived by many as the upper limit of the capabilities of the human eye. However, modern scientific work shows that we can see more.
The authors of a 2014 study from the Massachusetts Institute of Technology found that the brain can process an image in just 13 milliseconds—a very fast speed. Especially compared to the 100 milliseconds that appeared in earlier experiments.
13 milliseconds is equivalent to 75 frames per second.
This may not be the final figure: research on the topic continues today. Source
Eyes and brain work in tandem
The debate about how many frames per second the human eye can perceive has been going on for a long time, largely because there is no clear answer to this question.
As Wiltshire notes, a person does not read reality like a computer, and visual perception is entirely based on the joint work of the eyes and brain. This is why, for example, people see movement and light differently, and peripheral vision is better at some aspects of a picture than primary vision - and vice versa.
The time it takes a person to perceive visual information is the sum of the time it takes for light to enter the eyes, the time it takes for the received information to be transmitted to the brain, and the time it takes to process it.
According to psychology professor Jordan DeLong, when processing visual signals, the brain is constantly calibrating, calculating averages from thousands and thousands of neurons, so the entire system is more accurate than its individual components.
As researcher Adrien Chopin notes, the speed of light can hardly be changed, but it is quite possible to speed up the part of visual perception that takes place in the brain.
Games are perhaps the only way to noticeably improve the basic indicators of your vision: sensitivity to contrast, attention, and the ability to track the movement of many objects at the same time.
Adrien Chopin, cognitive brain researcher
As Wiltshire points out, it's the gamers who are most concerned about high frame rates who are able to process visual information faster than anyone else.
Structure
The human eye perceives visual information using the cones and rods that make up the retina.
These cones and rods perceive video in different ways, but have the ability to combine disparate information into a single picture. Rods do not detect color differences, but are able to detect changing images. How many frames per second does a person see? This is a common question. On the retina of the eyes, photoreceptors are located relatively unevenly; in the center there are approximately the same number of them, but closer to the edge of the retina, rods make up the majority. It is this structure of the eye that has a very logical explanation from the point of view of nature.
In those days, when a person hunted a mammoth, his peripheral vision had to be adapted to catch the slightest movement on the right or left side. Otherwise, having missed everything in the world, he risked remaining hungry, or even dead, so this eye structure is the most natural. Thus, the structure of the human eye is such that it sees not individual frames, as in a storyboard for a cartoon, but a set of pictures as a whole.
Differences in the perception of movement and light
If the light bulb operates at a frequency of 50 or 60 Hz, the lighting appears constant to most people, but there are those who notice flickering in this case. This effect can also be achieved by turning your head while looking at the car's LED headlights.
At the same time, some fighter pilots during tests could see images that appeared on the display for 1/250th of a second.
However, both of these examples do not speak to how the human eye perceives games where movement is the main parameter.
As Professor Thomas Busey notes, at high speeds (latency less than 100 milliseconds), the so-called Bloch's law comes into play. The human eye is unable to distinguish a bright flash that lasted a nanosecond from a less bright flash that lasted a tenth of a second. A camera works on a similar principle, which can let in more light at a slow shutter speed.
However, Bloch's Law does not mean that the limit of human perception stops at 100 milliseconds. In some cases, people can discern artifacts in an image at 500 frames per second (2 millisecond delay).
As Professor Jordan DeLong notes, the perception of movement largely depends on the position a person is in. If he sits still and watches the object, then this is one situation, but if he goes somewhere, then it is completely different.
This is due to the differences between primary and peripheral vision that people inherited from their primitive ancestors. When a person looks directly at an object, he sees the smallest details, but his vision does not cope well with fast-moving objects. Peripheral vision, on the other hand, suffers from a lack of detail, but is much faster.
This is exactly the problem that the developers of virtual reality helmets faced. If 60 or even 30 Hz is quite enough for a monitor that a person is looking at directly, then in order for the viewer to feel normal in VR, the frame rate must be increased to 90 Hz. This is because the helmet also provides a picture for peripheral vision.
According to Professor Busey, if a user is playing a first-person shooter game, then the increased frame rate generally allows him to perceive the movement of large objects better than small details.
This is due to the fact that during the game the gamer does not stand in one place, waiting for enemies, but moves in virtual space using the mouse and keyboard, also changing his position relative to opponents, who may appear in different parts of the monitor.
Where did the myth about 24 frames come from?
The myth that the human eye sees a maximum of 24 frames per second has a centuries-old history. It goes back to the early days of cinema. The first films, made at the end of the 19th century by the Lumière brothers, had 16 frames per second. This figure was chosen because the consumption of standard 35 mm film at this frequency was exactly 1 foot per second. This simplified the calculations of the required amount of film for filming.
The need to increase frequency arose with the transition from silent films to sound films. In those days, the track was written on film next to the picture in the form of strips, each of which corresponded to a certain frequency. The short length of the film scrolled per second (only 30 cm) did not allow the sound to be recorded clearly enough, so the length had to be increased.
They also decided to increase FPS to 24 for a reason. The second film consumption was now 1.5 feet, the minute - 90 feet or 30 yards. These figures also turned out to be convenient for calculations when planning the filming budget. They tried to increase the frequency even more, to 30, 48 and even 60 frames per second, but problems arose.
Such speed required more precise and durable equipment (both for filming and playback in cinemas), and film consumption increased significantly. In addition to the costs of the film itself, the cost of installation and the time required to produce it also increased. In the end, everyone settled on 24 frames; this frequency became the industry standard for many decades.
The frequency of about 25 frames per second was finally approved by the total electrification of Europe and the advent of television. At an alternating current frequency of 50 Hz (changes of direction per second), it is convenient to link 24-25 frames to the current parameters. With this approach, a frame change occurs once per sinusoid period. But in the USA, where instead of the usual 220-230 volts 50 Hz, 110-120 volts 60 Hz is used, the NTSC television standard operates at a frequency of 30 (29.97) frames per second
Why do TV use 24 frames?
Today, the main industry standard is 24 FPS, which suits the modern viewer quite well. However, it was not chosen for theatrical reasons, but for economic reasons . At the stage of cinematography's formation, recommendations for frequency were not developed. The first films had a speed of 16-20 frames/sec , which gradually increased to 22-26, because this level provided optimal sound.
Thomas Edison believed that 46 fps should be used because anything less would strain the eyes. But the industry chose to adopt 24 FPS because it was the slowest frame rate that produced realistic video and maintained optimal audio playback. Filmmakers did not want to use a higher level due to increased financial costs.
The industry currently supports three main standards:
- 24 FPS are used in the American NTSC system, providing clear images and good noise immunity;
- 25 FPS is used in the European PAL or PAL/SECAM system. The value is identical to the NTSC level, since TV broadcasts in Europe are at 50 Hz versus 60 Hz in North America;
- 30 FPS – standard for home theaters and personal video cameras.
Alternative frequencies are also allowed. For example, in the film “The Hobbit,” Peter Jackson used 48 frames , which earned him the wrath of film critics for the hyper-realism of the video. And GoPro Hero allows you to use 90 and 100 FPS options.
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So how many frames per second can the human eye see?
You might wonder what happens if you're watching something at a really high frames per second. Will you really see all those frames that flash? After all, your eye doesn't move at 30 images per second.
The short answer is that you may not be able to consciously register these frames, but your eyes and brain may be aware of them.
For example, take 60 frames per second, which many have taken as the upper limit.
Some research suggests that your brain can actually recognize the images you see in a much shorter period of time than experts thought.
For example, authors from the Massachusetts Institute of Technology found that the brain can process the image your eye sees in just 13 milliseconds—a very fast processing speed.
This is especially fast compared to the accepted 100 milliseconds used in earlier studies. Thirteen milliseconds translates to approximately 75 frames per second.
What is frame rate
The principle of cinema can be understood on the basis of the operation of a simple electro-optical projector. The individual images on the film pass sequentially through the projector mechanism. The built-in lamp directs a light stream at them, through which the optical system alternately projects frames onto the screen, creating the illusion of movement.
For traditional celluloid film, the speed at which images change is expressed in frames per second , or FPS (Frames per Second). For digital films, the concept of “ refresh rate ” is used, which is expressed in hertz (Hz). The higher the indicator values, the faster static images change and the more realistic the illusion of movement looks.
FPS and refresh rate are slightly different. For example, a speed of 24 frames/sec may be characterized by 24 FPS or 48 Hz. FPS refers to the number of individual frames displayed per second. Refresh rate is the total number of times all images are shown during the same time. The fact is that for greater realism and minimizing video intermittency, one frame can be shown two or more times, which is associated with an increase in frame rate.
Are there tests to determine how many frames per second the human eye sees?
Some researchers show a person a quick sequence of images and ask for answers to see what they can detect.
This is what the researchers did to determine that the brain can process an image that the eye only saw for 13 milliseconds.
An ophthalmologist can study movements inside your eye, known as intraocular motion, using high-speed cinematography to learn more about how quickly your eyes work.
These days, even smartphones can capture these subtle movements using slow motion video. This technology allows the phone to record more images in a shorter time.
As technology advances, experts can continue to expand the range of capabilities of the human eye.
How often does the human eye actually see?
The human visual organs are not an artificial device. Therefore, no scientist can accurately determine how many frames per second the human eye perceives. For each individual, the data varies depending on the degree of development of the brain and eyeballs, the speed of nerve impulse transmission, and visual acuity.
In fact, the human organs of vision do not see alternating frames, but the whole picture. The eyes perceive frames only when watching a movie. The surrounding reality is seen by a person as follows:
- as a result of changing the image during movement, it does not matter to a person how many frames per second are formed, the image for him will not change;
- the eyes perceive objects better if they move quickly and sharply;
- If there is a moving object in front of a person’s eyes, then the more frames per second, the better the perception.
It is because of the above factors that we can say that a person sees a picture with an FPS much higher than 24 frames per second. How clearly moving objects are displayed in the human brain depends on the health of the visual organs. If the acuity of perception decreases, the picture will be blurry. With 100% vision, a movie containing not 24, but 60, 100 FPS will be much better for a person.
Not only the number of frames per second affects, but also the following factors:
- frame change amplitude;
- sharpness from the transition to different colors;
- the time required for one frame.
You can glue 100 dissimilar frames together and flip through them quickly. The person will feel discomfort at this time, since the above parameters are not met. An unpleasant sensation is formed due to the fact that the human visual organs try to perceive each frame separately, since they are not interconnected. The subject's eyes and head hurt. If a person has epilepsy, a seizure will begin.
It has been revealed that a person is able to clearly perceive 120-150 frames per second. The number may increase, but the perception will deteriorate. This means that up to 150 frames a person recognizes the image perfectly.
If they increase, it causes discomfort in the eyes and discomfort. It is believed that with a high frame rate, a large number of pictures are shown in one second, the human eye recognizes them smoothly. But even if he doesn’t see the frame change, the brain still perceives it.
If you increase the frame rate, what will happen?
If you show a person one frame per second over a long period of time, over time he will begin to perceive not the individual images, but the overall pattern of movement. However, demonstrating a video image at such a rhythm is uncomfortable for a person. Back in the days of silent films, the frame rate reached 16 per second.
When comparing silent film footage and modern films, one is left with the feeling that they were filmed in slow motion in the early 20th century. When watching, you just want to hurry up the on-screen characters a little. The current standard for shooting is 24 frames per second. This is the frequency that is comfortable for human vision. But is this the limit, what is beyond this range?
Now you know how many frames per second a person sees.
The term frame rate (fps) was first used by photographer Eadweard Muybridge. And since then, filmmakers have been tirelessly experimenting with this indicator. From the point of view of practicality, it may seem that it is unreasonable to change the number of frames per second, because a different number will not be visible to the human eye.
How many fps does the eye perceive? We know that 24. Does it make sense to change anything? It turns out that all these efforts are paying off. Modern gamers, and just people who use computers, can say this with confidence.
The principle of cinema can be understood on the basis of the operation of a simple electro-optical projector. The individual images on the film pass sequentially through the projector mechanism. The built-in lamp directs a light stream at them, through which the optical system alternately projects frames onto the screen, creating the illusion of movement.
For traditional celluloid film, the speed at which images change is expressed in frames per second, or FPS (Frames per Second). For digital films, the concept of “refresh rate” is used, which is expressed in hertz (Hz). The higher the indicator values, the faster static images change and the more realistic the illusion of movement looks.
FPS and refresh rate are slightly different. For example, a speed of 24 frames/sec may be characterized by 24 FPS or 48 Hz. FPS refers to the number of individual frames displayed per second. Refresh rate is the total number of times all images are shown during the same time. The fact is that for greater realism and minimizing video intermittency, one frame can be shown two or more times, which is associated with an increase in frame rate.
Scientific background
Scientists have proven that at a 24-fold frame rate, a person perceives not only the overall picture on the monitor, but also individual frames on a subconscious level. For game developers, this information became an incentive to conduct further research into the capabilities of the human visual organs. Amazingly, the human eye can perceive video at a speed of 60 frames per second or more. The ability to perceive more images increases when you concentrate on something. In this case, a person is able to perceive up to one hundred frames per second without losing the semantic thread of the video image. And in the case when attention is scattered, the speed of perception can drop to 10 frames per second.
When answering the question of how many fps the human eye sees, we can safely name the number 100.
How many FPS can the human eye see?
Physiologically, the human eye is capable of perceiving up to 1000 FPS . This is because the myelinated optic nerves are capable of firing 300 to 1000 times every second and transmitting signals at a speed of 90 m/s. However, experiments show that a person processes and sees on average up to 150 frames over a designated period of time. There are rare cases where, with regular training, a perception level of about 250 FPS was achieved. But some researchers believe that the human eye can perceive even 1000 or more frames per second.
How is research carried out?
Experiments in the field of identifying the capabilities of the human visual organs are constantly being carried out, and scientists are not going to stop there. For example, they conduct the following testing: a control group of people watches the proposed videos at different frame rates. Frames with some kind of defect are inserted into certain fragments at different periods of time. They depict some kind of extra object that does not fit into the general outline. It could be a fast moving flying object. In all groups, more than 50% of subjects notice a flying object. This circumstance would not be so surprising if it were not for knowing that this video was shown at a frequency of 220 frames per second. Of course, no one was able to examine the image in detail, but even the fact that people were simply able to notice flickering on the screen at such a frame rate speaks for itself.
Research
Since this topic is interesting to many people, the number of experiments carried out is also large. After all, everyone wants to know about the capabilities of their vision. One of the most unusual and amazing experiments can rightfully be considered the following:
When a group of subjects watched a high-frequency video, they noticed an extra object on the screen.
- Scientists created groups of people.
- They were provided with video material that contained barely visible defective frames depicting something superfluous. Usually it was a flying object.
- After watching, a significant portion said that they noticed the flickering in the video.
- This amazed everyone, as the fps was at 220.
You can do a small experiment yourself at home and test the abilities of the visual system. There are a number of videos with different frame rates for this purpose. After viewing, it is worth recording observations at this moment. However, it is better to avoid 25 frame material.
When creating virtual reality helmets, developers encountered a problem. It turned out that the peripheral does not distinguish details, but has greater speed. Therefore, it was necessary to change the value of 30 and 60 hertz, which are suitable for monitors. After several attempts, it turned out that for a comfortable stay in a helmet, this value should reach 90 Hz.
How many frames per second does the eye actually see?
Human vision is not a discrete system whose capabilities can be described in simple numbers. This can be said about the camera: it writes video in a resolution of 3240x2160 pixels, with a frequency of 60 frames per second. And the human eye sees exactly the frames only if it looks at the developed film or the digital video storyboard in the editor.
The visual system perceives the picture holistically, noticing only its changes. Therefore, there is no specific figure indicating the limits of the eye’s capabilities. If the picture does not change, there is no difference; 5 frames, 25, or 250 will change per second. The limits of perception strongly depend on the characteristics of the observed object. The faster it moves, the sharper these movements, the higher the limiting frequency.
Comparison of 5, 10, 15 and 30 frames per second on a slow picture
Watching a video of a person slowly walking in a straight line, the eye will not notice a significant difference between 24 and 60 frames per second, since the movements are smooth. If this person runs fast, there will already be a difference; a video at 60 FPS will seem much smoother and more enjoyable than at 24 FPS. And if this person does not just run, but runs in a zigzag, jumping over obstacles along the way, then even the difference between 60 and 120 FPS will be noticeable, in favor of a higher frequency.
Comparison of 12, 18, 25 and 60 fps on dynamic video
You don't have to go far to check this out. It is enough to run a heavy game on your computer first at low settings to get high FPS, and then at high or maximum settings to get less than 30 FPS. You will immediately notice the difference: in the first case, although the objects will be less detailed, the movements will be much smoother.
Seeing the difference between 30, 60 and 100 FPS, you can clearly see that the human eye sees much more than 24 frames per second. The limit after which the difference becomes invisible depends on individual vision, and in the case of a video or game it is 80-150 frames per second, and sometimes more.
The mechanism of human video perception
The human eye begins to identify the change of still pictures per second as intermittent movement when their number reaches 12. When the frequency moves into the range of 18-26 frames/sec, the viewer observes a moving scene and perceives it as video . If the FPS value is low, then the animation looks uneven, and if it is too high, the effect of hyper-realism appears.
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One of the main components of creating realistic video is motion blur . When we observe objects around us, we miss the detail when they move quickly. In other words, we do not have enough time to perceive complete visual information and visual acuity is lost. In cinema, this effect is achieved by blurring, which occurs naturally when changing frames. But if the FPS level is too high, then this effect disappears, and the observer sees a hyper-realistic picture. This prevents him from believing what is happening on the screen.
Unexpected facts
Not everyone knows about this interesting fact: experiments with displaying video images at different frequencies began more than a hundred years ago in the era of silent films. To show the first films, film projectors were equipped with a manual speed control. That is, the film was shown at the speed with which the mechanic turned the handle, and he, in turn, was guided by the reaction of the audience. The original speed of silent film was 16 frames per second.
But when watching a comedy, when the audience was highly active, the speed was increased to 30 frames per second. But this ability to arbitrarily regulate the display speed could also have negative consequences. When the cinema owner wanted to earn more, he, accordingly, reduced the showing time of one session, but increased the number of sessions themselves. This led to the fact that the film production was not perceived by the human eye, and the viewer remained dissatisfied. As a result, in many countries, at the legislative level, the demonstration of films at an accelerated frequency was prohibited and the standard in accordance with which projectionists worked was determined. In general, why are fps and the human eye studied? Let's talk about it.
More about eye sensitivity
The first silent films mentioned at the beginning of the article were shot at 16 frames per second. This allowed for film consumption to be kept to a minimum (1 foot per second) without losing the effect of movement on the screen. In addition, it was more convenient to calculate the amount of film required for the film. These films looked completely different from modern ones: the movements of the actors were sharp, accelerated, they clearly lacked smoothness and lightness.
But at that time people perceived them almost as reality. Thus, it is clear that with the number of frames per second equal to 16, the human eye already mistakes them for movement. Although they may appear slightly sharp, sped up, or angular, the eye and brain cannot differentiate between the individual images, mistaking them for one whole - movement.
When cinema became sound, the number of frames increased. This was required so that sound could be recorded on a special track next to the frames. With this innovation, the actors’ movements on the screen became smoother and more natural, making it easier for the viewer’s eye to perceive them.
The 24-frame mode, invented a little later, was optimal both technically and aesthetically. But over time, the number of frames only increased, and the quality of shooting improved.
Today, regular video is approximately 60 frames per second, and 3D video is 90 frames per second.
Let's sum it up
Your eyes and your brain do a lot of work processing images—more than you might realize.
You may not think about how many frames per second your eyes can see, but your brain uses all the visual cues to help you make decisions.
As scientists continue their research, we can learn more about what our eyes and brains are able to see and understand.
Sources
- https://droidnews.ru/skolko-vsyo-zhe-kadrov-v-sekundu-sposoben-vosprinimat-chelovecheskij-glaz
- https://impulsa.ru/health/fps-glaza-cheloveka/
- https://dtf.ru/gamedev/3705-skolko-kadrov-v-sekundu-vosprinimaet-chelovecheskiy-mozg
- https://zen.yandex.ru/media/hyperu/skolko-kadrov-v-sekundu-vidit-chelovecheskii-glaz-5c49faef5770a000afcc5a9b
- https://proglazki.ru/interesnoe/skolko-fps-vidit-chelovecheskij-glaz/
- https://FB.ru/article/343306/skolko-kadrov-v-sekundu-vidit-chelovek-stroenie-glaza-i-interesnyie-faktyi
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