How many frames per second does the human eye see

The history of the birth of cinema is associated with the names of Thomas Edison and the Lumière brothers, who laid down the standards of cinema that their followers adhered to for decades. Gradually, with the introduction of sound, the advent of television broadcasting and digital video, the rules and approaches were transformed.

But invariably, each new technology was forced to take into account the frame rate indicator, which is of great importance in the creation and perception of films by the audience, since the number of frames per second that the human eye can see is limited.

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.

Limits of human vision (how many frames per second can the human eye see)

24 frames per second is not the limit of the human eye. This is the optimal number of frames at which the video sequence is perceived most conveniently: there are no sagging or jumps.

The ability to see also depends on emotions: an excited person is able to perceive more information than a person at rest.

When the cinema was silent and projectionists turned the knobs, they independently chose the speed of the video sequence based on the temperament of the audience: for a calm audience the frequency was 20-24 frames, and for an active one - 24-30.

In order not to be unfounded, we will offer you one resource that clearly demonstrates the frame rate per second - https://frames-per-second.appspot.com. By changing the parameters, you can set your personal vision speed:

When you concentrate your attention on something, you are able to perceive up to hundreds of frames per second, without missing the semantic thread of what is happening. If attention is distracted, the speed of perceived reality drops down to 10 fps

The human eye recognizes a larger number of frames with peripheral vision (and sometimes simply adds speed, as in the case of “moving” circles), and what your gaze is directly directed at is better perceived in slow motion.

The article how many frames per second the human eye sees was published in the section - Educational.

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.

What affects the speed of a computer?

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.

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.

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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Where did the myth about 24 frames come from?

Standard 35mm film after development © Center for Teaching Quality
The myth that the human eye can see a maximum of 24 frames per second is centuries old. 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.

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 many frames per second does the human eye see?

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.