The effect of film film projector in digital video technology
Good day to all Habravets. Surely, many of you love to go to the cinema, in this amazing and something attractive world. Surely, many photographers, videographers, cameramen and editors thought about how to make their final product more interesting and similar to a movie.
Inspired by photography and video editing at one point, I thought, the resulting picture is too realistic and not at all like a “movie”. Having rummaged through the Internet, no solutions for this problem were found in an easy way, except for the effects of adding all kinds of dust, dashes, hairs and scuffs, like on a film. In addition, watching the latest films in FullHD format, with its very realistic and lively picture, also deprived of this cinema magic . I had to go on an expedition and carry out excavations - research of the subject area.
Since we do not get this effect of cinema magic , let's compare our home, digital technologies and analog cinema projection technologies.
Definitely clear that the whole thing in the frame rate of video. Frequency in video / movie is the number of frames played per second. The more frames are played per second, the more vibrant and realistic the image on the screen is. Well, and, accordingly, on the contrary, within reasonable limits, because if the frequency is, for example, 1 fps, then this is more like a slideshow.
')
So what do we have? Digital SLR cameras record video of about 30 fps, and (somehow it has historically been) in the cinema this number is 24. "So this is the solution!", I thought, and ran to remake my video from 30 to 24 fps . But it was not there! Of course, the difference was noticeable, but it was not like a movie. Even an attempt was made to cut the video into separate and static picture frames (so that everything was fair, that everything was like on a film - 1 frame and 24 such frames for one second), and their reverse gluing in the video does not look like a movie and everything here! We dig further.
Now look at the film film projector deeper. Film film projector is a mechanical device in which frames are turned over, and the light from a powerful lamp, passing through a film frame and a lens system, creates an image on the screen. The device, I must say, is very interesting, and, as usual - not very complicated. A feature of the film projector is the device - obturator . The obturator blocks the luminous flux during the frame change when pulling the film to avoid blurring the image on the screen. It turns out that the light passes through the positive (film frame) directly at the moment of its immobility and fixation (positive). What do we have? The frame is fixed - the light goes through it, the frame changes - the obturator blocks the light. Usually, the obturator is a disk with cuts rotating in front of the projector lamp through which the light is transmitted / blocked.
We try to put this knowledge into practice. To do this, we again cut the video into images and insert images with darkness between them (i.e., moments when the frame is changed and the light is blocked).
It turns out that our "scheme number 1" has the form: 1 frame + dark + 2 frame + dark + ... and so on. Those. in a second we play 48 individual images.
Result: everything flickers, the overall image is incomprehensible, it is unpleasant to watch. We continue to dig the subject area further.
It turns out that there is some trick in the cinema department. In order to reduce the flickering of the film when changing the frame, a shutter with an additional blade (open + closed section) is used, such a blade is called a blank blade. As you might have guessed, when the obturator is in the idle zone, the frame does not change. This allows you to create a flicker frequency of the projector 48 Hz, but to play all the same 24 frames per second. We apply in practice.
Now our “scheme No. 2” looks like: 1 frame + dark + 1 frame + dark + 2 frame + dark + 2 frame + dark + 3 frame + ... and so on. 96 images are played per second.
Result: Flicker less, the picture can be distinguished, but watching such a video will be quite short because of the unpleasant flickering. We dig further.
Film projectors have one constant, it is called the coefficient of obturation . The coefficient of obturation shows the ratio of the length of the open region of the obturator to the period of frame change in the projector. For example, in the 23KPK Soviet film projector, the coefficient of obturation is 0.57, i.e. during the lifetime of one frame, the duration of its illumination is 57% of the total lifetime of this frame. In addition, the shape of the shutters is different: as flat, cut sections from the disk from the center in a straight line (as if it were similar to the BMW badge), and with all sorts of curved cuts or slots.
It is also worth noting that the overlap of the light flux with a disk obturator with straight cuts from the center (and indeed with any other obturator) does not occur immediately, and not instantly, and not even from top to bottom, but in a straight line from the radius of the disk during its rotation. So does the opening by the shutter, not immediately, and not exactly from top to bottom. Also, as we know, light has a very high speed (and the speed of opening / closing by the shutter of the light flux is insignificantly small compared to the speed of light), which means that the work of the shutter is fully reflected on the silver screen, although this is not noticeable to us.
The image output to the monitor also occurs frame by frame, with a specific and specific frequency. Of course, it is possible to create a simulation of the film projector effect in digital technologies when working with images at high frequency. For example (back to our “scheme number 2”), playing 400 images to work out only one cycle (1 frame + dark + 1 frame + dark), 120 of which show the frame, then 80 images show a neat drawing of the imitation of the disk obturator - close and opening the image of the frame, then again 120 pictures are showing the frame, and closing the cycle - 80 images of the shutter operation to close this frame and open the next frame. And this is only the life cycle of the first frame, as if it were an analog projector. For one second of video, 9600 such digital images will be required.
My 4th nuclear PC began to work strangely when playing 250-300 digital images per second. And if we add here the monitor response time (the minimum time for which the pixel changes its brightness), which tends to be different for different models, so that the problem is solved for most monitors? Solution of the problem in a universal form is most likely possible, but most likely not worth it.
A rather interesting result has the “scheme No. 3” of the form: 1 frame + 1 frame + dark + 1 frame + 1 frame + dark + 2 frame + 2 frame + dark + 2 frame + 2 frame + dark. That allowed to reduce flicker and increase the brightness of the video stream (and simulate the work of the instantaneous shutter with a coefficient of 0.66). But at the same time the number of images played per second was equal to 144. The effect of the movie is still far because of its sharpness when changing and being noticeable to the eye when perceived.
Here it is - the mechanical technology of analogue film projection, the effect of which is not so easy to imitate on digital technology.
Thanks to all. The area is very interesting, as well as its history, I advise.
Materials:
Obturator - Wikipedia
Movie Projector - Wikipedia
Inspired by photography and video editing at one point, I thought, the resulting picture is too realistic and not at all like a “movie”. Having rummaged through the Internet, no solutions for this problem were found in an easy way, except for the effects of adding all kinds of dust, dashes, hairs and scuffs, like on a film. In addition, watching the latest films in FullHD format, with its very realistic and lively picture, also deprived of this cinema magic . I had to go on an expedition and carry out excavations - research of the subject area.
Since we do not get this effect of cinema magic , let's compare our home, digital technologies and analog cinema projection technologies.
Definitely clear that the whole thing in the frame rate of video. Frequency in video / movie is the number of frames played per second. The more frames are played per second, the more vibrant and realistic the image on the screen is. Well, and, accordingly, on the contrary, within reasonable limits, because if the frequency is, for example, 1 fps, then this is more like a slideshow.
')
So what do we have? Digital SLR cameras record video of about 30 fps, and (somehow it has historically been) in the cinema this number is 24. "So this is the solution!", I thought, and ran to remake my video from 30 to 24 fps . But it was not there! Of course, the difference was noticeable, but it was not like a movie. Even an attempt was made to cut the video into separate and static picture frames (so that everything was fair, that everything was like on a film - 1 frame and 24 such frames for one second), and their reverse gluing in the video does not look like a movie and everything here! We dig further.
Now look at the film film projector deeper. Film film projector is a mechanical device in which frames are turned over, and the light from a powerful lamp, passing through a film frame and a lens system, creates an image on the screen. The device, I must say, is very interesting, and, as usual - not very complicated. A feature of the film projector is the device - obturator . The obturator blocks the luminous flux during the frame change when pulling the film to avoid blurring the image on the screen. It turns out that the light passes through the positive (film frame) directly at the moment of its immobility and fixation (positive). What do we have? The frame is fixed - the light goes through it, the frame changes - the obturator blocks the light. Usually, the obturator is a disk with cuts rotating in front of the projector lamp through which the light is transmitted / blocked.
We try to put this knowledge into practice. To do this, we again cut the video into images and insert images with darkness between them (i.e., moments when the frame is changed and the light is blocked).
It turns out that our "scheme number 1" has the form: 1 frame + dark + 2 frame + dark + ... and so on. Those. in a second we play 48 individual images.
Result: everything flickers, the overall image is incomprehensible, it is unpleasant to watch. We continue to dig the subject area further.
It turns out that there is some trick in the cinema department. In order to reduce the flickering of the film when changing the frame, a shutter with an additional blade (open + closed section) is used, such a blade is called a blank blade. As you might have guessed, when the obturator is in the idle zone, the frame does not change. This allows you to create a flicker frequency of the projector 48 Hz, but to play all the same 24 frames per second. We apply in practice.
Now our “scheme No. 2” looks like: 1 frame + dark + 1 frame + dark + 2 frame + dark + 2 frame + dark + 3 frame + ... and so on. 96 images are played per second.
Result: Flicker less, the picture can be distinguished, but watching such a video will be quite short because of the unpleasant flickering. We dig further.
Film projectors have one constant, it is called the coefficient of obturation . The coefficient of obturation shows the ratio of the length of the open region of the obturator to the period of frame change in the projector. For example, in the 23KPK Soviet film projector, the coefficient of obturation is 0.57, i.e. during the lifetime of one frame, the duration of its illumination is 57% of the total lifetime of this frame. In addition, the shape of the shutters is different: as flat, cut sections from the disk from the center in a straight line (as if it were similar to the BMW badge), and with all sorts of curved cuts or slots.
It is also worth noting that the overlap of the light flux with a disk obturator with straight cuts from the center (and indeed with any other obturator) does not occur immediately, and not instantly, and not even from top to bottom, but in a straight line from the radius of the disk during its rotation. So does the opening by the shutter, not immediately, and not exactly from top to bottom. Also, as we know, light has a very high speed (and the speed of opening / closing by the shutter of the light flux is insignificantly small compared to the speed of light), which means that the work of the shutter is fully reflected on the silver screen, although this is not noticeable to us.
The image output to the monitor also occurs frame by frame, with a specific and specific frequency. Of course, it is possible to create a simulation of the film projector effect in digital technologies when working with images at high frequency. For example (back to our “scheme number 2”), playing 400 images to work out only one cycle (1 frame + dark + 1 frame + dark), 120 of which show the frame, then 80 images show a neat drawing of the imitation of the disk obturator - close and opening the image of the frame, then again 120 pictures are showing the frame, and closing the cycle - 80 images of the shutter operation to close this frame and open the next frame. And this is only the life cycle of the first frame, as if it were an analog projector. For one second of video, 9600 such digital images will be required.
My 4th nuclear PC began to work strangely when playing 250-300 digital images per second. And if we add here the monitor response time (the minimum time for which the pixel changes its brightness), which tends to be different for different models, so that the problem is solved for most monitors? Solution of the problem in a universal form is most likely possible, but most likely not worth it.
A rather interesting result has the “scheme No. 3” of the form: 1 frame + 1 frame + dark + 1 frame + 1 frame + dark + 2 frame + 2 frame + dark + 2 frame + 2 frame + dark. That allowed to reduce flicker and increase the brightness of the video stream (and simulate the work of the instantaneous shutter with a coefficient of 0.66). But at the same time the number of images played per second was equal to 144. The effect of the movie is still far because of its sharpness when changing and being noticeable to the eye when perceived.
Here it is - the mechanical technology of analogue film projection, the effect of which is not so easy to imitate on digital technology.
Thanks to all. The area is very interesting, as well as its history, I advise.
Materials:
Obturator - Wikipedia
Movie Projector - Wikipedia
Source: https://habr.com/ru/post/180271/
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