The THX Cinema Certification Criteria states: "The recommended audience viewing angle for the Cinemascope image (2.39:1) from the farthest seat in the auditorium is 36 degrees. THX is a company that certifies commercial theaters that meet certain criteria.
The various viewing distances for Scope are shown in this diagram. Although anamorphic formats have used various aspect ratios over the years, as shown in this table, the modern version (now called Scope) has a standardized aspect ratio of approximately 2.39:1, nominally referred to as 2.40:1 (pronounced "two four oh") or 2.35:1 (pronounced "two three five"). During research in 1953, they determined that the ideal HVA for CinemaScope is 45 degrees at the prime seat, which provides the optimal compromise between picture involvement and picture quality. Ģ0th Century Fox is a film studio that developed an anamorphic format called CinemaScope.
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To complement the effect, the image should be free of artifacts and have a resolution of at least 22 cycles per degree in order to be perceived as sharp. In addition, the viewing distance may be increased beyond 10 feet in order to weaken the viewer's stereoscopic ability to judge the actual distance to the screen, since this ability counteracts the illusion of depth in the image. To improve the sensation of reality, the HVA may be increased beyond 30 degrees in order to induce head movements and reduce the viewer's awareness of the screen itself even further. When the HVA is at least 30 degrees, simple eye movements are fully induced. They recommend that the HVA (Horizontal Viewing Angle) be at least 30 degrees in order to achieve the so-called "induction effect." This effect occurs when the human visual system responds to the image as if it were observing a real-world scene.
NHK is a broadcaster in Japan that developed HDTV, which has an aspect ratio of 16:9. In other words, about half of the viewers prefer viewing distances that are less than it, and the other half prefer viewing distances that are greater than it. Viewers typically prefer smaller viewing angles for smaller screens and larger viewing angles for larger screens. The PVD (Preferred Viewing Distance) is the viewing distance that is chosen by viewers according to their personal preferences. When the actual viewing distance is greater than the CVD, the eye still perceives just as much sharpness (or perhaps even more sharpness), but the eye might resolve fewer details.
When the actual viewing distance is less than the CVD, the eye still resolves just as many details (and perhaps resolves them more easily), but the eye might perceive less sharpness. Since it takes at least one pixel to represent a critical detail, the PPD is 60 at the CVD. With 20/20 vision, the eye can resolve a critical detail that subtends as little as one arc-minute, i.e., 1/60th of a degree. The CVD (Critical Viewing Distance) is the viewing distance where the PPD optimally matches the resolving capability of the human eye. When other types of displays are used, the pixel structure may be more noticeable if they have larger gaps between pixels, or less noticeable if they have smaller gaps between pixels. A PPD between 30 and 35 is borderline in that the pixel structure may or may not be noticeable. When DLP displays are used, for example, the pixel structure is usually noticeable when the PPD is under 30, and it is usually not noticeable when the PPD is over 35. When the pixel structure is noticeable, it is commonly called the "screen door effect" (SDE). Conversely, the pixel structure becomes more noticeable if the PPD is decreased, which can happen as a result of decreasing pixel count, increasing screen size, and/or decreasing viewing distance. The pixel structure becomes less noticeable if the PPD is increased, which can happen as a result of increasing pixel count, decreasing screen size, and/or increasing viewing distance.
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For example, if the PPD is 33.51 on a 1080p DLP display viewed from 1.0W, and the PPD is 33.51 on a 480p DLP display viewed from 2.25W, then the pixel structure is equally noticeable. It can represent how noticeable (or unnoticeable) the pixel structure is. The PPD (Pixels Per Degree) is the number of pixels per degree of the viewing angle.
The following values are provided for comparison in ascending order. Resolution measured in Cycles Per Degree (assuming a typical Kell factor of 70% applied to the PPD) Viewing Distance measured in Screen Heights Viewing Distance measured in Screen Widths The following values are always calculated and cannot be entered. Click the button of the blank parameter to calculate it. Change the selections for Type, Dimension, Units, and Aspect Ratio as desired. One of the four parameters may be left blank. Enter values for any three parameters below.
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