What is Anamorph? Complete detail of anamorphic Video format

Anamorphic Video format

What is Anamorph?

Anamorph is a film or video format in which a widescreen image is horizontally compressed (optically or digitally) to a standard 4: 3 aspect ratio. The correct geometry of the image is restored during playback by “stretching” the image to its original aspect ratio (without loss of resolution).

a cinematic method shooting a widescreen picture on the standard 35 mm film. This also applies to the projection format. In which the distorted image is “stretched” by the anamorphic projection lens to recreate the original aspect ratio on the viewing screen.

Anamorp video Resolutions

  1. NTSC 720×480 4: 3 Arrow720x540 (640×480, ITU * 720×528, 654×480)
  2. NTSC 720×480 16: 9 Arrow853x480 (854×480, ITU 872×480)
  3. PAL 720×576 4: 3 Arrow768x576 (ITU 785×576)
  4. PAL 720×576 16: 9 Arrow1024x576 (ITU 1047)

Anamorphic resolution is indicated on the right

Anamorph Equipment

An anamorphic lens consists of a conventional spherical lens and an anamorphic attachment (or integrated lens) that performs an anamorphic effect.

The anamorphic element works at an infinite focal length. So it practically does not affect the focus of the main lens on which it is installed. The anamorphic operator uses a spherical lens with a different focal length than they would use for the Academy format. While the anamorphic lens compresses the image to half-width. There were other anamorphic attachments that expanded the image vertically the frame is twice as large. No matter how high it is filled with the available film area. In any case, since the same image was recorded over a larger area of ​​the film, the image quality improved.

Why is Anamorph needed?

Most of us are used to thinking that pixel(the smallest logical element of a two-dimensional digital image) is extremely square. This opinion is erroneous. Pixels are also rectangular. As you know, the resolution of a DVD-Video stream is usually NTSC 720: 480 = 1.5 or PAL 720: 576 = 1.25. Which does not correspond to any television/cinema format. In this case, the frames of the film may not correspond to this resolution at all. So it was necessary to come up with some way to record the original frame on DVD with its frame (720×576 or 720×480). That is why they began to use anamorphic resolution when recording video.

How does this happen?

We take the original frame and place it in16: 9 (or 4: 3)format, adding black stripes at the top and bottom if necessary. Then the resulting frame is horizontally compressed to DVD format (720×576 or 720×480). In this case, the whole picture visually becomes, as it were, elongated vertically. Here, now we have received a frame of the DVD format, which is subjected to compression:

What does it do?

When watching a video with an anamorphic resolution, you will need to do the opposite. Therefore, the frame is first expanded. Then stretched to a 16: 9 ratio (or 4: 3 depending on the original ratio), and we get a normal aspect ratio

DVD Options

Full Frame

For DVD, this means that the 4: 3 source image has been transferred directly to the DVD.

Pan & Scan

For DVD, this means that the image is initially widescreen and is transferred to DVD. But the player itself demonstrates this image, not as widescreen. But as 4: 3, using the same technique as the transfer operator – analyzing the picture.

Naturally, the player itself cannot analyze the picture. For this, during mastering, special marks are placed that allow the player to determine which part of the widescreen picture to show on a regular TV at that moment. In fact, the picture is slightly zoomed.
It should be noted that today, there are only a tiny number of disks that have this function (special labels), and therefore many confuse this model with the Full Frame mode.

Letterbox

Widescreen picture transferred to DVD (black bars at the top and bottom). These bars are also visible when shown on a regular 4: 3 TV.

Anamorphic

the widescreen picture is transferred to DVD in such a way that it fills the entire 4: 3 space. Thus, a similar picture on the DVD itself looks exactly like a frame of anamorphic film – elongated faces and emaciated things.

Final Result on the TV

At the same time, the final result on the TV depends on the following things:

  1. The mode set on the player itself
  2. Type of TV (16: 9 or 4: 3)
  3. The presence of a widescreen viewing function (16: 9) on a regular 4: 3 TV.

The model can be set on the player itself. Widescreen or letterbox (depending on the manufacturer, these modes may be called differently on different players).
If the widescreen mode is set, then on the TV

  1. 4: 3 – elongated faces
  2. 16: 9 – correctly proportioned image
  3. 4: 3 (with the 16: 9 function – the function is disabled) – elongated faces
  4. 4: 3 (with the 16: 9 function – the function is enabled) – correctly proportioned image (black bars on top and below).

What is it for in the latter case?

In fact, this feature is a common vertical screen change. That anyone would see on older types of TVs when they turned the control knob themselves.

The focusing of the beam was changed so that the entire image was shown only in the central part. And at the same time, the faces became flat and pan-shaped. In this case, this mode allows you to display the anamorphic image in the correct proportion on one side, and with the highest vertical resolution on the other (x480).
If the letterbox mode is set, then depending on the type of player and manufacturer, the letterbox filter starts to perform one of two operations:

  1. for cheap and simple players, it simply subtracts every fourth television line from the image, and the image takes on the correct proportions by reducing the vertical resolution by 25%
  2. for expensive and complex players , this filter begins to perform complex mathematical operations with the image, essentially trying to do this the same thing – create 3 from 4 lines.
    However, depending on the type of process – subtraction or transformation – the quality differs markedly.

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