This page will contain images about Topaz, as they become available.

Topaz

This article is about the mineral or gemstone, for other uses see: Topaz (disambiguation).

Topaz 4 Carat Oval Shape Topaz Gemstone Ring Enhanced with Azotic(r)Treatment Heart Cut Sky Blue Topaz Ring

The mineral topaz is a silicate of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It crystallizes in the orthorhombic system and its crystals are mostly prismatic terminated by pyramidal and other faces, the basal pinacoid often being present. It has an easy and perfect basal cleavage and so gemstones or other fine specimens should be handled with care to avoid developing cleavage flaws. The fracture is conchoidal to uneven. Topaz has a hardness of 8, a specific gravity of 3.4-3.6, and a vitreous lustre. Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw-yellow. They may also be white, gray, green, blue, or reddish-yellow and transparent or translucent. When heated, yellow topaz often becomes reddish-pink. It can also be irradiated, turning the stone a light and distinctive shade of blue. A recent trend in jewelry is the manufacture of topaz specimens that display iridescent colors, by applying a thin layer of titanium oxide via physical vapor deposition.

Topaz is found associated with the more acid rocks of the granite and rhyolite type and may be found with fluorite and cassiterite. It can be found in the Ural and Ilmen mountains, Czech Republic, Saxony, Norway, Sweden, Japan, Brazil, Mexico, and the United States.

Etymology and historical/mythical usage

The name "topaz" is derived from the Greek topazos, "to seek," which was the name of an island in the Red Sea that was difficult to find and from which a yellow stone (now believed to be a yellowish olivine) was mined in ancient times. In the Middle Ages the name topaz was used to refer to any yellow gemstone, but now the name is only properly applied to the silicate described above.

According to Rebbenu Bachya, the word "Leshem" in the verse Exodus 28:19 means "Topaz" and was the stone on the Ephod representing the tribe of Dan.

Topaz is also the birthstone of November.

Example of Heat Treated Topaz-Pink Topaz Pear Cut Ring

References

  • Webmineral
  • Mindat with location data
  • Mineral galleries

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Topaz is also the birthstone of November. See articles Stereoscopy and 3-D film. According to Rebbenu Bachya, the word "Leshem" in the verse Exodus 28:19 means "Topaz" and was the stone on the Ephod representing the tribe of Dan. The first commercially available HD players are expected to debut at the 2006 NAB Show in Las Vegas in April. In the Middle Ages the name topaz was used to refer to any yellow gemstone, but now the name is only properly applied to the silicate described above. New HD DVD and HD Blu-ray disks will greatly improve the 3D effect, in color coded stereo programs. The name "topaz" is derived from the Greek topazos, "to seek," which was the name of an island in the Red Sea that was difficult to find and from which a yellow stone (now believed to be a yellowish olivine) was mined in ancient times. Simple Red/Cyan plastic glasses provide the means to view the images discreetly to form a stereoscopic view of the content.

It can be found in the Ural and Ilmen mountains, Czech Republic, Saxony, Norway, Sweden, Japan, Brazil, Mexico, and the United States. This left and right layer technique is occasionally used for network broadcast, or recent "anaglyph" releases of 3D movies on DVD. Topaz is found associated with the more acid rocks of the granite and rhyolite type and may be found with fluorite and cassiterite. Stereoscopic video requires either two channels — a right channel for the right eye and a left channel for the left eye or two overlayed color coded layers. A recent trend in jewelry is the manufacture of topaz specimens that display iridescent colors, by applying a thin layer of titanium oxide via physical vapor deposition. in videoconferencing delivered on channels of fixed bandwidth, a constant bit rate (CBR) must be used. It can also be irradiated, turning the stone a light and distinctive shade of blue. For real-time and non-buffered video streaming when the available bandwidth is fixed, e.g.

When heated, yellow topaz often becomes reddish-pink. On fast motion scenes, a variable bit rate uses more bits than it does on slow motion scenes of similar duration yet achieves a consistent visual quality. They may also be white, gray, green, blue, or reddish-yellow and transparent or translucent. Variable bit rate (VBR) is a strategy to maximize the visual video quality and minimize the bit rate. Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw-yellow. HDTV has a still higher quality, with a bit rate of 10 Mbit/s. Topaz has a hardness of 8, a specific gravity of 3.4-3.6, and a vitreous lustre. For example, VHS, with a bit rate of about 1 Mbit/s, is lower quality than DVD, with a bit rate of about 5 Mbit/s.

The fracture is conchoidal to uneven. A higher bit rate allows better video quality. It has an easy and perfect basal cleavage and so gemstones or other fine specimens should be handled with care to avoid developing cleavage flaws. It is quantified using the bit per second (bit/s) unit or Megabits per second (Mbit/s). It crystallizes in the orthorhombic system and its crystals are mostly prismatic terminated by pyramidal and other faces, the basal pinacoid often being present. Bit rate is a measure of the rate of information content in a video stream. The mineral topaz is a silicate of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. The most common modern standards are MPEG-2, used for DVD and satellite television, and MPEG-4, used for home video.

This article is about the mineral or gemstone, for other uses see: Topaz (disambiguation).. Likewise, temporal redundancy can be reduced by registering differences between frames; this task is known as interframe compression, including motion compensation and other techniques. Mineral galleries. Broadly speaking, spatial redundancy is reduced by registering differences between parts of a single frame; this task is known as intraframe compression and is closely related to image compression. Mindat with location data. Video data contains spatial and temporal redundancy, making uncompressed video streams extremely inefficient. Webmineral. A wide variety of methods are used to compress video streams.

The expert then rates the impaired video using a scale ranging from "impairments are imperceptible" to "impairments are very annoying". In DSIS, each expert views an unimpaired reference video followed by an impaired version of the same video. One of the standardized method is the Double Stimulus Impairment Scale (DSIS). Many subjective video quality methods are described in the ITU-T recommendation BT.500.

The subjective video quality of a video processing system may be evaluated as follows:. Video quality can be measured with formal metrics like PSNR or with subjective video quality using expert observation. 4:4:4, 4:2:2, 4:2:0). A common way to reduce the number of bits per pixel in digital video is by chroma subsampling (e.g.

The number of distinct colours that can be represented by a pixel depends on the number of bits per pixel (bpp). It corresponds closely to the YUV scheme used in PAL television and the YDbDr scheme used by SÉCAM television. YIQ is used in NTSC television. Color model name describes the video color representation.

Pixels on computer monitors are usually square, but pixels used in digital video have non-square aspect ratios, such as those used in the PAL and NTSC variants of the CCIR 601 digital video standard, and the corresponding anamorphic widescreen formats. The aspect ratio of a full 35 mm film frame with soundtrack (also known as "Academy standard") is around 1.37:1. High definition televisions use an aspect ratio of 16:9, or about 1.78:1. The screen aspect ratio of a traditional television screen is 4:3, or 1.33:1.

Aspect ratio describes the dimensions of video screens and video picture elements. For example 512×512×512 voxels resolution, now used for simple 3D-video, can be displayed even on some PDAs. Video resolution for 3D-video is measured in voxels (volume picture element, representing a value in three dimensional space). 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.

New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, i.e. Standard-definition television (SDTV) is specified as 640×480i60 for NTSC and 720×576i50 for PAL or SÉCAM resolution. The size of a video image is measured in pixels for digital video or horizontal scan lines for analog video. Deinterlacing inevitably decreases video quality.

A procedure known as deinterlacing can be used for converting an interlaced stream, such as analog, DVD, or satellite, to be processed by progressive scan devices, such as TFT TV-sets, projectors, and plasma panels. The result is a much higher perceived resolution. In progressive scan systems, each frame includes all of the scan lines. For example, PAL video format is often specified as 576i50, where 576 indicates the horizontal resolution, i indicates interlacing, and 50 indicates 50 (single-field) frames per second.

Abbreviated video resolution specifications often include an i to indicate interlacing. NTSC, PAL and SECAM are interlaced formats. The horizontal scan lines of each interlaced frame are numbered consecutively and partitioned into two fields: the odd field consisting of the odd-numbered lines and the even field consisting of the even-numbered lines. Interlacing was invented as a way to achieve good visual quality within the limitations of a narrow bandwidth.

Video can be interlaced or progressive. To achieve the illusion of a moving image, the minimum frame rate is about ten frames per second. PAL (Europe, Asia, Australia, etc.) and SECAM (France, Russia, parts of Africa etc.) standards specify 25 fps, while NTSC (USA, Canada, Japan, etc.) specifies 30 fps. Frame rate, the number of still pictures per unit of time of video, ranges from six or eight frames per second (fps) for old mechanical cameras to 120 or more frames per second for new professional cameras.

In the UK, the term video is often used informally to refer to both video recorders and video cassettes; the meaning is normally clear from the context. The format of 3D-video is fixed in MPEG-4 Part 16 Animation Framework eXtension (AFX). Six or eight cameras with realtime depth measurement are typically used to capture 3D-video streams. 3D-video, digital video in three dimensions, premiered at the end of 20th century.

(See List of digital television deployments by country.). Digital television (DTV) is a relatively recent format with higher quality than earlier television formats and has become a standard for television video. Quality of video essentially depends on the capturing method and storage used. Video can be recorded and transmitted in various physical media: in celluloid film when recorded by mechanical cameras, in PAL or NTSC electric signals when recorded by video cameras, or in MPEG-4 or DV digital media when recorded by digital cameras.

The term video (from the Latin for "I see") commonly refers to several storage formats for moving pictures: digital video formats, including DVD, QuickTime, and MPEG-4; and analog videotapes, including VHS and Betamax. . Video is the technology of capturing, recording, processing, transmitting, and reconstructing moving pictures, typically using celluloid film, electronic signals, or digital media. Calculate the average marks for each HRC based on the experts' ratings.

Carry out testing. Invite a sufficient number of experts, preferably not fewer than 15. Choose a test method for how to present video sequences to experts and to collect their ratings. Choose the settings of the system to evaluate (the HRC).

Choose the video sequences (the SRC) to use for testing.

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