Page orientation
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Page orientation is the way in which a rectangular page is oriented for normal viewing. The two most common types of orientation are portrait and landscape. Portrait orientation is where the height of the page is greater than the width, and is more common for the pages of books. Landscape orientation, where the width of the page is greater than the height, is often used for images and diagrams that need to be wider than a portrait page.
Page orientation is also used to describe the dimensions of a video display. The most common video display orientation is landscape mode, specifically known as the 4:3 ratio which is 4 units wide and 3 units tall, and the more recent 16:9 widescreen landscape display mode.
Portrait screen orientation does exist for computers, but is not in popular usage. Portrait is preferred for editing page-layout work in order to view the entire page on the screen at once without wasted space along the sides.
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[edit] History
[edit] Orientation of Computer Displays
Portrait mode was first used on the Xerox Alto computer, which was considered technologically well ahead of its time when the system was first developed. Xerox product marketers did not understand how revolutionary the system was, and the portrait display faded away while common landscape-display televisions were appropriated for use as an inexpensive early microcomputer display.
When the Macintosh computer was introduced, WYSIWYG page layout using Aldus PageMaker became popular. The Macintosh rekindled interest in portrait displays, and the first portrait displays for it were developed by Radius Corporation.
For the first computing devices a screen was built to operate in only portrait or landscape mode, and changing between orientations was not possible. Typically a custom video controller board was needed to support the unusual screen orientation, and software often needed to be custom-written in order to support the tall, narrow screen layout.
As video display technology advanced, eventually the video display board was able to accommodate rotation of the display and a variety of differing resolutions and scan rates. After several years of producing the first Macintosh portrait display, Radius introduced the Radius Pivot CRT monitor, that could be freely rotated between landscape and portrait with automatic orentation changes done by the video controller.
Rotation is now a common feature of modern video cards but is typically rarely used.
[edit] Orientation of Video Game Displays
Portrait mode is popular with arcade games that involve a vertically oriented playing area, such as Pac Man and Donkey Kong. The vertical orientation allows greater detail along the vertical axis while conserving detail on the sides.
The conversion of early popular arcade games to home consoles was difficult not only because the home computing capability was lower, but also the screen orientation was wrong and the home user could not be expected to set their television on its side to show the game correctly. This is why most early home versions of arcade games have a wide, squashed appearance compared to the full-quality arcade versions.
Modern arcade emulators are able to handle this difference in screen orientation by dynamically changing the screen resolution to allow the portrait oriented game to resize and fit a landscape display, showing wide empty black bars on the sides of the portrait-on-landscape screen.
[edit] Modern display rotation methods
Many modern video cards offer digital screen rotation capabilities. But in order for it to be used correctly, a special rotating display is required that is designed to be pivoted.
[edit] Rotation of CRT monitors
Very few CRT monitors made today are designed to permit rotation into portrait mode. It is not wise to turn a standard CRT monitor or television on its side due to a number of technical issues:
- The cooling vents are normally designed for natural air convection flow from bottom to top; turning the case sideways can lead to unintended heat buildup and component failure.
- The typical CRT monitor plastic case is not designed to sit stably when turned sideways without a custom-made supporting stand.
- The weight of a large CRT is typically meant to bear on the base frame. A plastic case may flex or crack if the CRT weight is supported only by the thin plastic surround.
[edit] Magnetic effects on rotated color CRTs
Due to effects of the Earth's magnetic field on the CRT shadow mask, a CRT turned on its side will have the colors skewed and needs to be degaussed in the portrait orientation for the colors to be correct. In step two of this example image, the bottom left colors appear to be correct, but in fact blue has been swapped with red, red swapped with green, and green swapped with blue. After degaussing the colors are corrected and uniform across the entire screen.
Upon being returned to normal landscape mode, the colors skew in the opposite direction and remain that way until the screen is again degaussed in landscape orientation.
These magnetic anomalies do not affect purely monochrome CRT displays.
[edit] Rotation of LCD monitors
Rotation of LCD monitors is easier and less complicated to do since the mass of the panel is low, the heat generated is low, and there are no magnetic effects to be concerned about. Many higher quality panels feature built in pivot points to allow the user to easily rotate the screen into portrait mode.
However, due to the light polarization technology an LCD monitor, the angle of image viewability will degrade when rotated. Liquid crystal displays vary in contrast when viewed from different angles along one axis. This axis is normally oriented to be vertical so that the image quality appears unchanged when the screen is viewed from the side, and image contrast is adjusted by tilting the panel up or down. By rotating the screen 90 degrees, the varying contrast axis is now horizontal and a viewer to one side will see a washed out light contrast image, while a viewer on the other side sees a very dark contrast image.
[edit] Rotation of projectors
Projectors can generally operate from any angle due to the compact, rigid design and a cooling system utilizing a forced-air fan. However for large heavy projectors the problem is how to mount the projector sideways, since nearly all ceiling mounts assume the projector hangs down from the mount in an upside-down landscape position. Extra-heavy bracing or weighted counter-balancing may be required to support a projector in a sideways portrait orientation.
[edit] External links
- Study from Pivot Software (PDF)
- The perfect portrait (blog post at perton.com)
