Screens PDF

Enter the characters you see below Sorry, we just need to make sure you’re not a robot. Enter the characters you see below Sorry, we just need to make sure you’re not a robot. Jump to navigation Jump to search This article is about the graphic technique. For screens PDF musical interval, see semitone.

Depuis trois jours Robin Reynart est sans nouvelles de son fils. C’est un père en quête de réponses et d’empathie.

Il s’interroge sur les causes de l’altercation qui a provoqué le départ du jeune homme. Qu’aurions-nous fait à sa place ? Laissé Baptiste s’abrutir des nuits entières devant l’écran ?

Comment en arrive-t-on là, aux mains avec son gamin ?

Le père évoque sa relation à un fils de plus en plus étranger, à un ado qui, entre addiction et détachement, se construit dans des relations virtuelles.

Mais ce père qui cause comme un boss, entre tablette et oreillette, ne trouve comme remède à sa propre solitude que la présence virtuelle de ses milliers d’amis chinois.

Ainsi, paroles du père, paroles du fils interrogent un quotidien envahi par les écrans et nous renvoient la balle.


D’abord éditrice puis professeur de français, Sarah Carré écrit aujourd’hui pour le théâtre. Elle anime aussi des ateliers d’écriture et des sessions de formation en écriture professionnelle.

For the musical note, see half note. Right: How the human eye would see this sort of arrangement from a sufficient distance. Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect. William Fox Talbot is credited with the idea of halftone printing. In an 1852 patent he suggested using « photographic screens or veils » in connection with a photographic intaglio process.

Several different kinds of screens were proposed during the following decades. One of the well known attempts was by Stephen H. Horgan while working for the New York Daily Graphic. The first printed photograph was an image of Steinway Hall in Manhattan published on December 2, 1873. The first truly successful commercial method was patented by Frederic Ives of Philadelphia in 1881.

Shortly afterwards, Ives, this time in collaboration with Louis and Max Levy, improved the process further with the invention and commercial production of quality cross-lined screens. The relief halftone process proved almost immediately to be a success. The use of halftone blocks in popular journals became regular during the early 1890s. The development of halftone printing methods for lithography appears to have followed a largely independent path. The most common method of creating screens—amplitude modulation—produces a regular grid of dots that vary in size. The other method of creating screens—frequency modulation—is used in a process also known as stochastic screening. This is the number of lines of dots in one inch, measured parallel with the screen’s angle.

The higher the pixel resolution of a source file, the greater the detail that can be reproduced. However, such increase also requires a corresponding increase in screen ruling or the output will suffer from posterization. Therefore, file resolution is matched to the output resolution. Three examples of modern color halftoning with CMYK separations.

When different screens are combined, a number of distracting visual effects can occur, including the edges being overly emphasized, as well as a moiré pattern. This problem can be reduced by rotating the screens in relation to each other. Halftoning is also commonly used for printing color pictures. In this case there is an additional problem that can occur. In the simple case, one could create a halftone using the same techniques used for printing shades of grey, but in this case the different printing colors have to remain physically close to each other to fool the eye into thinking they are a single color. To do this the industry has standardized on a set of known angles, which result in the dots forming into small circles or rosettes.

The dots cannot easily be seen by the naked eye, but can be discerned through a microscope or a magnifying glass. Though round dots are the most commonly used, there are different dot types available, each of them having their own characteristics. They can be used simultaneously to avoid the moiré effect. Generally, the preferred dot shape is also dependent on the printing method or the printing plate.

Round dots: most common, suitable for light images, especially for skin tones. Elliptical dots: appropriate for images with many objects. Square dots: best for detailed images, not recommended for skin tones. The transition between the square dots can sometimes be visible to the human eye. Digital halftoning has been replacing photographic halftoning since the 1970s when « electronic dot generators » were developed for the film recorder units linked to color drum scanners made by companies such as Crosfield Electronics, Hell and Linotype-Paul.

In the 1980s, halftoning became available in the new generation of imagesetter film and paper recorders that had been developed from earlier « laser typesetters ». Unlike pure scanners or pure typesetters, imagesetters could generate all the elements in a page including type, photographs and other graphic objects. Early laser printers from the late 1970s onward could also generate halftones but their original 300 dpi resolution limited the screen ruling to about 65 lpi. This was improved as higher resolutions of 600 dpi and above, and dithering techniques, were introduced. In photographic halftoning, the low frequency attribute is a local area of the output image designated a halftone cell. Within each cell, the high frequency attribute is a centered variable-sized halftone dot composed of ink or toner.