Quelques unités utilisées en imprimerie

["Jean Fontaine" <jfontain@xxxxxxxxxxx>]

> > >Bon, j'avoue, j'ai donné un numéro au pif. Par curiosité, les
générations,
> > >vous calculez ça comment ?
> >
> > Pour moi c'est 20 ans. Mais je ne sais pas pourquoi.
>
> Personnellement, je monte à 30/35

Voici ce qu'en dit un dico Internet sur les unités de mesure :

generation (gen)
an informal unit of time. Roughly speaking, a generation is the average
length of time between the birth of a parent and the birth of the child.
This leaves a question, however: should just the father, or just the mother,
or both parents be included in the calculation? Various answers to this
question, plus a lack of consistent data, have led to a range of estimates
for the length of a generation, from about 25 to 35 years. Genealogists tend
to use the higher figures, anthropologists the lower ones. There is some
research suggesting that the approximate length of the generation in the
world today is about 28 years.

(Source : http://www.unc.edu/~rowlett/units/index.html )

Cet intéressant dico est consacré aux unités de mesures utilisées dans tous
les domaines. Pour ne pas oublier la charte, allez, voici quelques articles
traitant d'unités utilisées en imprimerie.

dpi
a unit used to measure the resolution, or sharpness, of a photograph or
video image. The unit, an abbreviation for "dots per inch," remains in use
even though individual picture elements are now called pixels rather than
dots.

ppi
abbreviation for pixels per inch. A pixel is a single "picture element", so
ppi measures the resolution, or fineness, of an image. The unit is identical
to dots per inch (dpi).

point (pt)
a unit of length used by typographers and printers. When printing was done
from hand-set metal type, one point represented the smallest element of type
that could be handled, roughly 1/64 inch. Eventually, the point was
standardized in Britain and America as exactly 0.013 837 inch, which is
about 0.35 mm (351.46 micrometers) and a little bit less than 1/72 inch. In
continental Europe, typographers traditionally used a slightly larger point
of 0.014 83 inch (roughly 1/67 inch), sometimes called a Didot point after
the French typographer Firmin Didot (1764-1836). The distinction between the
British and Didot points is rapidly disappearing, since most digital
typesetting and page design software now define the point to be exactly 1/72
inch (0.013 888 9 inch or 0.352 777 8 millimeters).

cicero
a unit of distance used by typesetters and printers in continental Europe,
equal to 12 Didot points. This is approximately 0.1780 inch or 4.52
millimeters. The cicero corresponds to the British and American pica.

pica (pi)
a unit of length used by typographers and printers. One pica equals 12
points, 4.22 mm, or a bit less than 1/6 inch. "Pica type" is type that sets
six lines to the inch. The origin of this word is not known. In the Catholic
Church, a "pica" is a book of daily services, so it is possible that pica
type got its name from being used to print picas. The unit is pronounced
"pike-ah."

em
a printer's unit of relative distance. One em is the height of the point
size being used. If 12 point type is being set, then one em is 12 points,
and so on. See point [2].

en
a printer's unit of relative distance, equal to 1/2 em. If 12 point type is
being set, then one en is 6 points.

agate
a traditional unit of distance used in printing. The agate is usually
considered equal to 1/14 inch (1.814 millimeters), since the traditional
type size called agate set 14 lines to the inch (very small print!). In the
more modern measuring system based on points [2], agate type has a height of
5.5 points; this would make the agate equal to about 0.076 inch or 1.933
millimeters.

milline
a traditional unit of advertising. One milline equals the width of a line of
"agate" type (5.5 points, or about 2 mm) times the width of a column times
one million copies of the publication.

column inch (col in)
a unit of relative area used in journalism. A column inch is an area one
column wide and one inch deep; it is often used to measure the length of
newspaper stories.

-mo
a "unit" traditionally used in printing to describe the page size of a book
or other publication. In traditional printing, large sheets are printed,
folded, and then cut to manufacture the book. After the cut is made, the
sheet has been divided into a certain number of "leaves." Each leaf, folded
at the spine of the book, comprises two pages front and back. When sheets
were cut to form 4, 8, or 12 leaves, the resulting pages were described as
quarto (4to), octavo (8vo) or duodecimo (12mo), respectively. Later, the
suffix -mo from duodecimo was made into a suffix which can be attached to
any number to indicate the number of leaves per sheet; thus 16mo indicates
16 leaves per sheet.

quire (qr)
a traditional unit of quantity used for counting sheets of paper. The word
is from Latin, meaning "by fours." A quire was originally comprised of 24
sheets cut from four of the large sheets produced by the paper maker. In
modern use a quire is often reckoned as 25 sheets, so that a ream of 20
quires is now 500 sheets rather than the traditional 480.

ream (rm)
a unit of quantity used for counting sheets of paper. The word is thought to
be derived from the Arabic rizmah, meaning a bundle. A ream is equal to 20
quires, which would be 480 sheets with the traditional definition of a quire
as 24 sheets. In recent years, however, the ream has been redefined to equal
500 sheets. (Working backwards, this changes the definition of a quire from
24 to 25 sheets.) The new definition reflects the current practice of
marketing many kinds of paper in packages of 500 sheets.

perfect ream
a unit of quantity for paper. An ordinary ream is 480 or 500 sheets; a
perfect ream is 516 sheets. The additional amount is to allow for sheets
which may be spoiled in shipment.

bundle (bdl)
a unit of quantity for paper, equal to 2 reams or 40 quires. This would be
960 sheets using the old definition of 24 sheets per quire, or 1000 sheets
using the newer quire of 25 sheets.

bale (bl)
a bound, rectangular package. The word "bale" has been used in many ways to
describe standard packages of various commodities. For example, a bale of
paper is traditionally equal to 10 reams. However, the bale is best known as
a commercial unit of weight formerly used to measure shipments of cotton. In
the United States, one bale was formerly equal to 500 pounds, but is now
usually 480 pounds. The British used the Egyptian bale, equal to 750 pounds.
Other countries use a variety of bale sizes. Link: statistical bale sizes
for various cotton-producing countries, from Cotton Outlook.

basis weight
a unit used in the paper industry to express the weight (really, the
thickness) of paper. The basis weight is the weight in pounds of one ream of
a "basic size" sheet. For bond paper, the traditional basic size is 17 x 22
inches.

pound weight (lb wt or lb)
a traditional unit measuring the weight or thickness of paper. Paper is
described as, say, 24 pound weight if one ream (500 sheets) cut 25 by 38
inches (63.50 by 96.52 centimeters) has a mass of 24 pounds.

arroba
a traditional unit of weight in Spain and Portugal, equal to 1/4 quintal.
However, the Spanish and Portuguese quintals are of different sizes. In
Spain, the arroba equals 25.36 pounds (11.50 kilograms); arrobas of very
similar sizes were established in the Spanish speaking countries of Latin
America. In Portugal and Brazil, the arroba equals 32.38 pounds (14.69
kilograms). The name of the unit comes from ar rub', Arabic for "the
quarter."

You are welcome to email the author (rowlett@xxxxxxxxxxxxx) with comments
and suggestions.

Voilà.

Jean Fontaine
jfontain@xxxxxxxxxxx