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a
guide to printing & file types
The
following information is intended and a basic overview of the printing
process and a brief description about each type of file listed. This is
not an absolute guide. If you have any specific concerns, please be sure
to talk to your printer about them, as different equipment and its usage
could result in varied outcomes.
file
resolution printing
fonts
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pdf
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jpg
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EPS
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Photoshop
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tif
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Quark
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gif
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file
resolution
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An image file's resolution refers to it's clarity. For printing,
an image file must be at least 300dpi (dots per inch) at 100%
size. Resolution and size have a direct relationship. While
an image's size and resolution can be manipulated, one has
a direct impact on the other, much like the action of a seesaw
or a balance scale.
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In
the chart above, A represents an ideal set up. The image
used has a resolution of 300 dpi and it is being used at 100% size.
In B, that same image has been decreased in size. The direct
resolution-to-size relationship pushes the resolution up to 620
dpi. It is not necessary to have a file over 300 dpi, but it doesn't
hurt. In situation C is where the problem resides. Once that
same image's size is increased over 100%, it begins to drop in resolution,
thus becoming more and more blurry. Although it may appear clear
on a computer monitor or even from a small office printer, once
it is on the printing press it will be very blurry. This
is why it is not always an option to increase the size of a given
photograph or graphic element.
NOTE:
Just about every image on the internet, graphic and photographic,
is a low-res jpg
or a gif, which
are both unuseable for print work.
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printing:
processes, colors and paper
There
are two different kinds of color systems. Four Color Process and
Spot Color.
Four
Color Process is four colors of ink dotted onto the paper to create
all the necessary colors on the piece that is being printed. The
colors used are cyan (C) ,
magenta (M) , yellow (Y)
and black (K) .
This type of printing, known as "process" or "CMYK",
is the most common as it is the least expensive. One drawback to
printing CMYK is that there are some colors that cannot be achieved.
For these colors (such as bright oranges, blues and any metallic
colors) you must use a spot color.
Spot
colors are used primarily when a color must be exactly the same
all the time (such as when printing a company logo) or when a desired
color cannot be obtained with a four color process. All spot colors
are assigned numbers by the manufacturer. Pantone®
Inc has created The Pantone Matching System®
(PMS) which, for example, is where colors like PMS 187 get their
names. There are other manufacturers of colors, such as Toyo Ink,
however the most widely used colors are in The Pantone Matching
System®;
it is the industry standard.
These
two printing processes can be combined to create what is usually
referred to as a "five-color-job" or "six-color-job".
In this case, the four color process is used for most of the printing
but there are areas where PMS color(s) are added to the job. Vast
combinations and variations of these two processes can be set up.
There
are several options on how to achieve the desired shine on a printed
piece.
Different
types of paper produce different results. Matte paper will not shine
much versus coated paper, which will. Papers can be coated on one
or two sides. This is where you get the term C1S or C2S (Coated
One Side / Coated Two Side). Keep in mind that writing on a coated
stock is difficult, so items such as postcards are generally printed
on C1S, so that you can write on the mailing side, but the photo
side still has a nice shine. You would not want to have anything
that people need to write on printed on a coated stock.
In
addition to the paper, there are processes that the printer can
go through to add shine and luster. 1) Spot Varnish. This is a varnish
that is layed down on certain parts of the piece to help make things
jump out. It is considered a spot color when printing. 2) Aqueous
Coating. This is an overall coating that is usually done to make
the piece have a shine. It's not considered a color, rather as a
finish. Most printers will do this at no additional charge. 3) UV
Coating. This makes an extreme shine. This is a very special process
that cannot be done by the printer. Your piece will need to be printed,
then shipped to a UV house for this treatment. The results are undeniably
outstanding, but the process can be quite costly.
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TYPES
OF FILES:
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adobe pdf (Adobe Acrobat®
portable document format)
This
very common file is mainly used to make printable text forms. As
far as in a graphic arts arena, a pdf file is great for proofing
text and positioning. However, when viewing the pdf of a design
layout it is not uncommon for fonts to not load correctly, for there
to be spacing issues or for images to appear low quality, all of
which may not be a problem in your actual design file. In some rare
cases, graphic elements from a pdf file can be extracted and used,
but usually a pdf is too low resolution to use for print work.
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jpg
or jpeg (compressed image file)
Another
very common file. A jpg is a highly compressed image file. A jpg
is a file that has the capability while compressed, to hold the
information to create millions of colors when uncompressed. They
can be created as "high-res" or "low-res" jpg
files. High-res jpg files can be uncompressed to be significantly
larger than their compressed size. Low-res jpg files, the more common
jpg, cannot be expanded to much larger than it's original size (100%).
Because jpg's have such a good compression, they are widely used
to display photos for screen applications (internet use). Usually
these files are no more than 72 dpi, which is far too low for printing.
When these 72 dpi jpg's are brought up to 300 dpi, they are usually
far too small to use.
NOTE:
while a jpg can hold the color information for a CMYK file, most
jpgs are RGB and will need to be converted to CMYK before going
to press. Conversly, a jpg left in CMYK mode will not display on
screen.
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eps
(encapsulated post script)
This
is a special type of file. It can be created and opened in many
types of programs (Adobe Illustrator®,
Adobe Photoshop®, Quark Xpress®
and more). What makes an EPS special is that is has the capability
to contain vectored art. Vectored art means that it does not contain
a resolution. It can be shrunk and/or expanded to any size without
having to worry about it becoming blurry. That doesn't mean that
all EPS files are or can be vectored! Only line art can be vectored
art and it must be CREATED as vectored art. You cannot vector a
photograph, any other types of images or an existing non-vectored
line art. Only line art, logos and things of that nature can be
vectored and only when they are originally created.
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psd
(Adobe Photoshop®
document)
This
file can only be opened in Adobe Photoshop®.
This is a popular program to create backgrounds and complicated
graphics. The most noteable feature of a Photoshop®
file is that it supports layers. A layered file is essential when
attempting to re-arrange art that has been created by someone else
(like when using one package's art to create another package). With
a layered file, you can move parts of an file around to fit your
needs. However, a Photoshop® file is not
always useable. It is possible to flatten a Photoshop®
file, which makes it impossible to move the graphic elements.
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tif
or tiff
(non-compressed image file)
A
tif is an image file that does not allow compression. This type
of file is the preferred format when designing and when going to
print. This file accurately supports CMYK (unlike a jpg, which is
RGB or a gif, which the color is indexed). Just like any other image
file, a tif's resolution is variable. So for printing, following
the same seesaw rule as stated above, a tif should be 300 dpi at
100% size. It is possible to create low-res tifs, which would be
just as unuseable as any other low-res image file.
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qxd
(Quark XPress document)
Quark
XPress is a layout program. It allows the designer to put graphic
elements and typed text together and easily manipulate their position,
size, etc. However, a Quark file is only a container that displays
the fonts and images in the manner that you tell it. For example,
when you insert an image, it does not embed the image into itself
(like in Word), it only creates a window for the image to be displayed
in and links it to the Quark file. Therefore, you must have that
image when passing this Quark file along to someone else or for
printing. The same rule applies for the fonts. After typing in text,
Quark looks for the font file so that it knows how to display the
text you just typed in. A common mistake is to build a layout in
Quark and then simply give that file to someone else. You must "collect
for output", which means gathering all of the fonts and images
used in that Quark file, preferrably placing them in folders labelled
"fonts" and a folder labelled "images".
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gif
(indexed color image file)
A
gif is an image file. It is an extremely condensed file that contains
very limited colors. A gif contains anywhere from two to 256 colors.
These are the 256 "web-safe" colors. Unlike a jpg, which
contains millions of colors and compression information, a gif cannot
be expanded or converted to anything useable for print work. A gif
file is primarily used to display on screen (as on a website), since
it supports a transparent background and animation.
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fonts
Fonts
are bitmapped files that create differently shaped letters and numbers.
Some fonts are common and some fonts are not. When designing a piece,
usually several fonts are used. When transferring your layout file,
no matter what program it is in, you must also send along the fonts
used in that piece. The reason is that if the next person does not
have that particular font, the job cannot be printed correctly,
it will have "missing font(s)". It is possible to replace
missing fonts with others that are similar in appearance, but the
new designer would need to see what the font looks like to get a
close match. In this case a print from the original designer would
be needed. When transferring the layout file, even the most common
fonts, like Arial, Helvetica, etc., should be included. The reason
for this is that one person's Helvetica may be slightly different
than another person's Helvetica, which could cause shifting in position
of text or images.
Damaged
fonts are treated the same way as missing fonts. Font files are
small and easily damaged when being transfered. Going from one person's
machine to a disk, then to another machine, then maybe to a server,
then back to a disk... well you get the picture.
There
is also the issue of MAC fonts and PC fonts. While there are a lot
of fonts with the same names for both platforms, fonts from a MAC
cannot be used on a PC and fonts from a PC cannot be used on a MAC.
They are two completely different types of files.
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