This format reduces file size by removing image information lossy compression.. Click the Save In Win or Where Mac list arrow, and then select a location in which to save the file.. Cha
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Reducing the size of a photograph presents its own particular set of problems, and Photoshop comes to the rescue with solutions For pho-tographic images, the best format to use is the JPEG (Joint
Photographic Experts Group) format This format reduces file size by removing image information (lossy compression) For example, a 1 MB uncompressed TIFF file can be reduced to 20 KB or 30 KB using JPEG compression That reduces the download time of the image on a 33 KB modem from15 minutes to 10 seconds While that is quite a reduction, it also means most of the image colors have been removed and the remaining colors are dithered (simulated) to fool the eyes into seeing colors that are no longer in the image Highly compressed JPEG images look good on a monitor, but fare poorly when sent to a printer If you’re working with a 16-bit document, you can save it in the JPEG format (8-bit) using the Save As command without having to change the bit depth before hand (New !)
Preparing a
Photograph for
the Web
Prepare a Photograph for
the Web
Open a photographic document
Click the File menu, and then click
Save As.
Enter a name for the file in the
Save As box
Click the Save In (Win) or Where
(Mac) list arrow, and then select a
location in which to save the file
Click the Format list arrow, and
then click JPEG.
Click Save.
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From the Library of Wow! eBook
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Select from the following JPEG
Options:
◆ Matte The JPEG format does
not support transparency Click
the Matte list arrow, and then
select the color with which to
fill transparent areas within the
active document
◆ Quality The Quality option
determines the amount of image
information loss Enter a value
from 1 to 12; the higher the
value, the more information is
retained, thus creating a larger
file
◆ Baseline (Standard) The format
is recognized by most browsers
◆ Baseline Optimized Produces
optimized color, and a slightly
smaller file size, but is not
supported by older browsers
◆ Progressive Displays a series
of increasingly detailed scans
as the image downloads The
visual impression is of a blurred
image slowly coming into focus
(not supported by older
browsers)
◆ Scans If Progressive is
selected, select the number of
scan passes for the image
Click OK.
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Using the JPEG 2000 Format
JPEG 2000 is a file format that provides more options and greater flexibility than the standard JPEG format It produces images with better compression and quality for both web and print publishing
The optional JPEG 2000 format plug-in can be found on the Photoshop CS5 installation CD in Goodies/Optional Plug-Ins/Photoshop Only/File Formats Currently, only computers with the necessary plug-in can view a JPEG 2000 file on the Web
For Your Information
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Images saved for press printing are in another world For example, images displayed on a monitor use the RGB (additive) color space, while images sent to a press use the CMYK (subtractive) color space
The format of choice is the DCS (Desktop Color Separations) format
The DCS format is a version of the standard EPS format that lets you save color separations of CMYK images DCS comes in two flavors, DCS 1.0 and DCS 2.0 Both create five separate files: one is for each of the four color plates, Cyan, Magenta, Yellow, and Black, and one is for
a combined, or composite image However, the DCS 2.0 format allows you to save alpha and spot-color channels, as well as giving you the option of saving the five separate files under one combined file name
You can also use the DCS 2.0 format to export images containing spot channels It's important to understand that the only device that can print a DCS file is a PostScript printer As with anything related to press operations, always contact your friendly press operator and ask what format to use
Preparing an Image
for the Press
Prepare an Image for
the Press
Open a document
Click the File menu, and then click
Save As.
IMPORTANT Images saved in
the DCS format must be in the
CMYK color mode
Enter a name for the file in the
Save As box
Click the Save In (Win) or Where
(Mac) list arrow, and then select a
location in which to save the file
Click the Format list arrow, and
then click Photoshop DCS 2.0.
Click Save.
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Select from the following DCS 2.0
Format options:
◆ Preview Click the list arrow,
and then select what type of
low-resolution image to use in
the layout application
◆ DCS Click the list arrow, and
then select how you want the
color plate information saved
◆ Encoding Click the list arrow,
and then select how the image
data is encoded for delivery to
the output device (contact your
service bureau)
◆ Include Halftone Screen Select
the check box to include any
halftone screens
◆ Include Transfer Function Used
with high-end commercial
production jobs
◆ Include Vector Data Select the
check box to include any vector
data contained within the active
image
◆ Image Interpolation Select the
check box to create an
anti-aliased version of the Preview
image (does not impact
printing)
Click OK.
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While not everyone has access to a 4-color press, even casual com-puter users have or have access to, an inkjet or laser printer Inkjet and laser printers apply color to the paper using dots of ink In fact, one of the measurements of quality for this type of output is its printing resolu-tion For example, a photo-quality inkjet or laser printer can have a res-olution of 1,400 dpi and higher, or one thousand four hundred dots of color information per linear inch There are several file format options
to print this type of output; however, none is as versatile as the TIFF for-mat The Tagged-Image File Format uses lossy or lossless compression, and lets you save multiple Photoshop layers, as well as alpha channel information In addition, there is hardly a layout application in the mar-ketplace, Macintosh or Windows, that will not open an image saved in the TIFF format
Preparing an Image
for an Inkjet or
Laser Printer
Prepare an Image for an Inkjet
or Laser Printer
Open a document
Click the File menu, and then click
Save As.
Enter a name for the file in the
Save As box
Click the Save In (Win) or Where
(Mac) list arrow, and then select a
location in which to save the file
Click the Format list arrow, and
then click TIFF.
Click Save.
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Select from the following TIFF
Options:
◆ None No compression is
performed to the image
◆ LZW Performs lossless
compression to the image
When this method is used, the
receiving application must have
the corresponding LZW option
or it will not be able to
decompress the file
◆ Zip Performs a standard Zip
(lossless) compression to the
image Receiving application
must have an unzip utility
◆ JPEG Performs lossy (image
loss) compression to the image
◆ IBM PC Select PC if the image
is to be used on an IBM system
Works also on Macintosh
systems
◆ Macintosh Select Macintosh if
the image is to be used on a
Macintosh system
◆ Save Image Pyramid Check to
save the image using several
image resolutions Lets you
decide what resolution to use
when reopening the image
◆ Save Transparency Check to
preserve any transparent areas
in the active image
◆ RLE Run Length Encoding (RLE)
helps to compress solid areas of
color across multiple layers
◆ ZIP Uses the Zip format to
compress multiple layers
◆ Discard Layers and Save a
Copy Creates a copy of the file
without the layers, essentially
saving a composite image file
Click OK.
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Getting the Best Results on an Inkjet or Laser Printer
Since your monitor displays an image using light and a desktop
print-er reproduces an image using inks, dyes, or pigments, it is impossi-ble for a desktop printer to reproduce all the colors that can be dis-played on a monitor However, by incorporating certain procedures (such as color management) into your workflow, you can achieve predictable results when printing your images to a desktop printer
For more information on getting the best color results, see Chapter
18, "Managing Color from Monitor to Print.”
For Your Information
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Remember that raster images are all about
resolution Images have a specific scanned
resolution (spi, samples per inch) Your
moni-tor also has a native resolution (ppi, pixels
per inch), as does output devices such as
inkjet printers (dpi, dots per inch), and
high-end presses (lpi, lines per inch) While all
these terms may seem a bit complicated,
they're not; they simply explain how much
information is contained within the image
Most computer monitors are set to a fixed
resolution of 72 or 96 ppi Say you scan a 4
by 4 inch image at 288 spi (that's 4 times the
resolution of a 72-ppi monitor) If you
attempted to display the image at 100% view,
the monitor would take the image pixels and
adjust the width and height to match its
reso-lution, so the image would be 16 by 16 inches
(288 divided by 72 = 4) If the display of the
image doesn’t fit the size of your monitor and
you attempt to reduce the magnification of
the image to make it fit the monitor size,
Photoshop will have to remove pixels from
the image to make it fit This typically causes
the image to generate jagged lines, especially
around angles The moral of this story is:
when adjusting an image for viewing on a
monitor (for example, when preparing a slide
presentation), never change the zoom of the
image to fit the monitor; always adjust the
resolution by selecting the Image menu, and
then clicking Image Size
When it comes to output, such as to an inkjet printer, the rules are a bit more forgiv-ing Many output devices have print resolu-tions of 1,440 or higher However, we're not talking about fixed monitor pixels (ppi), we're talking about dots of ink hitting a piece of paper (dpi) Most inkjet printers, because of the dot gain of the inks (that's the amount of space over which a dot of ink spreads when it hits the paper), do not need image resolution greater than 300 spi Although image quality suffers when you enlarge an image beyond its original size for viewing on a monitor, if you use higher resolutions than needed when you print, the image won't be degraded;
you'll just be printing an image with a larger file size However, that can be a waste of time For example, a 300 spi, 8 by 10 inch image will have a file size of about 20 MB;
the same image scanned at 1,200 spi will pro-duce a 329 MB file size When you print the two images, you will probably not notice any difference in quality; however, it will take, on average, 6 minutes longer to print the 1,200 spi document on most mid-range printers
The bottom line is that resolution repre-sents the amount of information contained within a linear inch; however, various devices handle that same resolution differently The good news is that understanding those differ-ences helps you to create a useable work-flow Knowledge is power
Understanding Monitor, Image, and Device Resolution
From the Library of Wow! eBook