Specialized
Processes
Creating files for special uses often requires
special processing. These techniques are
fairly
elaborate, so the
short overviews here are
meant
for a clearer understanding of
possibilities. The creation of specialized formats for the
Internet, professional printing, or video requires a mastery of
several
interconnected
skills. Let's take a quick look at
converting to special purpose files.
Save For Web
Preparing images for the Web is all about
compromise. You must learn to balance appearance with file
size
. If
a Web page takes too long to load, people will leavewhich defeats
the purpose of running the site. Fortunately, Photoshop provides a
powerful command for compressing images and previewing the results:
the Save For Web command.
Video Training
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Save for
Web
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Let's give the Save For Web command a try:
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1.
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Open
the file Board.tif from the Chapter 17
folder on the DVD-ROM.
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2.
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Choose File > Save For Web.
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3.
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The Save For Web dialog box offers several
important options for optimization and preview:
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Toolbox:
If you can't see
the entire image, you can use the Zoom tool to make the image more
visible. Additionally, you can use the Hand tool (or hold down the
Spacebar) to drag and navigate around the image. Alternatively, you
can click the Zoom Level menu in the lower-left corner and choose a
magnification level.
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Optimization tabs:
By
clicking the four tabs at the top, you can choose to view the
Original image, an Optimized view, 2-Up to view two versions of the
image side by side, or 4-Up to view four versions of the image side
by side. Being able to compare optimized images helps choose the
right format and compression settings. In the case of this image,
choose 2-Up.
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Image Optimization
Info
:
The
area below each image in the Save For Web dialog box gives you
optimization information. You can see the current optimization
applied, the
projected
file size, and the estimated download time
based on a selected modem connection speed. Choose the JPEG High
preset and you'll notice that the file has been reduced from 17.3M
to 677K (a significant savings). However, the download time is 123
seconds on a 56K modem (you can right-click the time to choose
another speed).
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4.
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We need to further reduce the file size for
Internet delivery. The first area to tackle is the actual image
size in pixels. Click the Image Size tab and you'll see that the
image is almost 2,000 pixels wide (which is much wider than a
typical Web page). Type in a Height of 500 pixels, so the image can
integrate easily into our Web page (even with a screen resolution
of 800 x 600, a height of 500 would allow the image to display
without scrolling up and down). Click Apply to resize the
image.
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5.
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The file size has been significantly reduced,
but it's hard to see the effects of the compression. Set the image
magnification view to 100%.
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6.
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Change the amount of Compression by either
changing the preset (from High to Medium, for example) or adjusting
the Quality slider. You will need to release the slider for the
image to refresh. Try a setting of 45 to see the results, then
experiment with other
numbers
. The image is now at just over 20K.
This is more than a 99.9% reduction in file size and a fundamental
change for Web delivery.
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7.
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Towards the lower-right corner, you have the
ability to choose to preview the image in a Web browser. If you
don't see your browser of choice, just choose to Edit List.
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8.
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Click Save to process the image and save a
compressed Web-ready version. The original file will
remain
untouched, and its resolution and quality will be identical to its
state when you launched the Save For Web command.
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9.
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Experiment with other file formats such as GIF
and PNG to see their benefits and limitations.
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Convert to
CMYK
While CMYK conversion is an everyday process for
many users, several authors and
trainers
have developed some useful
techniques. What I offer here is a proper workflow that will work
for most users, on most images, in most environments. I
encourage
you to continue to explore prepress production through further
reading. CMYK conversion can be a very tricky process, and it is
essential that you have access to the
color
profile used by your
output device. With all of these caveats said, let's take a look at
the process:
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1.
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Check your color management settings by
choosing Edit > Color Settings or pressing Shift+Cmd+K
(Shift+Ctrl+K). Choose North America General Purpose 2.
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2.
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Open the file Bikers.tif from the Chapter 17
folder.
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3.
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Choose View >
Gamut
Warning or press
Shift+Cmd+Y (Shift+Ctrl+Y). Areas that are too bright or
saturated
for CMYK printing will be highlighted in gray. This is because the
RGB space can represent a wider ranger of visible colors based on
the additive method of color. CMYK printing instead uses the
subtractive
model, and it has a narrower range.
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4.
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Select the Sponge tool (O) from the Toolbox.
Adjust the brush to a large size with soft edges. Set the flow to a
lower value such as 20% and the mode to Desaturate. This will
gently soak up the color in the oversaturated areas.
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5.
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Carefully paint over the oversaturated areas
with the Sponge tool. It may take multiple strokes, but you'll see
the gamut warning go away. Repeat for other problem areas in the
photo.
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6.
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When all of the gamut warning has been
removed, choose Image > Mode > CMYK. There should be no
visible shifting in the colors.
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7.
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Save the image in a print-ready format such as
TIFF.
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Add an Alpha
Channel
We explored saving selections as channels much
earlier in the book (Chapter 5, "Selection Tools and Techniques").
The alpha channel can be used to store transparency information,
and it is particularly useful for video and multimedia users. If
you are using Photoshop CS2, there are new actions for the video
professional that I cowrote with Daniel Brown. These can speed up
certain
tasks
for a video workflow. Two of these actions can create
an alpha channel for
multilayered
graphics with transparency.
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1.
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Open the file NTSC Test Image.psd from the
Chapter 17 folder.
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2.
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Make sure the Alpha Test layer is visible and
others are turned off.
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3.
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Call up the Actions palette and load the Video
Actions by clicking the submenu. Choose the Video Actions set (you
must have CS2 or later to access them).
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4.
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Choose the Create Alpha Channels from Visible
Layers
action. You must see Photoshop's transparency grid for it to
work.
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5.
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Click the Play Selection button to run the
action. A dialog box comes up with instructions. Read it and click
Continue.
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6.
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A new alpha channel is added to the document.
Save the file as a PICT, TIFF, or Targa file and choose to embed
the transparency by including the alpha channel
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There are many other issues
related
to creating
graphics for use in video. I invite you to check out my reference
site, www.PhotoshopForVideo.com. You'll find free training movies
and links to my DVDs and other books for the video industry.
Include a Clipping
Path
If you are preparing an image to import into a
page layout program (such as Adobe InDesign or Quark Xpress), you
may want to embed a clipping path. The clipping path embeds the
transparency information into the file.
It's important to note that paths are
vector-based; therefore, they have hard edges (and do not preserve
softness or a feathered edge). Features like a drop shadow cannot
be preserved when creating a clipping path (but can often be added
in the page layout program). An alternative to clipping paths is to
use an alpha channel (which can include a feathered edge).
Photoshop offers a few ways to create accurate
clipping paths; we'll explore the
easiest
. Photoshop has a built-in
wizard to help with the creation of clipping paths:
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1.
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Open the file Ch17 Clipping Path.psd from the
Chapter 17 folder.
The Export Transparent Image Assistant only recognizes one layer,
so it is a good idea to have a little human intervention.
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2.
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Create a new, empty layer at the top of the
layer stack.
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3.
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Make sure only the needed layers are visible
(in this case the type layer and the paw print).
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4.
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Hold down the Option (Alt) key and choose
Layer > Merge Visible. This will create a flattened copy on the
recently created blank layer.
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5.
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Choose Help > Export Transparent Image. A
window opens displaying the interactive wizard.
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6.
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You now must tell Photoshop how to determine
transparency. The easiest method is to have the image on a
transparent background, but you can also make a selection using any
of your selection tools as well. The sample image is already on a
transparent background.
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7.
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The
next
window asks you to choose from Print
or Online. For this purpose, choose Print.
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8.
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Another window opens displaying advanced
options. Choosing to embed Vector Data (if you have any) is usually
all you need to select.
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9.
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Name
the file and set a destination. Photoshop
automatically creates the path and saves the image in the right
file format for PostScript printers (an EPS file). If you are using
a non-PostScript printer, save the file as a TIFF.
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This path is functioning as a clipping path.
When the path's name appears outlined, it is being used as a
clipping path.
Feel free to visit the Adobe Help Center (Help
> Photoshop Help) for more information on clipping paths. You'll
find advanced options on controlling the creation of work paths
(which become clipping paths).
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