Teach Yourself Photoshop 4 in 14 Days -- Ch 4 -- Color Modes and Models






Teach Yourself Photoshop 4 in 14 Days







- 4 -
Color Modes and Models

Color is all around us, a blessing few of us take time to think about
or recognize. It is as common (for those of us without visual impairments) as the
air we breathe, but when you become aware of its presence, you become aware of the
minute variations that exist in every color. Notice the shades of green on the tree
outside your window. Notice how those greens differ from the green of the grass.
Watch the play of light and shadow. It becomes fascinating. This chapter will try
to give you the beginnings of handling color in Photoshop.
Pixels and Bit Depth
So, we all know what color is, but how is color represented on a computer screen,
much less color on paper (which we will get to later today)?
The computer, as you may already know, is based on a binary data system--simply
put, ones and zeroes. In a computer, a "switch" is either on or off. This
is a rather basic and simplified look at that complex machine on your desk, but when
thinking of pixels, it becomes useful.
A pixel (a short for picture element) is a small block on the grid of your
screen and there are 72 pixels in an inch. These pixels can be either on or off,
which is to say, black or white. Of course, more colors than that are available on
most computers.
The capability to display multiple colors (up to 16.7 million) on a modern monitor
is a result of a pixel's bit depth. Bit depth refers to how many colors a
single pixel can represent. A pixel with a bit depth of 8 can display 2 to
the 8th power of colors--256 colors. A bit depth of 16 displays 65,636 colors. A
bit depth of 24 can display 16.7 million colors, or 2 to the power of 24.
This has quite an impact on the resolution and clarity of your images, but, as
with every positive comes the inherent negative: the brighter, crisper, and more
life-like your image is, the more memory it will consume. It is not uncommon to be
working with files that consume 10 or more megabytes of memory, and for images with
larger dimensions, you are looking at an even greater size.





NOTE: Does any of this sound familiar? If not, you might take a
trip into your Control Panels (on Macintosh or Windows) and open the one that controls
your monitor, called either Monitors or Display. Open the control panel and note
the color options you can select--depending on your monitor, this can be anything
from black and white all the way up to high color at 16 million.
I suggest that when you are working with Photoshop your monitor should be at the
highest resolution possible. It will slow your machine somewhat, but it is important
to be able to see your work.





Beginning Color
Now that we have discussed a little about color and how the machine displays color,
imagine trying to set up a system that accounts for these colors. Where would you
start? How do you separate the subjective view of color from the objective perception
of color? Not an easy task.
Color is defined in terms of color spaces and gamuts (see Figure
4.1). These attempt to address the full range of color. The human eye is capable
of perceiving a greater number of colors than machines can display or print. Thus,
the color spaces are subsets of the human perception.
Figure 4.1
Color Gamuts.
A color space is the entire range of possible colors. A gamut refers to all of
the colors within a given color model. Thus, a gamut is a subset of a space.
Today we are going to investigate the different properties of color--both in Photoshop
and in real life. Some of the information at the beginning might seem a little esoteric,
but in the long run, it's valuable to know. After all, the more you know about color
and how Photoshop addresses it, the better off you'll be. But don't worry, I'll try
to be as brief and painless as possible.
The first thing to know is that Photoshop addresses color in terms of models.
The color models are as follows:


RGB (Red, Green, Blue)


CMYK (Cyan, Magenta, Yellow, Black)


CIE Lab


HSB (Hue, Saturation, and Brightness)


The most encompassing of these color models is CIE Lab. It defines a color gamut
that is broader than any of the other models. Lab color is designed to be device
independent, meaning that colors defined in this model will appear and print the
same no matter the machine. However, this is probably not a model you will use frequently.





NOTE: Photoshop uses the CIE model, because its gamut is so broad,
to convert from model to model. You, especially as a beginner, will probably not
have much use for this model. I suggest that you work in HSB, RGB, or CMYK. Let it
do its work in the background, enabling Photoshop to switch painlessly between color
models, keeping your color as consistent as possible.





Let's focus our attention now on what works and what you need to know to get up
and running. The other three models, HSB, RGB, and CMYK, will have much greater impact
on your work in Photoshop. We will examine these models for displaying and achieving
color, and then we will turn our attention to the Photoshop modes. The
modes are methods of reproducing color based on the models. In fact, Photoshop has
modes that precisely match the models.
Exercise: Getting Started with Color
Just for fun, why don't we dive in with some hands-on before we proceed? Working
through this exercise will give you a better idea of the concepts and ideas that
we will be exploring shortly. We'll look at a colorful image and examine how the
modes affect the way the color appears.
Now, let's take a crack at changing modes:


1. First, open the file 04file01 from the CD. This file is in .JPG format and
is currently defined by the RGB color mode. In the following steps, we will transform
this colorful image from grayscale, to Indexed Color, to CMYK. Let's change our image
to grayscale first.


Figure 4.2
The original figure.


2. Select Image+Mode+Grayscale. A dialog box will appear, asking you if you want
to discard the image's color information. Click OK. Photoshop then proceeds to examine
your image and assign all the colors to 256 shades of gray that range between white
and black, inclusive.

Notice in the status bar how the size of your file diminishes. This is because color
is difficult for a machine to reproduce. The amount of information or data in a color
image is much greater than that required to display a grayscale image.


Figure 4.3
Changed to grayscale. All of the color values were assigned a value of gray between
1 and 256--1 being white and 256 being black.


3. Before we move on, we need to return the image to its original RGB state.
Select File+Revert. When Photoshop asks if you want to return to the last saved version
of 04file01, click OK.

This time, let's change our RGB image to CMYK (Cyan, Magenta, Yellow, and Black).
This process becomes enormously important for anyone who will be taking his or her
images to print. There are a number of colors that RGB can display because it is
an additive color system that CMYK, by the nature of its four inks, cannot reproduce.
The inks, for instance, can only approximate neon colors, but that is all. The human
eye is extremely sensitive to even the slightest variation in color. Think for a
moment about a can of Coca-Cola. I'll bet that if you were shown two swatches of
red, you could, without much hesitation, select the Coke red and differentiate it
from, say, the red used on the cover of Time magazine. Most people are very
susceptible to slight color changes. That is why color becomes so important in the
branding of products through advertising. To return to our Coke example, if you picked
up a can of Coke and it didn't have the signature red, maybe it was just a little
off, you might think that there was something wrong with it, that it was old or perhaps
even an impostor.

Before we make the mode change, let's take a closer look at some of the colors in
our RGB image to see if they can be reproduced in CMYK.

4. Click the Eyedropper tool in the toolbox.


Figure 4.4
The Eyedropper.


5. Next, open the Colors palette by selecting Window+Show Color.

6. Use the Eyedropper to select (click on) a color in the image. Try clicking in
the yellow to the image's right.

7. Look in the Color palette. Is there an out of gamut warning there? This little
triangle indicates that the selected color cannot be reproduced precisely by the
process colors of CMYK (see Figure 4.5).


Figure 4.5
An out of gamut warning.


To get an idea how far out of gamut your colors are, select View+Gamut Warning.
This gives you an indication of the colors that will be lost or modified during the
translation of one mode to CMYK.







NOTE: To change the color used in the display of the Gamut Warning,
select File+ Preferences+Transparency & Gamut. Click the color swatch at the
bottom of the dialog box and choose a color. I use red because it is the easiest
to see.
Now, select View+CMYK Preview. All of the colors that are out of gamut become
shaded with your selected color.







8. To change the mode from RGB to CMYK, select Image+Mode+CMYK.


If you have a color printer, you might want to print this document. Does it look
OK? Do the colors match what you see onscreen? If so, you're in luck. Your monitor
is accurately calibrated. If not, you will need to calibrate (adjust) your monitor
so that the images onscreen accurately display the colors as they will print.
We will discuss calibration later on today. For the moment, let's turn our attention
to the modes and models to get an idea of what was going on when we followed the
previous steps.
The Modes and Models of Color
The difference between the modes and the models is simple. The models are over-arching
methods of defining color, whereas modes are particular to Photoshop--the way Photoshop
defines the color. In this section, we will discuss both.
The Photoshop modes available under Image+Modes are as follows:


Bitmap
Grayscale
Duotone
Indexed Color
RGB Color
CMYK Color
Lab Color
Multichannel


Otherwise, the other models, CMYK and RGB, have corresponding modes in Photoshop.
In this section, we will also discuss the Grayscale mode and Indexed Color.
Before we begin, it must be said that the best way of learning this stuff is to
have Photoshop up and running on your machine. You will glean a certain amount of
information from merely reading, but the real learning won't start until you start
working in Photoshop. This is so for two reasons:


1. As we all know, you remember things better when you are doing it yourself.

2. Photoshop's treatment of color makes it very intuitive, just as selecting a color
was on Day 3, "Painting and Drawing Tools." Keep the Color palette open
at all times (Window+Show Color) and keep an eye on the sliders. Notice how they
change from mode to mode, as well as the differences and similarities.


Bitmap and Grayscale
We'll start out here with the most basic of the color modes available within Photoshop--Bitmap
and Grayscale.
The Bitmap mode uses only two color values to display images--black and white,
while the Grayscale mode offers 256 shades of gray that range from white to black
(see Figures 4.6 and 4.7 for examples).
Figure 4.6
An image ain the Grayscale mode.
Figure 4.7
The same image in the Bitmap mode.
Notice the vast difference in quality. The Grayscale image is clear and crisp,
whereas the bitmap image is not. There are, however, a number of ways to convert
to Bitmap mode, which we'll discuss later today (and this is not to be confused with
the Bitmap file format, which you can read about in Appendix C).
Duotones and Up
Duotones are a hybrid mode (black and white with 1 added color). If you have ever
seen old black and white photos in which the people's cheeks are rosy or their eyes
or hair are colored, you have seen a duotone. A duotone is a grayscale image to which
a color has been added. But why stop at just one extra color? Add up to four if you
like.
The HSB Model
The HSB model is based on how the human eye perceives color. HSB stands for Hue,
Saturation, and Brightness. Hue is the actual color--red, green, blue, and so on.
Saturation is the purity of the color, or how much gray is in proportion to the true
hue. Brightness is defined by the lightness or darkness of the color.
These components are very clear if you will select Window+Show Color. In the Colors
palette, click the menu in the upper right corner and select HSB.
The bar across the top of the palette is the Hue bar (see Figure 4.8). Select
colors from the bar at the bottom of the dialog. Notice the percentage in the box
to the right. The percentages correspond to the color's placement on the color wheel:


0= orange
90= green
180= cyan
270= purple


In the middle slider, you see the saturation component. To the far right, you
see the fully saturated color--the purest color. On the left of the saturation bar,
you will see gray or perhaps even white. Drag the slider back and forth, and watch
the foreground color swatch. Notice the change in the color.
In the brightness bar, you can drag to lighten or darken a color. Lighten it to
100% for the purest color; darken it to 0% and you will end up with black.
In the lower-left corner of the dialog box, you will occasionally see an Out of
Gamut warning, meaning that the process colors for printing cannot duplicate the
current color. Click the warning triangle to select the nearest color that can be
achieved with process colors. More information on CMYK and process colors will be
covered later in this chapter.
All of these attributes (Hue, Saturation, Brightness) combine to define color,
which is a natural and intuitive way of selecting color. The Color Picker in Figure
4.8 is set up in the HSB model. Note the radio buttons to the right of the color
window. Click the "S" radio button for saturation (see Figure 4.9). Notice
how this changes your color window. Figure 4.10 shows the "B" button checked.
Figure 4.8
The Color Picker set up in the HSB model.
Figure 4.9
The Color Picker with the Saturation radio button clicked.
Figure 4.10
The Color Picker with the Brightness radio button clicked.
When I am working in Photoshop, I tend to use the HSB color model most often because
it is so easy to adjust a color based on the way your eye perceives it. I know that
when I drag the brightness slider to the left I am going to get a darker color, and
I know when I increase the saturation that I am going to get a more vibrant color.
If you are planning on publishing your work on the web or in a multimedia presentation,
HSB is a perfectly fine color model in which to work--perhaps switching to Indexed
Color before finishing if you are web publishing (see Day 14). What you see is close
to what others will see on their monitors, but this is never an exact science-- especially
on the web. We will discuss more issues related to web publishing on Day 14.
The RGB Model
The RGB color model is based on the primary colors of red, green, and blue. This
is how your monitor displays color (by emitting light through phosphors). It is an
additive color model, meaning that if you add all of the colors at 100% of their
intensity, you get white. This also means, of course, that if you remove all of the
colors (or move their sliders each to 0), you will get black. Let's give this a try.
Select Window+Show Colors. In the Color palette's menu (the arrow in the upper-right
corner), select RGB Sliders (see Figure 4.11). This will ensure that we are working
in RGB from the start--saving us the trouble of converting modes.
Figure 4.11
The Color palette in RGB.
In the Color palette, you will notice that if you move one of the sliders, the
other two reflect the change. While in the HSB model where your adjustment of the
Hue component has a direct and intuitive effect on the Brightness component, adjusting
the RGB model isn't nearly as intuitive--but we don't have to be color experts as
long as we have the color bar at the bottom of the palette. Without delving too deeply
into the arcane secrets of color manipulation, we can usually come up with a pretty
good match or original color.
The CMYK Model
CMYK (Cyan, Magenta, Yellow, and Black) are known as the process colors.
These colors are the colors that generate most of the printed material you see, from
billboards to product packaging to magazines. To achieve the wide variety of colors
you see in, say, a fashion magazine, the four basic colors Cyan, Magenta, Yellow,
and Black are combined.
On the page, they appear as halftone dots, the size and angle of which
can be adjusted. The smaller the dots are, the less concentration of that particular
color. The angle controls how the dots mix with the surrounding inks.
At one time, in the not-so-distant past, people called imagesetters actually
did this by hand--setting up screens with angles for the halftones--but the advent
of desktop computers and desktop publishing has all but rendered them extinct.
To get a clearer idea of what is really going on with four-color or process printing,
read the following section. In it we examine, close up, what a four-color image looks
like.
Examining CMYK Color
CMYK colors are used in professional printing and are a super set of the inks
used in most consumer model color printers. Most home-based color printers use only
CMY.
Take, for example, any color magazine. Find a picture (flesh tones are great for
this), and look at it through a magnifying glass. Printers and prepress professionals
use a fancy magnifying glass called a loupe (pronounced "loop").
If you look closely enough, you will see moirés. These are patterns
of dots made up of the four process colors. With these dots, set at different percentages
and varying angles, you can create almost any color you might need. Try this:


1. Open image file 04file01 from the CD.

2. Select Mode+CMYK to change the mode to CMYK.

3. Open the Channels palette (Windows+Channels palette) shown in Figure 4.12.


Figure 4.12
The Channels palette.


4. Next, click the eye icons in the Channels palette. This turns a channel on
and off. Notice how the image changes. Try turning off magenta and yellow. The remaining
color, cyan, comes to dominate the image.


Here is another variation that will show you a better picture of how CMYK dots
are arranged in an image to create the illusion of color.


1. With the Marquee tool, select the bottom part of the image.

2. Select Filter+Pixelate+Color Halftone (see Figure 4.13).


Figure 4.13
The Color Halftone dialog box.


3. In the Color Halftone dialog box, set the maximum radius to four pixels. Click
OK when you're done (see Figure 4.14).


Figure 4.14
The halftone result.

The result is a "magnified for effect" version of what really happens in
the creation of 4-color images. Notice the different size of dots. Also note the
angles at which they are set in relation to each other. This is how the broad spectrum
of printed color that you see in most publications is usually created.
Working with CMYK
As I said earlier, the best way to learn to work with color in Photoshop is to
have Photoshop up and running on your machine, the Color palette open, this book
propped beside you, and perhaps your favorite beverage nearby.
So, to start off, select Window+Show Color. In the Color palette's menu (the arrow
in the upper-right corner), select CMYK Sliders. This ensures that we are working
in CMYK from the beginning, keeping us in the gamut.
CMYK is not an intuitive color mode. As with RGB, each adjustment you make to
a particular color has echoed effects on the other colors. Say, for instance, you
drag the Cyan slider to the far right, increasing the presence of the color Cyan
to 100%. The other colors will assume a bluish cast. If you drag it to the left,
effectively removing Cyan altogether, the other colors will assume a pinkish hue--given
that the Black component isn't turned up too high.





NOTE: If you want to preview the colors available to you, without
trying all of them in Photoshop, PANTONE offers swatch books. These are "ready-mixed"
colors that you can have your professional printer use, but they also enable you
to preview colors, because they include the CMYK and RGB color percentages, which
you can simply enter into the Color Picker's dialog boxes. This ensures a true color,
regardless of the monitor's calibration. What you see on the swatch is what you will
get.





Indexed Color
Indexed Color, when it can work for you, is a wonderful thing. It is a palette,
or I should say, a collection of palettes--7 in all, in most of which you get 256
colors. With this mode you know exactly what you are getting, and if you don't like
any of the palettes Photoshop supplies, you can build your own.
First of all, Indexed Color is a blessing for the World Wide Web. Web browsers
can only accurately display 216 colors and these are reserved in a palette for Indexed
Color images.
But before you think that this mode is only capable of 256 colors, let me set
you straight, because this is not the case. Dithering takes place in Indexed Color
images. This means that certain colors are combined, that is, adjacent pixels
are blended onscreen to create a third (or 257+) color. Let's take a look at the
Indexed Color dialog box. Select Image+Modes+Indexed Color (see Figure 4.15).
Figure 4.15
The Indexed Color dialog box.
You are given a number of palette choices when you work with Indexed Color. They
are as follows:


Exact: This option takes the colors that are in the RGB version of the
image for its palette. This only works if there are less than 256 colors in the original
image.


System (Macintosh): This option uses the Macintosh system palette.


System (Windows): This option uses the Windows system palette.


Web: This palette uses the colors most often used by web browsers (the
safe 216). If you are planning to publish your work on the World Wide Web, this is
the palette in which you should do most of your work. Otherwise, you might have problems
with incompatible colors dropping out when viewed with a web browser.


Uniform: The Uniform option bases the colors in the palette on a strict
sampling of colors across the color spectrum.


Adaptive: This is your best bet for most work in Indexed Color. During
conversion, this option samples the most frequently used colors from the original.
Adaptive will usually provide you with the closest match to the original image.







NOTE: Here's a clever trick when converting an image into Indexed
Color using the Adaptive palette. Make a selection in the image before converting.
This way, the colors in the marquee will take precedence as Photoshop converts the
entire image.







Custom: If none of the other options suit you, you can always build your
own palette.


To work with a custom palette:




1. Open the file lettuce.tif from the CD.
2. Select Image+Mode+Indexed Color.
3. In the Indexed Color dialog box, choose Custom from the drop-down menu. Click
OK.
4. When you do so, you will be presented with the Custom Color Table dialog box
(see Figure 4.16). Here you also have a number of choices in the drop-down menu at
the top of the box. A few, such as Windows and Macintosh, we looked at in the preceding
numbered list. Spectrum offers precisely that--the colors of the visible spectrum
of light. Grayscale gives you the 256 shades of gray. Blackbody (one of my favorites)
is made up of the colors of a heated body.


Figure 4.16
The Color Table dialog box.





NOTE: Try this. Open a new file with a white background. Paint on
it with black. Paint whatever comes to mind. Now convert the image to Indexed Color
and select Custom. In the Custom Color Table, select Blackbody. Click OK. What do
you think?





But this still isn't what we're looking for. We need to create our own palette.
Here's how you do it:


1. Click one of the 256 squares in the table.

2. The Color Picker (or one of its variants will appear).

3. Select a color.

4. Click OK. This automatically inserts your newly chosen color into the palette.







NOTE: If an image is already in Indexed Color, choose Image+Mode+Color
Table to define a Custom color table.





That color is now part of your table, but this would take forever to accomplish
by hand, opening every single box and defining every single color, so Photoshop makes
it easy:


1. Click in the first swatch of color in the color table and drag to select all
of the colors in the table.

2. The Color Picker opens (see Figure 4.17). Select a starting color.


Figure 4.17
The Color Picker. Select your starting color.


3. Click OK.

4. The Color Picker opens again automatically. Select a finishing color.

5. Click OK.


Photoshop will do the calculations for you, choosing colors two through 255, based
on your selections. How's that for easy?
When you have found a color table that you like, save it using the Save command
in the Custom Color Table. You also can open previously saved colors by using the
Load command.
Converting Between Modes
The real trick to successfully working in color is knowing what mode you need,
what mode lends itself to your particular output plans. If you plan to print your
work, you need CMYK. If you plan to publish your work on the web or use it in multimedia,
I suggest that you work in either RGB and save your images with Indexed Color.
All you have to do to convert, at least mechanically (this is not taking into
account image degradation or changes), is select Image+Mode+ and then choose your
poison.
Although Photoshop uses the model (Lab) with the broadest gamut of color to change
color modes (as if all of the other modes are circles that will fit with Lab color),
this is no guarantee that your colors are going to turn out.
The rule of thumb is this and I can't stress it enough: don't work in RGB if you
are going to output your images to print. Instead, work in CMYK. If you are going
to publish your images on the web, use Indexed Color (or use RGB and then convert).
Knowing this will save you many hours of wondering why that web page looks funky
on the Windows machine you use at home, or why the yellow in your printed piece looks
brownish.
But what if the color mode you want happens not to be available in the Image+Mode
menu? Nothing to worry about. It is true that sometimes the mode you want will not
be available, but you can always get to it by first converting to Lab Color and then
to the color you want. For example, when you have created or imported an image that
is in Indexed Color, the CMYK option is grayed out, or not available. You actually
have two choices here. Convert to Lab or RGB and then take the image over into CMYK,
but beware. Make sure that the color is the one you want.
Converting to Bitmap from Grayscale and Vice Versa
Most color conversions are simply a matter of choosing the desired mode from the
Image+Mode menu and crossing your fingers. There are, however, a number of options
when converting between Grayscale and Bitmap (you can only convert to Bitmap mode
from the Grayscale mode). Figure 4.18 displays the image we'll be using in this section.
Figure 4.18
Original Image.
In Figure 4.19, you will see the Bitmap dialog box (Image+Modes+Bitmap).
Figure 4.19
Bitmap mode options.
Let's explore the options you have with the Bitmap mode:


1. Open file lion.tif from the CD.

2. The first thing you should do is set the output ratio. Don't go much higher than
what you see listed as the current ratio. If you do, you will get a much larger,
much grainier image than you want. See Figure 4.20 for an image sampled up from 72
pixels per inch (as seen in Figure 4.19) to 300 pixels per square inch.


Figure 4.20
300 pixels per square inch.


3. The next thing you have to do is choose the method. You have four choices:




50% Threshold: Converts pixels in the grayscale that are above the midway
point in the 256 color palette to white. Those that fall below fall into black. This
creates a high contrast image (see Figure 4.21).


Figure 4.21
50% Threshold.


Pattern Dither: This option converts the grayscale into geometric patterns
of dots (see Figure 4.22).


Figure 4.22
Pattern Dither.


Diffusion Dither: This option offers a smoother alternative to pattern
dither, using a process that evaluates each pixel for its value (see Figure 4.23).


Figure 4.23
Diffusion Dither.


Halftone Screen: This option is your best bet for printing because you
can specify exactly how the halftone dots (which we discussed in the section on CMYK)
are set up.




4. Now, let's pick up where we left off. In the Bitmap dialog box, click Halftone
Screen. You will see the dialog box in Figure 4.24.


Figure 4.24
The Halftone Screen dialog box.


5. The Frequency option relates to the type of paper stock you will be using.
For very porous paper, such as newsprint, select a low frequency, something like
80 or 90. Otherwise, the dots will run together as the paper absorbs the ink. For
higher quality paper stock, set the frequency higher.

6. The screen angle refers to the angle of the dots. For black and white images,
stick with a 45° angle.

7. In the bottom of the dialog box, choose a shape for the dots. In this example,
I chose elliptical dot (see Figure 4.25).


Figure 4.25
Halftone Screen.
Here is another alternative for converting to the Bitmap mode. This involves filling
the image with a pre-defined pattern.


1. Open the images Twisted.tif and lion.tif from the CD (see Figure 4.26).


Figure 4.26
The twisted.tif.


2. Click in the Twisted.tif image.

3. Choose Select+All.

4. Select Edit+Copy.

5. To define the pattern, select Edit+Define Pattern.

6. Next, click in the lion image, and choose Image+Mode+Bitmap.

7. In the dialog box, select Custom Pattern (see Figure 4.27).


Figure 4.27
The Custom Pattern option.


8. Click OK (see Figure 4.28).


Figure 4.28
The finished product.

This option takes the pattern you defined and creates the bitmap image with it. It
is an interesting effect and could be used in conjunction with a filter (see Day
12 for more information on filters).
Color Channels
Color channels are great. Remember way back at the beginning of today, when you
tried to adjust a component of CMYK, but couldn't adjust it alone without affecting
its counterparts? Well, with channels, sometimes referred to as alpha channels,
you can.
Channels make up the different color components of images. Bitmap, Grayscale,
Duotone, and Indexed Color have only one channel, whereas RGB has three and CMYK
has four.
Try turning off a color channel by clicking the eye icon in the far left of the
palette. This removes that particular color. Thus, whatever changes you make to the
image at this point (which you will learn about tomorrow) leaves this channel unaffected.
To create a new channel, simply click the New Channel button at the bottom of
the dialog box. To delete a channel, select it in the options palette and drag it
onto the Trash icon at the bottom of the palette.
Monitor Calibration
The first thing to note here is that if you are satisfied with your four-color
printed pieces (or three-color depending on your printer), then read no further.
This section is only for those people who are experiencing difficulties and discrepancies
between what they see on their monitors and what is printed out, or who want to improve
their print-outs, which is probably everybody at one time or another.
To begin with, you need to make a print-out of the file testpic.jpg (or Ole no
Moire on Macs). You will find this in your Photoshop folder in the Goodies folder+Calibration
folder. How does it look? Great? Not so great? Let's see what we can do about that.
First, make sure that your monitor has been on for a while, at least a half an
hour, and second, make sure that you have turned off any desktop patterns or background
images you might have set up on your computer's desktop. Although these features
might be visually interesting, they might detract from your ability to see color
as it truly appears. Colors, when placed in close proximity to one another, significantly
affect how we perceive them. Blue, for example, will appear much differently on a
background of white than on a background of, say, bright yellow.





NOTE: For those of you who are Windows users, this is less of a
concern because Photoshop provides an entire desktop workspace for you. On the Macintosh,
however, the desktop is still quite visible in the Standard Screen Mode.





Next, make sure that the lighting in your work environment is as it is when you
are working. Try to set up your area as you generally have it--adjust the brightness
and contrast so that viewing is comfortable. With the setup as you want it, you should
in some way mark the controls so that if they are changed, you can easily change
them back (as they say, "Don't touch that dial"). This way, you can compensate
for the glare from external office lights or windows.





NOTE: The only real difference between calibrating a Macintosh and
a Windows machine is in the location of the Gamma control panel. On a Macintosh,
you will find this in the Control Panels folder. On a Windows machine, you can only
reach it after going through the Color Preferences command. I will note this as we
go through the process.





Now, we can proceed to the actual calibration steps:


1. First, you should open a blank canvas using File+New and selecting white as
the background color. You also can open file Testpic.jpg (Windows) or Ole No Moire
(Macintosh) from the Calibration folder within the Photoshop application folder (see
Figure 4.29).


Figure 4.29
Testpic.jpg.


2. On the Macintosh, open the Gamma control panel from the Control Panels folder
(if it was not automatically installed with Photoshop, you will find it in the Calibration
folder as shown in Figure 4.30). Click the On button. On a Windows machine, select
File+Color Settings+Monitor Setup (see Figure 4.31).


Figure 4.30
The Gamma Control Panel.
Figure 4.31
The Monitor Setup dialog box.


3. Now select a gamma. On the Macintosh, select a target gamma at the top of
the control panel. On a Windows machine, type in a target. 1.8 is recommended for
printing output (CMYK). If, however, you are going to use your work in a multimedia
environment, you might want to select a higher target, such as 2.2
4. For Windows users: click Calibrate in the Monitor Setup dialog box. A new dialog
box very similar to the Mac's gamma control panel will appear (see Figure 4.32).


Figure 4.32
The Windows version of the Gamma Control Panel.


5. To set the white point, click the White Point radio button. Take a piece of
the paper you will be using for printing (or a kind very similar) and hold it next
to the monitor. This may not sound high-tech, but printing is that magical bridge
between the real and the virtual world, so bear with us. With your blank piece of
paper as a guide, drag the sliders in the dialog box until what you see onscreen
matches the blank hard copy in your hand.
6. To adjust the gamma, drag the slider to match the gray swatches.







NOTE: Windows users: Do not overlook the Preview button in the lower
left-hand corner of the dialog box. With it, you can immediately see the consequences
of your adjustments.







7. To adjust the color, click the Color Balance radio button and adjust by dragging
the sliders. This compensates for color casts in the monitor.

8. Finally, to adjust the Black point, click the Black Pt radio button and drag the
sliders to the left (usually almost all the way) but not so far that you can't see
the gradations of black to gray to white.


When you have reached a level of calibration that is acceptable to you, you should
save the settings. Simply select Save Settings in the Gamma control panel (or dialog
box, for Windows users), name your settings, and click OK. This also enables you
to create different settings for different users, types of paper, and for different
output options (electronic versus printed).
Summary
If you weren't aware of the complexities of not only representing color electronically
or physically with ink, but of the sheer complexity of color itself, I hope that
this chapter opened your eyes to some of the aspects in this delicate art. A person
could spend years learning about color, and I hope that you will pursue a deeper
knowledge than was presented here, but I also hope that you got enough of an idea
of how to use color so that you can get your machine up and running the way you want.
In this chapter, we discussed the color modes and the specific color models in
Photoshop. We also looked at a few of the more salient issues regarding converting
between modes. The one thing to remember is that although Photoshop uses the Lab
model, the color model with the most encompassing gamut, to govern conversions, there
is always the possibility of color loss. Try, if it is at all possible, to work in
the mode in which you will output your final product.
And finally today, we took a brief tour of the calibration tools for Photoshop.
It is not always easy to match the color of electronic images with their printed
forms (or even electronic forms on other platforms and machines), but a solid approach
to calibration can go a long way toward reducing this chasm.
Tomorrow, you will delve deeper into the world of color by learning how to make
tonal adjustments and general adjustments.








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