Photoshop 6 for Windows Bible- P28 pptx

Figure 17-15: Use the Levels dialog box to map brightness values in the image Input Levels to new brightness values Output Levels.. For example, if you raise the value to 55, all colors

Consider the digital photograph featured in Color Plate 17-12 Snapped several years

back in Boston’s Copley Square using a Kodak DC50 digital camera, the original image

at the top of the color plate is drab and lifeless If I used the Hue/Saturation command

to pump up the saturation levels, a world of ugly detail rises out of the muck, as

shown in the second example (Obviously, I’ve taken the saturation a little too high,

but only to demonstrate a point.) The detail would have faired no better if I had used

the Variations command to boost the saturation

Unstable colors may be the result of JPEG compression, as in the case of the digital

photo Or you may have bad scanning or poor lighting to thank In any case, you can

correct the problem using our friends the Median and Gaussian Blur commands, as

I explain in the following steps

If you find yourself working with heavily compressed images on a regular basis, you

may want to record these steps with the Actions palette, as explained in Chapter B

on the CD-ROM at the back of this book Unlike the “Adjusting the Focus of Digital

Photos” steps back in Chapter 10, you won’t want to apply these steps to every

dig-ital photograph you take — or even most of them — but they come in handy more

often than you might think

STEPS: Boosting the Saturation of Digital Photos

1 Select the entire image and copy it to a new layer It seems like half of all

Photoshop techniques begin with Ctrl+A and Ctrl+J

2 Press Ctrl+U to display the Hue/Saturation dialog box Then raise the

Saturation value to whatever setting you desire Don’t worry if your image

starts to fall apart — that’s the whole point of these steps Pay attention to

the color and don’t worry about the rest In the second example in Color

Plate 17-12, I raised the Saturation to +80

3 Choose Filter ➪ Noise ➪ Median As you may recall from the last module,

Median is the preeminent JPEG image fixer A Radius value of 4 or 5 pixels

works well for most images You can take it even higher when working with

resolutions of 200 ppi or more I used 5 This destroys the detail, but that’s

not important The color is all that matters

4 Choose Filter ➪ Blur ➪ Gaussian Blur As always, the Median filter introduces

its own edges And this is one case where you don’t want to add any edges, so

blur the heck out of the layer I used a Radius of 4.0, just 1 pixel less than my

Median Radius value

5 Select Color from the blend mode pop-up menu in the Layers palette.

Photoshop mixes the gummy, blurry color with the crisp detail underneath

I also lowered the Opacity to 70 percent to produce the third example in

Color Plate 17-12

My image was still a little soft, so I applied the digital-photo sharpening steps fromChapter 10 After flattening the image, I pressed Ctrl+A and Ctrl+J again to copy it

to yet another new layer Then I applied the Median, Gaussian Blur, and UnsharpMask filters, flattened the image one last time, and sharpened the image to taste.The finished result appears at the bottom of Color Plate 17-12 Although a tad toocolorful — Boston’s a lovely city, but it’s not quite this resplendent — the edges lookevery bit as good as they did in the original photograph, and in many ways better

Making Custom Brightness Adjustments

The Lighter and Darker options in the Variations dialog box are preferable to theLightness slider bar in the Hue/Saturation dialog box because you can specifywhether to edit the darkest, lightest, or medium colors in an image But neithercommand is adequate for making precise adjustments to the brightness and con-trast of an image Photoshop provides two expert-level commands for adjusting the brightness levels in both grayscale and color images:

✦ The Levels command is great for most color corrections It lets you adjust

the darkest values, lightest values, and midrange colors with a minimum offuss and a generous amount of control

✦ The Curves command is great for creating special effects and correcting images beyond the help of the Levels command Using the Curves command,

you can map every brightness value in every color channel to an entirely ferent brightness value

dif-In the back rooms of some print houses and art shops, a controversy is brewingover which command is better, Levels or Curves Based on a few letters I’vereceived over the years, it seems that some folks consider Curves to be the command for real men and Levels suitable only for color-correcting wimps

Naturally, this is a big wad of hooey Levels provides a histogram, which is lutely essential for gauging the proper setting for black and white points Meanwhile,Curves lets you map out a virtually infinite number of significant points on a graph.The point is, both commands have their advantages, and both offer practical bene-fits for intermediate and advanced users alike

abso-There’s no substitute for a good histogram, so I prefer to use Levels for my day color correcting If you can’t quite get the effect you want with Levels, or youknow that you need to map specific brightness values in an image to other values,use Curves The Curves command is the more powerful function, but it is likewisemore cumbersome

day-to-Note

The Levels command

When you choose Image ➪ Adjust ➪ Levels (Ctrl+L), Photoshop displays the Levels

dialog box shown in Figure 17-15 The dialog box offers a histogram, as explained

in the “Threshold” section earlier in this chapter, as well as two sets of slider bars

with corresponding option boxes and a few automated eyedropper options in the

lower-right corner You can compress and expand the range of brightness values in

an image by manipulating the Input Levels options Then you can map those

bright-ness values to new brightbright-ness values by adjusting the Output Levels options

Figure 17-15: Use the Levels dialog box to map brightness

values in the image (Input Levels) to new brightness values

(Output Levels)

The options in the Levels dialog box work as follows:

✦ Channel: Select the color channel that you want to edit from this pop-up

menu You can apply different Input Levels and Output Levels values to each

color channel However, the options along the right side of the dialog box

affect all colors in the selected portion of an image regardless of which

Channel option is active

✦ Input Levels: Use these options to modify the contrast of the image by

dark-ening the darkest colors and lightdark-ening the lightest ones The Input Levels

option boxes correspond to the slider bar immediately below the histogram

You map pixels to black (or the darkest Output Levels value) by entering a

number from 0 to 255 in the first option box or by dragging the black slider

triangle For example, if you raise the value to 55, all colors with brightness

values of 55 or less in the original image become black, darkening the image

as shown in the first example of Figure 17-16

You can map pixels at the opposite end of the brightness scale to white (orthe lightest Output Levels value) by entering a number from 0 to 255 in thelast option box or by dragging the white slider triangle If you lower the value

to 200, all colors with brightness values of 200 or greater become white, ening the image as shown in the second example of Figure 17-16 In the lastexample of the figure, I raised the first value and lowered the last value,thereby increasing the amount of contrast in the image

light-One of my favorite ways to edit the Input Levels values is to press the up anddown arrow keys Each press of an arrow key raises or lowers the value by 1.Press Shift with an arrow key to change the value in increments of 10

Figure 17-16: The results of raising the first Input Levels value to 55 (left),

lowering the last value to 200 (middle), and combining the two (right)

✦ Gamma: The middle Input Levels option box and the corresponding gray

triangle in the slider bar (shown highlighted in Figure 17-17) represent thegamma value, which is the brightness level of the medium gray value in theimage The gamma value can range from 0.10 to 9.99, with 1.00 being dead-onmedium gray Any change to the gamma value has the effect of decreasing the amount of contrast in the image by lightening or darkening grays withoutchanging shadows and highlights Increase the gamma value or drag the gray

slider triangle to the left to lighten the medium grays (also called midtones),

as in the first and second examples of Figure 17-18 Lower the gamma value ordrag the gray triangle to the right to darken the medium grays, as in the lastexample in the figure

Tip

You can edit the gamma value also by pressing the up and down arrow keys.

Pressing an arrow key changes the value by 0.01; pressing Shift+arrow changes

the value by 0.10 I can’t stress enough how useful this technique is I rarely do

anything except press arrow keys inside the Levels dialog box anymore

Figure 17-17: To create the spotlighting effects you see here,

I selected the circular areas, inversed the selection, and applied

the values shown in this very dialog box

Figure 17-18: The results of raising (left and middle) and lowering

(right) the gamma value to lighten and darken the midtones in an image

✦ Output Levels: Use these options to curtail the range of brightness levels in

an image by lightening the darkest pixels and darkening the lightest pixels.You adjust the brightness of the darkest pixels — those that correspond to the black Input Levels slider triangle — by entering a number from 0 to 255

in the first option box or by dragging the black slider triangle For example,

if you raise the value to 55, no color can be darker than that brightness level(roughly 80 percent black), which lightens the image as shown in the firstexample of Figure 17-19 You adjust the brightness of the lightest pixels —those that correspond to the white Input Levels slider triangle — by entering

a number from 0 to 255 in the second option box or by dragging the whiteslider triangle If you lower the value to 200, no color can be lighter than thatbrightness level (roughly 20 percent black), darkening the image as shown inthe second example of Figure 17-19 In the last example of the figure, I raisedthe first value and lowered the second value, thereby dramatically decreasingthe amount of contrast in the image

You can fully or partially invert an image using the Output Levels slider gles Just drag the black triangle to the right and drag the white triangle to theleft past the black triangle The colors flip, whites mapping to dark colors andblacks mapping to light colors

trian-Figure 17-19: The result of raising the first Output Levels value to 55 (left),

lowering the second value to 200 (middle), and combining the two (right)

✦ Load/Save: You can load and save settings to disk using these buttons.

✦ Auto: Click the Auto button to automatically map the darkest pixel in your

selection to black and the lightest pixel to white, as if you had chosen Image ➪Adjust ➪ Auto Levels Photoshop actually darkens and lightens the image by

an extra half a percent just in case the darkest and lightest pixels are cally inconsistent with the rest of the image

statisti-To enter a percentage of your own, Alt-click the Auto button (the button namechanges to Options) This displays two additional options, Black Clip and WhiteClip Enter higher values to increase the number of pixels mapped to black andwhite; decrease the values to lessen the effect Figure 17-20 compares the effect

of the default 0.50 percent values to higher values of 2.50 and 9.99 percent Asyou can see, raising the Clip value produces higher contrast effects

Figure 17-20: The default effect of the Auto button (left) and the effect of the

Auto button after raising the Clip values (middle and right)

Any changes made in the Auto Range Options dialog box also affect the formance of the Auto Levels command At all times, the effects of the Autobutton and Auto Levels command are identical

per-✦ Eyedroppers: Select one of the eyedropper tools in the Levels dialog box

and click a pixel in the image window to automatically adjust the color of that pixel If you click a pixel with the black eyedropper tool (the first of thethree), Photoshop maps the color of the pixel and all darker colors to black

If you click a pixel with the white eyedropper tool (the last of the three),

Note

Photoshop maps it and all lighter colors to white Use the gray eyedroppertool (middle) to change the color you clicked to medium gray and adjust allother colors in accordance For example, if you click a light pixel, all light pix-els change to medium gray and all other pixels change to even darker colors.One way to use the eyedropper tools is to color-correct scans without a lot ofmessing around Include a neutral swatch of gray with the photograph youwant to scan (For those who own a Pantone swatch book, Cool Gray 5 or 6 isyour best bet.) After opening the scan in Photoshop, choose the Levels com-mand, select the gray eyedropper tool, and click the neutral gray swatch inthe image window This technique won’t perform miracles, but it will help you

to distribute lights and darks in the image more evenly You then can fine-tunethe image using the Input Levels and Output Levels options

By default, the eyedroppers map to white, gray, and black But you can changethat Double-click any one of the three eyedroppers to display the Color Pickerdialog box For example, suppose you double-click the white eyedropper, setthe color values to C:2, M:3, Y:5, K:0, and then click a pixel in the image win-dow Instead of making the pixel white, Photoshop changes the clicked color —and all colors lighter than it — to C:2, M:3, Y:5, K:0, which is great for avoidinghot highlights and ragged edges

To give you a sense of how the Levels command works, the following steps describehow to improve the appearance of an overly dark, low-contrast image such as thefirst example in Color Plate 17-13 Thanks to natural lighting and the dark color ofthe stone, this statue of Thomas Jefferson is hardly recognizable Luckily, you canbring out the highlights using Levels

STEPS: Correcting Brightness and Contrast with the Levels Command

1 Press Ctrl+L to display the Levels dialog box The histogram for the Jefferson

image appears superimposed in white in front of the great man’s chest As youcan see, most of the colors are clustered on the left side of the graph, showingthat there are far more dark colors than light

2 Press Ctrl+1 to examine the red channel Assuming that you’re editing an RGB

image, Ctrl+1 displays a histogram for the red channel The channel-specific tograms appear below Jefferson, colorized for your viewing pleasure

his-3 Edit the black Input Levels value as needed Drag the black slider triangle to

below the point at which the histogram begins In the case of Jefferson, youcan see a spike in the histogram about a half pica in from the left side of thegraph I dragged the black triangle directly underneath that spike, changingthe first Input Levels value to 14, as you can see in the red histogram on theright side of Color Plate 17-13

Tip

Tip

4 Edit the white Input Levels value Drag the white slider triangle to below the

point at which the histogram ends In the color plate, the histogram features

a tall spike on the far right side This means a whole lot of pixels are already

white I don’t want to create a flat hot spot, so I leave the white triangle alone

5 Edit the gamma value Drag the gray triangle to the gravitational center of the

histogram Imagine that the histogram is a big mass, and you’re trying to

bal-ance the mass evenly on top of the gray triangle Because my histogram is

weighted too heavily to the left, I had to drag the gray triangle far to the left

until the middle Input Levels value changed to 2.40, which represents a

radi-cal shift

6 Repeat Steps 2 through 5 for the green and blue channels Ctrl+2 takes you

to the green channel; Ctrl+3 takes you to blue Your image probably has a

sig-nificant preponderance of red about it To correct this, you need to edit the

green and blue channels in kind The graphs on the right side of Color Plate

17-13 show how I edited my histograms Feel free to switch back and forth

between channels as much as you like to get everything just right

7 Press Ctrl+tilde (~) to return to the composite RGB histogram After you get

the color balance right, you can switch back to the composite mode and

fur-ther edit the Input Levels I typically bump up the gamma a few notches — to

1.2 or so — to account for dot gain

You may notice that your RGB histogram has changed Although the histograms

in the individual color channels remain fixed, the composite histogram updates

to reflect the red, green, and blue modifications I’ve superimposed the updated

histogram in white on the corrected Jefferson on the right side of Color Plate

17-13 As you can see, the colors are now better distributed across the

bright-ness range

8 Press Enter to apply your changes Just for fun, press Ctrl+Z a few times to

see the before and after shots Quite the transformation, eh?

If you decide after looking at the before and after views that you could do a

better job, undo the color correction and press Ctrl+Alt+L to bring up the

Levels dialog box with the previous settings intact Now you can take up

where you left off

The Curves command

If you want to be able to map any brightness value in an image to absolutely any

other brightness value — no holds barred, as they say — you want the Curves

com-mand When you choose Image ➪ Adjust ➪ Curves (Ctrl+M), Photoshop displays the

Curves dialog box, shown in Figure 17-21, which offers access to the most complex

and powerful color correction options on the planet

Tip

Figure 17-21: The Curves dialog box lets you distribute

brightness values by drawing curves on a graph

Quickly, here’s how the options work:

✦ Channel: Surely you know how this option works by now You select the color

channel that you want to edit from this pop-up menu You can apply differentmapping functions to different channels by drawing in the graph below thepop-up menu But, as is always the case, the options along the right side ofthe dialog box affect all colors in the selected portion of an image regardless

of which Channel option is active

✦ Brightness graph: The brightness graph is where you map brightness values in

the original image to new brightness values The horizontal axis of the graph

represents input levels; the vertical axis represents output levels The ness curve charts the relationship between input and output levels The lower-

bright-left corner is the origin of the graph (the point at which both input and outputvalues are 0) Move right in the graph for higher input values and up for higheroutput values Because the brightness graph is the core of this dialog box,upcoming sections explain it in more detail

By default, a trio of horizontal and vertical dotted lines crisscross the ness graph, subdividing it into quarters For added precision, you can dividethe graph into horizontal and vertical tenths Just Alt-click inside the graph totoggle between tenths and quarters

bright-Tip

Brightness curveBrightness graph

Brightness barCurve toolsEyedroppers

✦ Brightness bar: The horizontal brightness bar shows the direction of light and

dark values in the graph When the dark end of the brightness bar appears on

the left — as by default when editing an RGB image — colors are measured in

terms of brightness values The colors in the graph proceed from black on the

left to white on the right, as demonstrated in the left example of Figure 17-22

Therefore, higher values produce lighter colors This is my preferred setting

because it measures colors in the same direction as the Levels dialog box

If you click the brightness bar, white and black switch places, as shown in the

second example of the figure The result is that Photoshop measures the

col-ors in terms of ink coverage, from 0 to 100 percent of the primary color Higher

values now produce darker colors This is the default setting for grayscale and

CMYK images

Figure 17-22: Click the brightness bar to change the way in which the graph

measures color: by brightness values (left) or by ink coverage (right)

✦ Curve tools: Use the curve tools to draw the curve inside the brightness

graph The point tool (labeled in Figure 17-23) is selected by default Click in

the graph with this tool to add a point to the curve Drag a point to move it

To delete a point, Ctrl-click it

Brightness values

Ink coverage

The pencil tool lets you draw free-form curves simply by dragging inside thegraph, as illustrated in Figure 17-23 This pencil works much like Photoshop’sstandard pencil tool This means you can draw straight lines by clicking onelocation in the graph and Shift-clicking a different point.

Figure 17-23: Use the pencil tool to draw free-form lines in the brightness

graph If the lines appear rough, you can soften them by clicking on the Smooth button

✦ Input and Output values: The Input and Output values monitor the location

of your cursor in the graph according to brightness values or ink coverage,depending on the setting of the brightness bar You can modify the Input andOutput values when working with the point tool Just click the point on thegraph that you want to adjust and then enter new values The Input number rep-resents the brightness or ink value of the point before you entered the Curvesdialog box; the Output number represents the new brightness or ink value.You can change the Output value also by using the up and down arrow keys.Click the point you want to modify Then press the up or down arrow key toraise or lower the Output value by 1 Press Shift+up or down arrow to changethe Output value in increments of 10 Note that these techniques — and onesthat follow — work only when the point tool is active (You can’t change pointswith the pencil tool.)

When editing multiple graph points from the keyboard, it’s helpful to be able

to activate the points from the keyboard as well To advance from one point

Tip

Pencil toolPoint tool

to the next, press Ctrl+Tab To select the previous point, press Ctrl+Shift+Tab.

To deselect all points, press Ctrl+D

✦ Load/Save: Use these buttons to load and save settings to disk.

✦ Smooth: Click the Smooth button to smooth out curves drawn with the pencil

tool Doing so leads to smoother color transitions in the image window Thisbutton is dimmed except when you use the pencil tool

✦ Auto: Click this button to automatically map the darkest pixel in your

selec-tion to black and the lightest pixel to white Photoshop throws in some tional darkening and lightening according to the Clip percentages, which youcan edit by Alt-clicking on the button

addi-✦ Eyedroppers: If you move the cursor out of the dialog box and into the image

window, you get the standard eyedropper cursor Click a pixel in the image tolocate the brightness value of that pixel in the graph A circle appears in thegraph, and the Input and Output numbers list the value for as long as youhold down the mouse button, as shown in the first example in Figure 17-24

The other eyedroppers work as they do in the Levels dialog box, mapping els to black, medium gray, or white (or other colors if you double-click the eye-dropper icons) For example, the second image in Figure 17-24 shows the whiteeyedropper tool clicking on a light pixel, thereby mapping that value to white,

pix-as shown in the highlighted portion of the graph below the image

Bear in mind that Photoshop maps the value to each color channel dently So when editing a full-color image inside the Curves dialog box, youhave to switch channels to see the results of clicking with the eyedropper Youcan further adjust the brightness value of that pixel by dragging the corre-sponding point in the graph, as demonstrated in the last example of the figure

indepen-The eyedropper tools aren’t the only way to add points to a curve from theimage window Photoshop offers two more keyboard tricks that greatly sim-plify the process of pinpointing and adjusting colors inside the Curves dialogbox Bear in mind, both of these techniques work only when the point tool

is active:

✦ To add a color as a point along the Curves graph, Ctrl-click a pixel in the image

window Photoshop adds the point to the channel displayed in the dialog box

For example, if the RGB composite channel is visible, the point is added to theRGB composite curve If the Red channel is visible, Photoshop adds the point

to the red graph and leaves the green and blue graphs unchanged

✦ To add a color to all graphs, regardless of which channel is visible in the

Curves dialog box, Ctrl+Shift-click a pixel in the image window In the case of

an RGB image, Photoshop maps the red, green, and blue brightness values forthat pixel to each of the red, green, and blue graphs in the Curves dialog box

The RGB composite graph shows no change — switch to the individual nels to see the new point

chan-Tip

Note

Figure 17-24: Use the standard eyedropper cursor to locate a color

in the brightness graph (left) Click with one of the eyedropper tools from the Curves dialog box to map the color of that pixel in the graph (middle) You then can edit the location of the point in the graph by dragging it (right)

Gradient maps

Photoshop has long permitted you to apply a gradation as a Curves map, butVersion 6 makes it easier than ever before Just choose Image ➪ Adjust ➪ GradientMap to display the dialog box pictured in Figure 17-25 Make sure the Preview checkbox is turned on Then click the down-pointing arrowhead to the right of the gradi-ent preview to display the familiar gradient drop-down palette Select a gradientother than Foreground To Background and watch the fireworks

In the psychedelic Color Plate 17-14, I cloned Constantine to a new layer andapplied a heavy dose of Gaussian Blur Then I used the Gradient Map command toapply each of three custom Curves maps In the bottom row, I mixed these fantasticimages with their underlying originals using the Color blend mode

6

Photoshop 6

Figure 17-25: Choose the Gradient Map command to apply

a preset gradient as a Curves map Color Plate 17-14 shows

examples

What’s going on? As foreign as it may sound, any gradient can be expressed as a

Curves graph, progressing through a variety of brightness values in each of the three

(RGB) or four (CMYK) color channels When applied as a gradient map, the

begin-ning of the gradient maps black; the end of the gradient maps white If you apply the

Violet, Orange preset, for example, the dark colors in the image map to violet and

the light colors map to orange Noise-type gradients (introduced in the “Applying

Gradient Fills” section of Chapter 6) produce especially interesting effects

Practical applications: continuous curves

Due to the complex nature and general usefulness of the Curves dialog box, I spend

this section and the next exploring practical applications of its many options,

con-centrating first on the point tool and then on the pencil tool These discussions

assume that the brightness bar is set to edit brightness values, so that the gradation

in the bar lightens from left to right If you set the bar to edit ink coverage — where

the bar darkens from left to right — you can still achieve the effects I describe, but

you must drag in the opposite direction For example, if I tell you to lighten colors

by dragging upward, you would drag downward

When you first enter the Curves dialog box, the brightness curve appears as a

straight line strung between two points, as shown in the first example of Figure 17-26,

mapping every input level from black (the lower-left point) to white (the upper-right

point) to an identical output level If you want to perform seamless color corrections,

the point tool is your best bet because it enables you to edit the levels in the

bright-ness graph while maintaining a continuous curve

Note