Photoshop 6 for Windows Bible- P17 pptx

When you choose Filter ➪ Other ➪ High Pass, Photoshop offers a single option: the familiar Radius value, which can vary from 0.1 to 250.0.. Figure 10-17: The results of separating high-

Figure 10-14: The original Ike is a bit soft (left), a condition I can remedy with

Unsharp Mask Leaving the Threshold value set to 0 brings out the film grain

(middle), but raising the value results in equally unattractive artifacts (right)

While we wait for Photoshop to give us a better Threshold — one with a Fuzziness

slider or similar control — you can create a better Threshold using a very simple

masking technique Using a few filters that I explore at greater length throughout

this chapter and the next, you can devise a selection outline that traces the

essen-tial edges in the image — complete with fuzzy transitions — and leaves the

non-edges unmolested So get out your favorite old vintage photograph and follow

along with these steps

STEPS: Creating and Using an Edge Mask

1 Duplicate one of the color channels Bring up the Channels palette and drag

one of the color channels onto the little page icon Ike is a grayscale image, so

I duplicate the one and only channel

2 Choose Filter ➪ Stylize ➪ Find Edges As I explain in Chapter 11, the Find

Edges filter automatically traces the edges of your image with thick, gooey

outlines that are ideal for creating edge masks

3 Press Ctrl+I Or choose Image ➪ Adjust ➪ Invert Find Edges produces black

lines against a white background, but in order to select your edges, you need

white lines against a black background The Invert command reverses the

lights and darks in the mask, as in the first example in Figure 10-15

Soft

Sharpened, Threshold: 0

Sharpened, Threshold: 20

Figure 10-15: I copy a channel, find the edges, and invert (left) I then apply a

string of filters to expand and soften the edges (middle) After converting the mask to a selection outline, I reapply Unsharp Mask with winning results (right)

4 Choose Filter ➪ Noise ➪ Median You need fat, gooey edges, and the current

ones are a bit tenuous To firm up the edges, choose the Median filter, enter

a value of 2 (or thereabouts), and press Enter

5 Choose Filter ➪ Other ➪ Maximum The next step is to thicken up the edges.

The Maximum filter expands the white areas in the image, serving much thesame function in a mask as Select ➪ Modify ➪ Expand serves when editing aselection outline Enter 4 for the Radius value and press Enter

6 Choose Filter ➪ Blur ➪ Gaussian Blur Unfortunately, the Maximum filter

results in a bunch of little squares that don’t do much for our cause You can merge the squares into a seamless line by choosing the Gaussian Blurcommand and entering 4, the same radius you entered for Maximum Thenpress Enter

The completed mask is pictured in the second example of Figure 10-15.Though hardly an impressive sight to the uninitiated eye, you’re looking

at the perfect edge mask — soft, natural, and extremely accurate

7 Return to the standard composite view Press Ctrl+tilde (~) in a color image.

In a grayscale image, press Ctrl+1

8 Convert the mask to a selection outline Ctrl-click the mask name in the

Channels palette Photoshop selects the most essential edges in the imagewithout selecting the grain

Find Edges, Invert

Find edge mask

Sharpened edges

9 Choose Filter ➪ Sharpen ➪ Unsharp Mask In the last example in Figure 10-15, I

applied the highest permitted Amount value, 500 percent, and a Radius of 2.0

10 Whatever values you use, make sure the Threshold is set to 0 And always

leave it at 0 from this day forward

In case Figures 10-14 and 10-15 are a little too subtle, I include enlarged views of

the great general’s eyes in Figure 10-16 The top eyes show the result of using the

Threshold value, the bottom eyes were created using the edge mask Which ones

appear sharper and less grainy to you?

Figure 10-16: Enlarged views of

the last examples from Figures10-14 (top) and 10-15 (bottom)

A good edge mask beats theThreshold value every time

Using the High Pass filter

The High Pass filter falls more or less in the same camp as the sharpening filters but

is not located under the Filter ➪ Sharpen submenu This frequently overlooked gem

enables you to isolate high-contrast image areas from their low-contrast counterparts

When you choose Filter ➪ Other ➪ High Pass, Photoshop offers a single option:

the familiar Radius value, which can vary from 0.1 to 250.0 As demonstrated in

Figure 10-17, high Radius values distinguish areas of high and low contrast only

slightly Low values change all high-contrast areas to dark gray and low-contrast

areas to a slightly lighter gray A value of 0.1 (not shown) changes all pixels in an

image to a single gray value and is therefore useless

Figure 10-17: The results of separating high- and low-contrast areas in

an image with the High Pass filter set at eight different Radius values

Applying High Pass to individual color channels

In my continuing series of color plates devoted to adding a bit of digital color to theages-old game of chess, Color Plate 10-5 shows the results of applying the High Passfilter set to a Radius value of 5.0 to the various color channels This application is apretty interesting use for this filter When applied to all channels at once, High Pass

has an irritating habit of robbing the image of color in the low-contrast areas, just

where the color is needed most But when you apply it to a single channel, there’s

no color to steal In fact, the filter adds color For example, because there is almost

no contrast in the dark shadows, High Pass elevates the black to gray in each of the

affected color channels The gray in the red channel appears red, the gray in the

red channel mixed with the gray in the green channel appears yellow, and so on

As a result, the filter imbues each image with a chalky glow

I enhanced the High Pass effect slightly in Color Plate 10-5 by increasing the

contrast of each affected color channel using the Levels command Using the

Input option boxes at the top of the Levels dialog box, I changed the first value

to 65 and the third value to 190, thereby compressing the color space equally on

both the black and white sides Had I not done this, the images would appear a

little more washed out (Not a lot, but I figure that you deserve the best color I

can deliver.) For detailed information on the Levels command, read Chapter 17

Converting an image into a line drawing

The High Pass filter is especially useful as a precursor to Image ➪ Adjust ➪ Threshold,

which converts all pixels in an image to black and white (again, covered in Chapter

17) As illustrated in Figure 10-18, the Threshold command produces entirely different

effects on images before and after you alter them with the High Pass filter In fact,

applying the High Pass filter with a low Radius value and then issuing the Threshold

command converts your image into a line drawing

In the second row of examples in the figure, I followed Threshold with Filter ➪

Blur ➪ Gaussian Blur (the subject of the next section) I set the Gaussian Blur

Radius value to 1.0 Like the Threshold option in the Unsharp Mask dialog box,

the Threshold command results in harsh transitions; Gaussian Blur softens

them to produce a more natural effect

Why change your image to a bunch of slightly different gray values and then apply

a command such as Threshold? One reason is to create a mask, as discussed at

length in the “Building a Mask from an Image” section of Chapter 9 (In Chapter 9, I

used Levels instead of Threshold, but both are variations on the same theme.)

You might also want to bolster the edges in an image For example, to achieve the

last row of examples in Figure 10-18, I layered the images prior to applying High

Pass, Threshold, and Gaussian Blur Then I monkeyed around with the Opacity

setting and the blend mode to achieve an edge-tracing effect

I should mention that Photoshop provides several automated edge-tracing filters —

including Find Edges, Trace Contour, and the Gallery Effects acquisition, Glowing

Edges But High Pass affords more control than any of these commands and permits

you to explore a wider range of alternatives Also worth noting, several Gallery

Effects filters — most obviously Filter ➪ Sketch ➪ Photocopy — lift much of their

code directly from High Pass Although it may seem at first glance a strange effect,

High Pass is one of the seminal filters in Photoshop

Note

Note

Figure 10-18: Several applications of the High Pass filter with low

Radius values (top row), followed by the same images subject to Image ➪ Adjust ➪ Threshold and Filter ➪ Blur ➪ Gaussian Blur (middle)

I then layered the second row onto the first and modified the Opacity and blend mode settings to create the third row

Threshold and Gaussian Blur

Opacity: 45%, Overlay mode

Blurring an Image

The commands under the Filter ➪ Blur submenu produce the opposite effects of

their counterparts under the Filter ➪ Sharpen submenu Rather than enhancing the

amount of contrast between neighboring pixels, the Blur filters diminish contrast to

create softening effects

Applying the Gaussian Blur filter

The preeminent Blur filter, Gaussian Blur, blends a specified number of pixels

incre-mentally, following the bell-shaped Gaussian distribution curve I touched on earlier

When you choose Filter ➪ Blur ➪ Gaussian Blur, Photoshop produces a single Radius

option box, in which you can enter any value from 0.1 to 250.0 (Beginning to sound

familiar?) As demonstrated in Figure 10-19, Radius values of 1.0 and smaller blur an

image slightly; moderate values, between 1.0 and 5.0, turn an image into a rude

approximation of life without my glasses on; and higher values blur the image

beyond recognition

Moderate to high Radius values can be especially useful for creating that hugely

amusing Star Trek Iridescent Female effect This is the old Star Trek, of course.

Captain Kirk meets some bewitching ambassador or scientist who has just beamed

on board He takes her hand in sincere welcome as he gives out with a lecherous

grin and explains how truly honored he is to have such a renowned guest in his

transporter room, and so charming to boot Then we see it — the close-up of the

fetching actress shrouded in a kind of gleaming halo that prevents us from

discern-ing if her lips are chapped or perhaps she’s hiddiscern-ing an old acne scar, because some

cockeyed cinematographer smeared Vaseline all over the camera lens I mean, what

wouldn’t you give to be able to recreate this effect in Photoshop?

Unfortunately, I don’t have any images of actresses adorned in futuristic go-go

boots, so Constantine cum Rambo will have to do in a pinch The following steps

explain how to make the colossal head glow as demonstrated in Figure 10-20

STEPS: The Captain Kirk Myopia Effect

1 Press Ctrl+A to select the entire image If you only want to apply the effect to

a portion of the image, feather the selection with a radius in the neighborhood

of 5 to 8 pixels

2 Choose Filter ➪ Blur ➪ Gaussian Blur Enter some unusually large value into

the Radius option box — say, 8.0 — and press Enter

3 Press Ctrl+Shift+F to bring up the Fade dialog box To achieve the effects

shown in Figure 10-20, I reduced the Opacity value to 70 percent, making the

blurred image slightly translucent This way, you can see the hard edges of

the original image through the filtered one

4 You can achieve additional effects by selecting options from the Mode pop-up menu For example, I created the upper-right example in the figure

by selecting the Screen option, which uses the colors in the filtered image

to lighten the original I created the two bottom examples in the figure byapplying the Darken and Lighten options

Figure 10-19: The results of blurring an image with the Gaussian Blur

filter using eight different Radius values, ranging from slightly out of focus to Bad Day at the Ophthalmologist’s Office

Figure 10-20: After blurring the image, I chose Edit ➪ Fade

Gaussian Blur and changed the Opacity value to 70 percent

Then I applied the labeled blend modes to alter the image further

Color Plate 10-6 shows an image that’s more likely to interest Captain Kirk It

shows a young agrarian woman subject to most of the same settings I applied

earlier to Constantine Again, I applied the Gaussian Blur filter with a Radius of 8.0

Then I used Edit ➪ Fade Gaussian Blur to adjust the Opacity value and blend mode

The upper-left image shows the Normal mode, but the upper-right image shows

the Luminosity mode In this case, the Screen mode resulted in a washed-out effect,

whereas Luminosity yielded an image with crisp color detail and fuzzy brightness

values As a result, there are some interesting places where the colors leap off her

checkered dress As in Figure 10-20, the bottom two images show the effects of the

Darken and Lighten modes

You know, though, as I look at this woman, I’m beginning to have my doubts about

her and Captain Kirk I mean, she has Scotty written all over her

The preset blurring filters

Neither of the two preset commands in the Filter ➪ Blur submenu, Blur and BlurMore, can distribute its blurring effect over a bell-shaped Gaussian curve For thatreason, these two commands are less functional than the Gaussian Blur filter.However, just so you know where they stand in the grand Photoshop focusingscheme, Figure 10-21 shows the effect of each preset command and the nearlyequivalent effect created with the Gaussian Blur filter

Figure 10-21: The effects of the

two preset blurring filters (top row)compared with their Gaussian Blurequivalents (bottom row), whichare labeled according to Radiusvalues

Antialiasing an image

If you have a particularly jagged image, such as a 256-color GIF file, there’s a better way to soften the rough edges than applying the Gaussian Blur filter Thebest solution is to antialias the image How? After all, Photoshop doesn’t offer anAntialias filter Well, think about it Back in the “Softening selection outlines” section

of Chapter 8, I described how Photoshop antialiases a brushstroke or selection outline at twice its normal size and then reduces it by 50 percent and applies bicubic interpolation You can do the same thing with an image

Choose Image ➪ Image Size and enlarge the image to 200 percent of its present size.Make sure that the Resample Image check box is turned on and set to Bicubic (Youcan also experiment with Bilinear for a slightly different effect, but don’t use Nearest

Neighbor.) Next, turn right around and choose Image ➪ Image Size again, but this

time shrink the image by 50 percent

The top-left example in Figure 10-22 shows a jagged image subject to this effect I used

Image ➪ Adjust ➪ Posterize to reduce Moses to four colors It’s ugly, but it’s not unlike

the kind of images you may encounter, particularly if you have access to an aging

image library To the right is the same image subject to Gaussian Blur with a very

low Radius value of 0.5 Rather than appearing softened, the result is just plain fuzzy

Figure 10-22: A particularly jagged image (top left) followed by the image

blurred using a filter (top right) By enlarging and reducing the image one or

more times (bottom left and right), I soften the pixels without making them

appear blurry The enlarged details show each operation’s effect on the

individual pixels

Jagged original Gaussian Blur, 0.5

Antialiased Antialiased x 4

However, if I instead enlarge and reduce the image with the Image Size command,

I achieve a true softening effect, as shown in the lower-left example in the figure,commensurate with Photoshop’s antialiasing options Even after enlarging andreducing the image four times in a row — as in the bottom-right example — I don’t make the image blurry, I simply make it softer

Directional blurring

In addition to its everyday blurring functions, Photoshop provides two directional

blurring filters, Motion Blur and Radial Blur Instead of blurring pixels in feathered

clusters like the Gaussian Blur filter, the Motion Blur filter blurs pixels in straightlines over a specified distance The Radial Blur filter blurs pixels in varying degreesdepending on their distance from the center of the blur The following pages explainboth of these filters in detail

Motion blurring

The Motion Blur filter makes an image appear as if either the image or camera was moving when you shot the photo When you choose Filter ➪ Blur ➪ Motion Blur, Photoshop displays the dialog box shown in Figure 10-23 You enter the angle

of movement into the Angle option box Alternatively, you can indicate the angle

by dragging the straight line inside the circle on the right side of the dialog box,

as shown in the figure (Notice that the arrow cursor actually appears outside thecircle Once you begin dragging on the line, you can move the cursor anywhere you want and still affect the angle.)

Figure 10-23: Drag the line inside the circle to

change the angle of the blur

You then enter the distance of the movement in the Distance option box Photoshop

permits any value between 1 and 999 pixels The filter distributes the effect of

the blur over the course of the Distance value, as illustrated by the examples

in Figure 10-24

Figure 10-24: A single black rectangle followed by five different

applications of the Motion Blur filter Only the Distance value varied,

as labeled A 0-degree Angle value was used in all five examples

Mathematically speaking, Motion Blur is one of Photoshop’s simpler filters Rather

than distributing the effect over a Gaussian curve — which one might argue would

produce a more believable effect — Photoshop creates a simple linear distribution,

peaking in the center and fading at either end It’s as if the program took the value

you specified in the Distance option, created that many clones of the image, offset

half the clones in one direction and half the clones in the other — all spaced 1 pixel

apart — and then varied the opacity of each

Using the Wind filter

The problem with the Motion Blur filter is that it blurs pixels in two directions Ifyou want to distribute pixels in one absolute direction or the other, try the Wind filter, which you can use either on its own or in tandem with Motion Blur

When you choose Filter ➪ Stylize ➪ Wind, Photoshop displays the Wind dialog boxshown in Figure 10-25 You can select from three methods and two directions to distribute the selected pixels Figure 10-26 compares the effect of the Motion Blurfilter to each of the three methods offered by the Wind filter Notice that the Windfilter does not blur pixels Rather, it evaluates a selection in 1-pixel-tall horizontalstrips and offsets the strips randomly inside the image

Figure 10-25: Use the Wind filter

to randomly distribute a selection

in 1-pixel horizontal strips in one

of two directions

To get the best results, try combining the Motion Blur and Wind filters with a cent selection For example, to create Figure 10-27, I cloned the entire image to a newlayer and applied the Wind command twice, first selecting the Stagger option andthen selecting Blast Next, I applied the Motion Blur command with a 0-degree angleand a Distance value of 30 I then set the Opacity option in the Layers palette to 80percent and selected Lighten from the blend mode pop-up menu

translu-The result is a perfect blend between two worlds translu-The motion effect in Figure 10-27

doesn’t obliterate the image detail, as the Wind filter does in Figure 10-26 And the

motion appears to run in a single direction — to the right — something you can’t

accomplish using Motion Blur on its own

Figure 10-26: The difference between the effects of the Motion

Blur filter (upper left) and the Wind filter (other three) In each

case, I selected From the Right from the Direction radio buttons

Radial blurring

Choosing Filter ➪ Blur ➪ Radial Blur displays the Radial Blur dialog box shown in

Figure 10-28 The dialog box offers two Blur Method options: Spin and Zoom