Photoshop CS4 Studio Techniques- P6 doc

When you adjust the image, the Curves dialog automatically sets itself to work on the Lightness information, which prevents the adjustment from shifting the color of the image and makes

First, you can apply Curves to the active layer by choosing Image > Adjustments > Curves Immediately after apply-ing Curves, you can choose Edit > Fade Curves and set the

Mode pop-up menu to Luminosity (Figure 3.108) The

Fade command limits the last change you made (Curves,

in this case) to changing only the brightness of the image

(Luminosity is just another word for brightness.) It won’t shift

the colors or change how saturated they are

Your other choice would be to apply Curves to more than one layer by clicking the Curves icon in the Adjustments panel Then you can change the blending mode in the

Layers panel to Luminosity (Figure 3.109) An adjustment

layer affects all the layers below it but none of the layers above it It’s also a nonpermanent change, because you can double-click the adjustment layer thumbnail in that layer

to reopen the Curves dialog and make changes fore, any Curves techniques you use for adjusting grayscale images will work on color images if you use the Luminosity

There-blending mode (Figure 3.110).

Figure 3.110 With a Curves adjustment layer, you can make non-destructive changes to an image.

Color shifts aren’t the only problems you’ll encounter when adjusting color images with Curves The mode your image is in might have an adverse effect on the adjustment RGB color images are made from three components (red, green, and blue) A bright green color might be made out

Figure 3.108 Choose Edit > Fade

Curves to limit changes to the

bright-ness of the image.

Figure 3.109 You can quickly apply a

Curves adjustment as a separate layer

by clicking in the Adjustments panel.

Curves dialog, the pop-up menu at the top of the dialog is

set to RGB, which will cause any points to affect the same

R, G, and B values Clicking that green color in the image

displays a circle at 165 on the curve, which will affect all

the areas that contain 165 red, 165 blue, and 165 green

Equal amounts of R, G, and B create gray Simply clicking

the curve of a color image usually causes the colors to shift

in an unsatisfactory way, because the circle that appears

when clicking the image will not accurately target the area

you clicked

While working in RGB mode, all color areas shift because

their RGB mix changes as the Curves dialog shifts the RGB

values in equal amounts Ideally it would affect only the

exact mix of RGB from which the color is made, but Curves

doesn’t work that way in RGB mode The solution to this

problem is to convert the image to LAB mode by

choos-ing Image > Mode > Lab Color In LAB mode, the image is

made from three components: Lightness, A, and B When

you adjust the image, the Curves dialog automatically sets

itself to work on the Lightness information, which prevents

the adjustment from shifting the color of the image and

makes the circle show up in the correct position for accurate

adjustments When you’re done with the adjustment, you

should convert the image back to RGB mode, because many

of Photoshop’s features are not available in LAB mode You

may not use LAB mode for every color image; reserve it for

those images that are troublesome in RGB mode

Quick Recap

To verify that you’re ready to move on, make sure that you

understand the general concepts of Curves:

Flattening a curve reduces contrast and makes it more

diffi cult to see detail

Making a curve steeper increases contrast and makes it

easier to see detail

In the 0–100% system, up means darker and down

means brighter

In the 0–255 system, up means brighter and down

means darker

The word LAB in LAB mode is an

acronym for what color channels it controls: Lightness, A, and B Don’t say “lab,” say the letters: “L-A-B mode.”

The Histogram Panel

Used properly, the histogram that’s displayed behind the curve in the Curves dialog can help you to make sure that your adjustments don’t get out of control and end up harming your images instead of improving them Photo-shop’s Histogram panel also can help you to ensure that you don’t push your edits and adjustments too far Now that you have an idea of how to think about Curves, let’s

fi gure out how to use these two tools to help with edits To display the Histogram panel, choose Window > Histogram

As you learned earlier, a histogram is a simple bar graph that shows the range of brightness levels that make up an image and the prevalence of each of these shades When you look at the histogram, imagine that a gradient is stretched across the bottom of the bar graph, with black on the left and white on the right just as in the Curves dialog

(Figure 3.111) If the histogram shows a bar above a

par-ticular shade of gray, that shade is used somewhere in the image If there’s no bar, that brightness level isn’t used in that image The height of the bar indicates how prevalent

a particular brightness level is compared to the others that make up the image

The Histogram panel shows the same histogram but with a bonus When you start to adjust an image, the Histogram panel overlays a histogram that represents the current, adjusted state of the image (black) above the original his-togram that shows what the image looked like before you

started adjusting it (gray), as shown in Figure 3.112.

Achieving Optimal Contrast

If the histogram doesn’t extend all the way from black

to white, the image has a limited brightness range

(Figures 3.113 and 3.114) When that’s the case, you can

usually move the upper-right and lower-left points on a curve toward the middle, which will widen the histogram

(Figure 3.115) As you do, keep an eye on the histogram

Most images will look their best when the histogram extends all the way across the area available, without pro-

Figure 3.111 Imagine a gradient at

the bottom of the Histogram panel.

Figure 3.112 The gray histogram

reflects the unadjusted image; the

black version reflects the adjusted

image.

Figure 3.113 An image with limited

brightness (©2008 Dan Ablan.)

Figure 3.115 The result of applying the curve to the image.

Two controls make this edit a little simpler Notice that

below the grayscale ramp beneath the curve are sliders for

black point and white point, just like the one in the Levels

dialog Moving these sliders is the same as adjusting the

points on the end of the curve

Preventing Blown-Out Highlights and Plugged-Up Shadows

Because the height of the bars in the histogram indicates

how prevalent each shade is within the image, tall spikes

on the ends of the histogram indicate that the image

contains large quantities of white or black (Figure 3.116).

That’s usually an indication of a lack of detail in the

bright-est or darkbright-est areas of the image If the image contains

shiny areas that refl ect light directly into the camera (shiny

metal or glass, for instance), it’s okay if those areas end up

with no detail But if that’s not the case, part of the curve

must have topped or bottomed out You should think

about moving that area of the curve away from the top or

bottom so you can get back the detail that was originally in

that part of the image (Figure 3.117).

The Histogram panel can be used

in two different sizes—Compact

or Expanded The Expanded version

is exactly 256 pixels wide; most images contain 256 shades of gray, which makes the Expanded version

of the histogram the most accurate histogram for the image You can switch between the two different views on the side menu of the Histogram panel.

Figure 3.116 This histogram indicates

a lot of black in the image because the slope is heavier on the left.

Figure 3.117 After an adjustment, the histogram shows less black and a more even shape.

Avoiding Posterization

If the histogram in the Histogram panel is showing gaps

that make it look like a comb (Figure 3.118), keep an eye

on the brightness levels directly below that area of the histogram Gaps in a histogram indicate that certain bright-ness levels are not found in the image, which can indicate

posterization (stair-stepped transitions where there would

usually be a smooth transition), as in Figure 3.119 That

usually happens when you make part of a curve rather steep As long as the gaps are small (two to three pixels wide), it’s not likely that you’ll notice it in the image If the gaps get much wider than that, you might want to inspect the image and think about making the curve less steep The histogram in the Curves dialog doesn’t show these gaps, because it only shows the original, unedited histogram

Figure 3.118 A histogram that looks

like this might indicate that the image

is posterized.

Figure 3.119 The posterized image based on the histogram in Figure 3.118.

To better understand posterization, try this: Create a new grayscale document, press D to reset the foreground and background colors to black and white, and then click and drag across the document with the Gradient tool While watching the Histogram panel, choose Image > Adjustments > Posterize and experiment with different settings—the gaps don’t have to be very wide before you

notice posterization (Figure 3.120).

Figure 3.120 Posterize a grayscale image to get a sense of how wide the gaps can be before you see posterization

in an image.

You can minimize posterization by working with 16-bit

images Unlike standard 8-bit images that are made from

256 shades of gray (or 256 shades each of red, green, and

blue), 16-bit images contain up to 32,767 shades of gray

You can obtain 16-bit images from RAW format digital

camera fi les when opening them in the Camera Raw dialog

(see Chapter 4, “Using Camera Raw 5.0,” for more details),

or from some newer fl atbed or fi lm scanners You can tell

that you’re working with a 16-bit fi le by looking at the title

bar for the image After the fi lename, you should see

some-thing like (RGB/16), which indicates that you have a 16-bit

RGB-mode image

The Histogram panel usually builds its histogram by

analyz-ing an 8-bit cached image, just to make sure that the panel

display updates quickly A cached image is a smaller version

of the image with 8 bits of information If you notice the

“comb” look when adjusting a 16-bit image (Figure 3.121),

look for the warning triangle near the upper right of the

If you notice slight posterization in the image, you might apply a little bit of noise to it (Filter > Noise >

Add Noise, Amount: 3, Gaussian), which should make it less notice- able If that doesn’t do the trick, check out the manual method for eliminating posterization described

in Chapter 7.

histogram That indicates that the histogram is being created from a lower-resolution 8-bit image Clicking the triangle causes the histogram to be redrawn directly from the high-resolution 16-bit fi le, which should eliminate the comb look and therefore indicate that the image isn’t

really posterized (Figure 3.122).

Figure 3.121 This histogram indicates that the image might be posterized.

Figure 3.122 The uncached gram is a more accurate view of the image.

histo-Sneaky Contrast Adjustments

Flattening a curve is usually harmful to an image because the detail in the area you’re adjusting will be very diffi cult

to see Often you can cheat, however, by analyzing the histogram to determine which areas of an image won’t be harmed by fl attening the curve Because short lines in a histogram indicate shades that are not very prevalent in the image, those areas usually can be fl attened in a curve without noticeable degradation to the image Flattening one part of the curve allows you to make the rest of the curve steeper, increasing contrast in those areas and mak-ing the area appear to have more detail

When you see a fl at area of the histogram in the Curves dialog, place two points on the curve, one at each end

of the fl at section of the histogram Here’s how it works: While you’re in the Curves dialog, glance over at the Histo-gram panel and look for short, fl at areas When you fi nd a

fl at area (not all images have them), choose Show Statistics from the side menu of the Histogram panel, and then click and drag across that area in the Histogram panel, but

don’t release the mouse button (Figure 3.123) Look at the

Level numbers that show up just below the histogram (if

Figure 3.123 Show statistics for the

histogram and drag across an area.

you don’t see any numbers under the histogram, choose

Expanded View from the side menu of the Histogram

panel) Next, release the mouse button and move your

cur-sor around the Curves dialog to see whether the numbers

at the bottom are 0–100% or 0–255 numbers If they range

from 0–100%, click the Curve Display Options button

and change the Show Amount Of setting to switch to the

0–255 numbering system Now click in the middle of the

curve and change the numbers that appear in the Input

and Output fi elds at the bottom of the Curves dialog to

the fi rst number you saw in the Histogram panel (Figure

3.124) Add a second point and do the same for the second

number you saw in the Histogram panel Move the upper

dot straight down and the lower dot straight up until the

area between the two becomes almost horizontal (Figure

3.125) Keep an eye on the image as you do this, to see how

fl at you make the line without screwing up the image That

should increase the contrast across most of the image while

reducing contrast in those brightness levels that are not

very prevalent in the image

Just because we’ve talked about the Histogram panel here

in the Curves chapter, that doesn’t mean that you use it

only when making Curves adjustments The Histogram

panel is useful for performing any type of adjustment and

for analyzing an image to determine what types of

adjust-ments you might need to consider Many professional

cam-eras offer a histogram view, and the principles are the same

In general, you shouldn’t adjust images based solely on

what the histogram is showing Instead, adjust the image

until you like its general appearance, and then look at the

Histogram panel for signs that you might have gone too

far If you notice spikes on the ends or a huge comb taking

shape, take a closer look at the image to determine if it’s

worth backing off from the adjustment Who cares what

the histogram looks like in the end? The visual look of

your image is more important The histogram is just like

that seatbelt warning light in your car—you can ignore it,

but there’s a reason it’s on

Figure 3.125 Add a second point and adjust to flatten out the curve.

Figure 3.124 Click in the curve and enter the value from the histogram.

If an image needs more pronounced shadows and/or highlight detail, the Shadows/Highlights command (Image > Adjustments > Shadows/Highlights) is a good

alternative to Curves (Figure 3.126) In its simplest form,

you just move the Shadows slider to brighten the darker

areas of the image (Figures 3.127 and 3.128) and/or move the Highlights slider to darken the brighter areas (Figures

Figure 3.126 The Shadows/Highlights

command is a good alternative to

Curves.

Figure 3.129 The original image (©2008 Dan Ablan.)

Figure 3.130 The Highlights slider darkens brighter areas of the image.

If you need more control over the adjustment, click the

Show More Options check box to see the full range of

set-tings available (Figure 3.131) Start by setting Amount to

0%, Tonal Width to 50%, and Radius to 30px in both the

Shadows and Highlights areas of the dialog The Amount

setting determines how radical a change you’ll make to

the image Because you’re starting with that setting at zero,

these settings won’t do a thing to the image—yet

If you want to pull out some detail in the dark areas of

an image, move the Amount slider in the Shadows area

toward the right while you watch the image Keep moving it

until the dark areas of the image reach the desired

bright-ness Now start changing the Tonal Width setting, which Figure 3.131 more advanced controls when needed.The Shadows/Highlights dialog offers

controls the brightness range in the image Extremely low settings limit the adjustment to the darkest areas of the image; higher settings allow the adjustment to creep into

the brighter areas of the image (Figures 3.132 and 3.133).

The Shadows/Highlights command adjusts areas based on the brightness level of the surrounding image So, once you’ve defi ned the brightness range you want (via the Tonal Width slider), you’ll need to experiment with the Radius slider That setting determines how much of the surround-ing image Photoshop uses when determining how to blend the changes you’re making into the surrounding image Just slide it around until the changes to the dark areas of the image look appropriate considering their surround-ings Moving the slider toward the right will cause the area you’re adjusting to blend into the surrounding image more, whereas moving it to the left causes a more pronounced dif-ference between the shadows and midtones of the image When you’ve fi nished your fi rst round with the settings, you’ll most likely want to go back to the Amount and Tonal Width settings to fi ne-tune the result

Figure 3.133 The image from Figure 3.132 after shadow and tonal adjust- ments.

Figure 3.132 The original image

(©2008 Dan Ablan.)

If you’re having trouble seeing

exactly what an adjustment is

doing to an image, experiment

with an extremely simple image

until you get the hang of it Try it

on a new grayscale image to which

you’ve applied a gradient.

The Highlights adjustments work just like the Shadows

adjustments, but attempt to darken the brightest areas of

the image to exaggerate the detail in that area

When you brighten the shadows or darken the highlights,

you’ll often exaggerate any color that was lurking in those

areas (Figures 3.134) If the color is a little too distracting,

try moving the Color Correction slider toward the left to

make the areas you’ve adjusted less colorful (Figure 3.135).

On the other hand, if you’d like to make those areas even

more colorful, move the slider toward the right The

default setting is +20, which is a good starting point

When the brightness and color look good, you’ll need to

fi ne-tune the contrast in the areas of the image that you

haven’t changed You can do that by moving the Midtone

Contrast slider to the left (to lower contrast) or right (to

Figure 3.134 By brightening shadows, you might enhance colors (©2008 Dan Ablan.)

Figure 3.135 Bring the Color tion slider to the left to pull out the color within the image.

Correc-increase contrast) There aren’t any set rules for using these sliders Your image is your guide.

Darkening the highlights on some images can make them look rather dull, especially when working with something that contains shiny objects For something to look truly shiny, the brightest areas of the image (usually direct refl ections of light into the camera lens) need to be pure white If it’s not white, you get just a dull image If you notice those bright refl ections becoming darker when you adjust the Highlights setting, adjust the White Clip setting

at the bottom of the Shadows/Highlights dialog With White Clip set to zero, Photoshop is capable of darkening all the bright areas of the image As you raise that setting, Photoshop forces a narrow range of the brightest shades

in the image to pure white The higher the setting, the wider the range of shades that Shadows/Highlights forces

to white Just watch the image and increase the White Clip setting until those shiny refl ections look nice and bright.The Black Clip setting forces the darkest areas of the image

to black to make sure that they won’t be lightened when you move the Amount setting in the Shadows section of the dialog That change can be useful if you want high-contrast shadow areas or if you have text or other line art that wouldn’t look right lightened

The Next Step

I hope that you’ve come to the conclusion that layers and Curves really aren’t such brain twisters And if you come out of this chapter thinking of ways you might use these features in the future, even better Layers and Curves are among a handful of things that separate the experts from everyone else But there’s no reason why you can’t propel yourself into the expert category Get in the habit

of keeping an eye on the Histogram panel (don’t just use

it with Curves) and spend some time working with the Shadows/Highlights dialog These tools give you that extra bit of versatility and control that can make a big differ-ence with your next image adjustment The initial learning

The Shadows/Highlights command

cannot be used as an adjustment

layer because it’s too complex an

adjustment Adjustment layers are

limited to things that can take any

input (any shade of gray or color)

and know what to do with it

with-out having to know how the rest of

the image looks Because Shadows/

Highlights compares the area you’re

adjusting to its surroundings, it’s

not simple enough to be

imple-mented as an adjustment layer.

Using Camera Raw 5.0

that I can borrow.

—Woodrow Wilson

Using Camera Raw 5.0

It has been an ongoing dilemma for digital phers in recent years: JPG or raw? Some might say that only high-end photographers with high-end gear (read:

photogra-“expensive”) could afford to shoot raw, in all forms of the word But raw-format photography is now a fairly com-mon technique used by photographers of all skill levels

to ensure maximum image quality and a higher level of editing latitude Raw fi les are different from JPEG or TIFF images in that they contain all the data that was captured from the camera, but with minimal processing Many digi-tal cameras today shoot raw—even small pocket cameras For this reason, understanding how to process raw fi les is more important than ever so you can properly evaluate your workfl ow

What Is Raw Format?

Your digital camera has to do quite a bit of processing to turn the raw data from your camera into a JPEG or TIFF

fi le It must interpolate color, adjust for white balance, correct gamma, convert to a color profi le, sharpen, and perform saturation and other adjustments before fi nally compressing the fi le into a JPEG image Think of a raw

fi le as the pure data that comes from the camera’s sor Many image editors can open raw images on both PC and Mac, but occasionally raw formats won’t communi-cate This situation leaves you frustrated and stuck with a