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Chapter 5: Color Correction in the CMYK Color Space: Expert Mode

5-1

P

owerColor’s selective separator offers two color control modes for your image
correction work in the CMYK color space: Production and Expert. The

Production color control mode is discussed in Chapter 4. This chapter explains how
to use Expert mode and covers the following topics:

•

Calibrating PowerColor selective separator

•

Setting up the gray balance

•

Controlling dot gain

•

Using tone controls

•

Setting highlight and shadow

•

Using gradation controls

For information on how to use the CMYK Probe, see 

Understanding the CMYK

Probe 

in Chapter 4.

Calibrating PowerColor Press

CAUTION: PowerColor Press should be set up
and calibrated only using the procedures in this
section. Do not make any adjustments in the
CMYK Setup window.

Understanding Calibration

PowerColor incorporates a user-friendly method of calibrating the CMYK
Separator for specific output devices, such as inkjet printers, conventional proof
printers, and printing presses. The software includes a file called PowerColor 16,
which contains patches for saturated and pastel colors, as well as a three-color
and four-color Black patch (see Figure 5–1). The markers A, B, and C outside the
color patches identify the orientation of the target and the location of the patches.

Содержание PowerColor

Страница 1: ...cumentation xiii Chapter 1 Installation Configuration Requirements 1 1 Host Computer 1 1 Scanner 1 1 Setting Up and Installing PowerColor 1 2 Installing on an Apple Macintosh 1 2 Configuring Your Moni...

Страница 2: ...Images and Memory 2 10 Region Names 2 11 Working with Regions 2 12 Activating Regions 2 12 Adjusting the Queue Manager Window 2 13 Manipulating Regions in the Queue Manager 2 14 Saving the Queues 2 1...

Страница 3: ...Setting Highlight and Shadow 3 4 Using the Gray Eyedropper 3 7 Adjusting Tonal Range in Basic Mode 3 8 Adjusting Tonal Range in Expert Mode 3 10 Using the RGB Controls 3 12 Adjusting Colors 3 12 Corr...

Страница 4: ...rrections 4 2 Selecting Fixed Reference Points 4 3 Using Production Color Controls 4 4 Production Mode Workflow 4 4 Setting Highlight and Shadow Points 4 6 Setting Dot Limits 4 9 Setting an Image s To...

Страница 5: ...alance Table 5 6 Controlling Dot Gain 5 7 Setting Dot Gain 5 7 Using Tone Controls 5 10 Removing Color Casts 5 10 Tone Curves 5 11 Using the Gray Eyedropper 5 12 Setting Highlight and Shadow Points 5...

Страница 6: ...tions 6 6 Customizing the Descreening Function 6 7 Chapter 7 Scanning Images to Disk Reviewing Scan Settings 7 1 Checking Toolbar Parameters 7 2 Scan Type 7 3 Scan Mode 7 3 Line Screen 7 4 Sampling 7...

Страница 7: ...Preface...

Страница 8: ......

Страница 9: ...itial scanning process without additional prescanning PowerColor also provides instant CMYK feedback on your image transformations so you can see the results of your changes immediately For performing...

Страница 10: ...MYK separator based on a density to dot color engine This software is intended for use by those who understand the concepts behind color separation and reproduction as they relate to offset printing P...

Страница 11: ...ographical conventions are used throughout this guide Menus and menu options dialog box selections on screen messages and key board keys appear in bold e g Manual Update Preview etc Note Notes provide...

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Страница 13: ...Installation 1 1...

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Страница 15: ...ing minimum requirements Macintosh Macintosh PowerPC 8100 computer or better with floating point coproces sor installed 24 bit color display adapter 17 or larger high resolution monitor 1024 x 768 dpi...

Страница 16: ...a computer running Microsoft Windows turn to page 1 6 Configuring Your Monitor for PowerColor PowerColor Needs to run in 24 or 32 bit color mode To configure your monitor for PowerColor follow the st...

Страница 17: ...tware To install the PowerColor software proceed as follows 1 Insert the PowerColor CD into your CD ROM drive and double click on the Installer icon 2 Click on Continue in the PowerColor installer spl...

Страница 18: ...change the location in which PowerColor will be installed follow these steps Click on the Install Location drop down menu Choose Select Folder in the drop down menu In the destination window that app...

Страница 19: ...time you launch it Assigning Memory to PowerColor To increase the amount of memory assigned to PowerColor proceed as follows 1 Select the PowerColor application icon in the PowerColor folder and choos...

Страница 20: ...om the pop up window that appears 2 The Windows Display Properties window will appear Choose the Settings Tab 3 In the Color Palette section of the Settings window choose 24 bit or 32 bit color Instal...

Страница 21: ...Getting Acquainted 2 2...

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Страница 23: ...icrosoft Windows interface including drop down menus multiple windows point and click con trols and keyboard shortcuts This chapter covers the following topics Overview of the scanning process Launchi...

Страница 24: ...e verifying the results visually and numerically on screen 4 Scan the final images to disk using the desired output and file formats Launching PowerColor To launch the application double click on the...

Страница 25: ...ting the desired radio button PowerColor Photo This section allows you to set the mode of operation as well as the type of information to be displayed in the expert tone graph PowerColor Press This se...

Страница 26: ...ut also require con siderably more RAM as reflected in the non editable Buffer Size field If you have over 64 MB of RAM available for PowerColor setting the resolu tion to 75 or 100 increases the defa...

Страница 27: ...earest neighbor interpolation by pixel replication should only be used for line art Maximum Optical Resolution This feature allows PowerColor to set a maximum optical scanning resolution for certain f...

Страница 28: ...enter the new gamma value in the Monitor Setup window PowerColor then adjusts its previews to look the same regardless of any monitor gamma in the range of 0 2 to 5 0 Note PowerColor does not adjust...

Страница 29: ...graphs or prints 3 Click on the Preview button in the toolbar or the Preview button below the blank first image in the Queue Manager Your scanner now produces a low resolution overview scan of the ent...

Страница 30: ...ew again hold down the Option key Macintosh or Control key Windows while clicking on the image with the Zoom tool Note The point where the Zoom tool is clicked becomes the new center of the image in t...

Страница 31: ...region also carries its own history list of all actions taken by the user on that region You can scroll the history list by selecting the H icon at the bottom of the region window Macintosh ver sion...

Страница 32: ...eManager Images and Memory The amount of memory RAM required for a region varies depending on the Overview resolution selected in the Preferences window and the size of the region You can create as ma...

Страница 33: ...e region number in the order of its placement in the Queue Manager an arbitrary sequential number Your regions may represent separate originals for different jobs or different areas from within the sa...

Страница 34: ...Switch between detail view and full preview This section explains how to manipulate regions using the Queue Manager Scanning to disk is discussed in Chapter 7 Activating Regions To activate a region...

Страница 35: ...ess M on a Macintosh or Control M on a Windows PC To expand the window to its full size click on the window resize box To resize the Queue Manager window to a custom size click and drag the resize but...

Страница 36: ...ion from the queue activate the region by double clicking on it a red frame appears around it and click on the black Cut button in the Queue Manager to delete the region Cut All To delete all regions...

Страница 37: ...e Manager During scanning the region s Preview button appears red green and blue Once the preview is complete the button turns all red Preview All PowerColor s Preview All button allows you to batch p...

Страница 38: ...d side under the Overview in the Queue Manager Clicking on this icon toggles the scanning process on or off Transforming Images To make your work with regions easier PowerColor also includes the tools...

Страница 39: ...comes a cross hair 3 Click on the center of the desired area of the image to be viewed in detail The scanner now performs a detail scan of predefined dimensions around the point you selected using the...

Страница 40: ...cking changes incrementally However it can add production time due to the time needed to refresh the screen image after every adjustment Updating Manually With automatic updating off click on the Manu...

Страница 41: ...to those in the original prescan To use this feature select one of the options in the Settings menu Save This option allows you to save custom correction settings After adjusting the settings you want...

Страница 42: ...ult settings Note The Save Default option overwrites PowerColor s default settings Once PowerColor s defaults have been overwritten they cannot be recalled If you use certain set tings regularly save...

Страница 43: ...ize This option will reset tone and gradation curves to linear values For other settings it will remove any correction made to the tool For example gray balance would become equal percentages for all...

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Страница 45: ...Correcting Images with PowerColor Photo RGB Mode 3 3...

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Страница 47: ...e cor rections This chapter explains how to use the RGB tools and covers the following topics Using the RGB Probe Using the RGB Controls in Basic Mode Using the RGB Controls in Expert Mode The Photo m...

Страница 48: ...e values for the pixel s at the current cursor position The RGB Probe window is a static display Its appearance depends on the Scan Mode you select in the Control Bar see next section However the Prob...

Страница 49: ...tion see Figure 3 2 When scanning line art the Scan Mode is set to one of the Line options the Line Art Pixel Value field in the RGB Probe shows whether the selected pixel is black 0 or white 1 both b...

Страница 50: ...n the Diffused Highlight and Shadow fields at the bottom of the Tone and Cast Window Also these points will be marked in your image by sticky densitometers How Auto Range determines Highlight and Shad...

Страница 51: ...ontrol Bar Next select the Pointed cursor from the Control Bar then click on the diamond shaped Highlight white and Shadow black densitometers within the region and move them to the desired locations...

Страница 52: ...sticky densitometer and place it on the Black patch In the Red field next to the Shadow label type 0 The black patch will now become the absolute shadow point Of course setting the input range would b...

Страница 53: ...e the cast setting to None The Highlight point will now keep 100 of its original cast Set the cast setting to Manual and you can now control the Highlight point to any values that you desire This of c...

Страница 54: ...ures The Expert mode gives access to curves for more advanced adjustment of the tonal settings To change the current mode select Preferences from the Edit Menu then choose the desired setting within t...

Страница 55: ...ow fast the transition is between light and dark pixels On a gradation curve this would be the correlation between the quarter tones and three quarter tones Saturation The amount of chromanence presen...

Страница 56: ...ed casts The purpose of the gradation curve is to specify tone compression and contrast Therefore color cor rection should be performed only in the Selective Color window where neutrals and hues are t...

Страница 57: ...radation curve Note Adjustments in the gradation curve change the input to output tonal compression For example moving the three quarter tone point down expands the shadow area of the image by startin...

Страница 58: ...or Selection color wheel to select the individual color to be corrected You can also click on any area of the image and PowerColor automatically detects the selected pixel s high value and whether it...

Страница 59: ...ed color Note Steps 1 and 2 above can be combined by selecting a point in the image which automati cally selects the proper hue and color 3 Adjust the sliders to add or remove color s in a channel Rem...

Страница 60: ...channels together or each channel individually To adjust the limits slide the white slider highlight and or black slider shadow to the desired position The Output Reflectance histogram is a static dis...

Страница 61: ...ed to separations done if Photo is the specified separator in the Preferences window See Chapter 2 3 Using the ColorSync Separator In order to use a ColorSync profile it must be in the ColorSync Profi...

Страница 62: ...ur system in order to use ColorSync profiles Tagging profiles to scanned images The Store ColorSync Profiles in Saved Images check box at the bottom of the ColorSync Window allows the user to tag the...

Страница 63: ...Correcting Images with PowerColor Press CMYK Production Mode 4 4...

Страница 64: ......

Страница 65: ...space Production and Expert The Expert color control mode is discussed in Chapter 5 This chapter explains how to use Production mode and covers the following topics Understanding the CMYK Probe Using...

Страница 66: ......

Страница 67: ...Control P Windows The Probe is a static display of numerical information used as a guide in making color correction changes It is a valuable tool and should always be used in con junction with the sc...

Страница 68: ...y the Magenta plate in the image window press 2 on a Macintosh or Control 2 in Windows The Yellow button shows only the Yellow plate in the image window press 3 on a Macintosh or Control 3 in Windows...

Страница 69: ...ed points in the image which you can use to monitor important tonal ranges as you correct the image To select a point click on the 1 2 or 3 button and click on the desired location in the image The lo...

Страница 70: ...ode are reflected in the individual controls in Expert mode and vice versa To use the Production mode select Production as PowerColor Press Mode in the Preferences window see Setting Preferences in Ch...

Страница 71: ...there is no set workflow that needs to be followed when correcting an image for this manual we will assume a more traditional work flow as follows Set highlight and shadow points Set cast correction s...

Страница 72: ...to the values shown in the Diffused Highlight and Shadow fields within the Productions Control Window Also these points will be marked in your image by sticky densitometers How Auto Range determines H...

Страница 73: ...tings influence how the values react to one another when a new value is typed into one of the fields or when you select a different cast set ting For this example an IT8 target is used although a simi...

Страница 74: ...ts and materials The point is that it is identifiable in the image and we either know were told or have to make an assumption as to how it should reproduce on paper Lets start with knowing that patch...

Страница 75: ...number is gen erally between 260 and 340 GCR UCR Undercolor Removal UCR and Gray Component Replacement GCR replace CMY inks with Black in the neutral areas to reduce total ink on the press GCR UCR is...

Страница 76: ...ction to adjust the CMY colors in the three basic tonal regions To use these tools click on the desired tonal region button left quarter tones middle midtones right three quarter tones and adjust the...

Страница 77: ...on a grayscale step wedge mounted next to the image instead of the image itself To correct casts automatically on neutral grays proceed as follows 1 Click on the gray eyedropper in the Control bar 2 M...

Страница 78: ...lecting Colors to Be Corrected Use the Color Selection color wheel to select the individual color to be corrected You can also click on any area of the image and PowerColor automatically detects the s...

Страница 79: ...the image automati cally selects the proper hue 2 Adjust the sliders in the desired color s to add or remove CMYK inks for that color Remember that small movements in either direction can have sub sta...

Страница 80: ......

Страница 81: ...Correcting Images with PowerColor Press CMYK Expert Mode 5 5...

Страница 82: ......

Страница 83: ...the CMYK Probe see Understanding the CMYK Probe in Chapter 4 Calibrating PowerColor Press CAUTION PowerColor Press should be set up and calibrated only using the procedures in this section Do not make...

Страница 84: ...per thresholds between the saturated and pastel colors The three color Black patch sets the maximum three color density This value is automatically entered into PowerColor s setup table and determines...

Страница 85: ...such as scratches ink spots or fingerprints 3 Mount the print on the bed of your scanner 4 Produce an Overview scan and preview scan a region containing the print For information on producing Overview...

Страница 86: ...ecked and the Point C radial button becomes active 11 Place the box over patch C and click once The Found box for C is checked 12 Click on the Calibrate button The calibration takes less than one seco...

Страница 87: ...ct Gray Balance in the Correction menu The gray balance table shows the corresponding Magenta and Yellow values for Cyan dot percentages in increments of 5 Depending on specific press character istics...

Страница 88: ...target see previous section PowerColor s Save and Recall features are also very useful in the Gray Balance controls allowing you to store and reuse different gray balance tables Editing the Gray Bala...

Страница 89: ...tains a table of values with dot percentages for the Cyan Magenta Yellow and Black inks Setting Dot Gain Presses vary widely in terms of the dot percentages at which they experience maxi mum dot gain...

Страница 90: ...dot percentage indicated under Position Note For greater ease of customization you can enter precise values in any of the fields After entering values in the Position and Gain fields the Dot Gain tabl...

Страница 91: ...tomize and save different tables for different presses This is particularly useful for trade shops that run a variety of presses for different types of work By recalling the desired tables with PowerC...

Страница 92: ...tones midtones three quarter tones and shadows Cast correction is important because PowerColor Press keeps hues and neutrals separate so that color correction can be performed on the hues without affe...

Страница 93: ...of output density The points on the curve called anchor points are from left to right located at the following values highlights quarter tones midtones three quarter tones and shadows By selecting an...

Страница 94: ...nual cast removal you can define the density values or dot percentages for highlight and shadow on the Cyan Magenta and Yellow plates in the appropriate editable field or by selecting the curve you wi...

Страница 95: ...Shadow point will be set to the values shown in the Diffused Highlight and Shadow fields within the Tonal Window Also these points will be marked in your image by sticky densitometers How Auto Range...

Страница 96: ...ou select a different cast set ting For this example an IT8 target is used although a similar target containing a gray wedge would work as well The bottom of the target contains 22 steps of gray borde...

Страница 97: ...w were told or have to make an assumption as to how it should reproduce on paper Lets start with knowing that patch 3 should be neutral and the cyan dot value should be 10 Take the Highlight sticky de...

Страница 98: ...indow see Figure 5 5 To open this window select Gradation in the Correction menu When making gradation corrections in your image always keep the CMYK Probe window open to monitor the changes in numeri...

Страница 99: ...of the colors which make up Grad 3 a term designating the CMY curve However gradation changes affect all colors Above the table is a set of four radio buttons see Figure 5 5 to select the grada tion...

Страница 100: ...the Grad 4 curve represents the total reproduction density of all four inks generally 2 0 for coated stock The area in between Grad 4 and Grad 3 curves represents the skeletal Black By pulling the no...

Страница 101: ...curve in relation to Grad 3 The area between Grad 3 and the UCR GCR curve represents the black gen erated by lowering your total ink To remove or reduce black in certain tonal regions select the appr...

Страница 102: ...the anchor points on the curve are locked into position so you can move each of the points individually without affecting the position of the others Locking the curve also creates additional anchor po...

Страница 103: ...e top of the CMYK Gradation window is a section called Negative Slope Detection This feature is designed to limit the movement of the anchor points for the Grad 3 and Grad 4 curves preventing you from...

Страница 104: ...s a power ful means of controlling the total dot percentage Cyan Dot After UCR GCR shows the maximum Cyan dot percentage after the current UCR GCR curve is applied This column is useful in determining...

Страница 105: ...Determining Black Generation The method of Black generation can be set to UCR or GCR by selecting the desired radial button at the bottom right of the CMYK Gradation window Which method is used is a m...

Страница 106: ......

Страница 107: ...Unsharp Masking and Descreening 6 6...

Страница 108: ......

Страница 109: ...harp masking USM represents a way of adjusting the contrast of edge detail in an image PowerColor s Unsharp Masking window contains extensive tools for fine tuning the sharpness of your images To open...

Страница 110: ...ch of your image s tonal regions The Region Control chart in the Unsharp Masking window shows the five tonal regions in the image from left to right reflecting an overall density range from 0 4 Note T...

Страница 111: ...e or lower the value in this field the active bar is shifted up or down in the chart to reflect the higher or lower starting point for USM Areas below the threshold are smoothed see below areas above...

Страница 112: ...To adjust smoothing in all tonal regions Hold down the Option Shift keys and drag any bar up or down The smoothing bars move together To adjust the threshold of a tonal region Hold down the Control k...

Страница 113: ...in light edge and dark edge areas PowerColor s default is on for both settings Deselecting Light Edges tends to bring out dark edges and detail and vice versa Using the Unsharp Masking Curve The curv...

Страница 114: ...function select Descreen from the Window menu or press D on a Macintosh Control D in Windows Descreening Options The type of descreening to be applied is selected in the top half of the Descreening wi...

Страница 115: ...ndow see above The value entered in this field is reflected in the USM window Final Scans Only applies descreening only to the final image to be scanned but not to any prescans Scale USM limits the de...

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Страница 117: ...Scanning Images to Disk 7 7...

Страница 118: ......

Страница 119: ...ure you have made all necessary adjustments Note To review the parameters for each region individually make sure each desired region is selected in the Queue Manager as indicated by the red frame arou...

Страница 120: ...options are RGB standard Red Green and Blue Note If you scan in CMYK color space with Photo RGB selected in Preferences as the sepa rator the final image will not represent accurate color To scan in t...

Страница 121: ...reen or Blue color channel respectively Note Whenever the CMYK scan mode is select ed PowerColor automatically switches to the CMYK mode if Press is the designated separa tor in Preferences and replac...

Страница 122: ...e small lock icon next to the Line Screen field locks the scanner s resolution at the next highest native resolution When locked the scanner s native resolution is used when unlocked the final scan ou...

Страница 123: ...rently before performing the final scan proceed as follows 1 Select the region in the Queue Manager by double clicking on it 2 Select Save from the File menu or press S on a Macintosh 3 In the standar...

Страница 124: ...tch Scanning All Images PowerColor s Queue Manager allows you to send all regions to be final scanned in one batch To do so click on the Scan All button Note Regions are scanned in the order they appe...

Страница 125: ...Tips and Tricks 8 8...

Страница 126: ......

Страница 127: ...n To resize a region change the Preview Size in the Preferences window This setting defines the dimensions of the image window in pixels Resizing the image window itself does not change the region s d...

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