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Correcting image distortion and noise, About lens distortion

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PHOTOSHOP CS3 205 User Guide Correcting image distortion and noise About lens distortion Barrel distortion is a lens defect that causes straight lines to bow out toward the edges of the image. Pincushion distortion is the opposite effect, where straight lines bend inward. Examples of barrel distortion (left) and pincushion distortion (right) Vignetting is a defect where the edges, especially the corners, of an image are darker than the center. Chromatic aberration appears as a color fringe along the edges of objects caused by the lens focusing on different colors of light in different planes. Some lenses exhibit these defects depending on the focal length or the f-stop used. You can set the Lens Correction filter to use settings based on the camera, lens, and focal length used to make the image. Correct lens distortion and adjust perspective The Lens Correction filter fixes common lens flaws such as barrel and pincushion distortion, vignetting, and chromatic aberration. The filter works with 8-bits and 16-bits-per-channel images only. You can also use the filter to rotate an image or fix image perspective caused by vertical or horizontal camera tilt. The filter's image grid makes these adjustments easier and more accurate than using the Transform command. Correct image perspective and lens flaws 1 Choose Filter > Distort > Lens Correction. 2 Set the grid and image zoom. As you work you may want to adjust the grid lines to help you judge the amount of correction to make. See Adjust the Lens Correction preview and grid, below. 3 (Optional) Choose a preset list of settings from the Settings menu. Lens Default uses settings that you previously saved for the camera, lens, focal length, and f-stop combination used to make the image. Previous Conversion uses the settings used in your last lens correction. Any group of custom settings you saved are listed at the bottom of the menu. See Set camera and lens defaults, below. 4 Set any of the following options to correct your image. Remove Distortion Corrects lens barrel or pincushion distortion. Move the slider to straighten horizontal and vertical lines that bend either away from or toward the center of the image. You can also use the Remove Distortion tool to make this correction. Drag toward the center of the image to correct for barrel distortion and toward the edge of the image to correct for pincushion distortion. Adjust the Edge option to specify how you want to handle any resulting blank image edges.

Section	Page
Contents	3
Chapter 1: Getting started	8
Installation	8
Requirements	8
Install the software	8
Activate the software	8
Register	8
Read Me	9
Adobe Help	9
Adobe Help resources	9
Using Help in the product	10
Resources	12
Adobe Video Workshop	12
Photoshop CS3 videos	13
Extras	14
Bridge Home	15
Adobe Design Center	16
Adobe Developer Center	17
Customer support	17
Downloads	17
Adobe Labs	18
User communities	18
What’s new?	18
Productivity enhancements	18
Image editing improvements	19
Compositing enhancements	19
3D and motion advances	20
Comprehensive image analysis	20
Chapter 2: Workspace	21
Workspace basics	21
Workspace overview	21
Customize the workspace	23
Save, delete, and switch between workspaces	27
Display or hide tool tips	28
Adobe Bridge	28
Palettes and menus	28
Enter values in palettes, dialog boxes, and the options bar	28
About pop-up sliders	29
About scrubby sliders	29
Working with pop-up palettes	29
Display context menus	31
Define a set of menus	31
Delete a set of menus	32
Temporarily show hidden menu items	32
Turn menu colors on or off	32
Tools	32
About tools	32
Selection tools gallery	34
Crop and slice tools gallery	34
Retouching tools gallery	34
Painting tools gallery	35
Drawing and type tools gallery	36
Annotation, measuring, and navigation tools gallery	36
Use a tool	37
Cycle through hidden tools	37
Change tool pointers	37
Using the options bar	38
Create and use tool presets	38
Viewing images	40
Change the screen mode	40
View another area of an image	40
Use the Navigator palette	41
Zoom in or out	41
View images in multiple windows	43
Match locations in images	43
Match zoom and locations in images	43
Work with the Info palette	44
Display file information in the document window	46
Duplicate an image	48
Rulers, the grid, and guides	48
About rulers	48
Change a ruler’s zero origin	48
Change the unit of measurement	49
Specify columns for an image	49
Position with the Ruler tool	49
Position with guides and the grid	50
Use snapping	52
Show or hide Extras	52
Work with the Preset Manager	53
About the Preset Manager	53
Load a library of preset items	54
Manage preset items	54
Preferences	55
About preferences	55
Open a preferences dialog box	56
Restore all preferences to default settings	56
Disable and enable warning messages	56
Specify a legacy serial number	56
Plug-ins	57
About plug-in modules	57
Install a plug-in module	57
Select an additional plug-ins folder	57
Suppress the loading of plug-ins	57
View information about installed plug-ins	57
Recovery and undo	58
Use the Undo or Redo commands	58
Revert to the last saved version	58
Restore part of an image to its previously saved version	58
Cancel an operation	58
Receive notification when an operation is completed	58
Work with the History palette	59
Make a snapshot of an image	62
Memory and performance	63
Allocate RAM to Photoshop	63
Assigning scratch disks	63
Change the scratch disk assignment	64
Enable 3D Acceleration (Adobe® Photoshop® CS3 Extended)	64
Specify history and cache settings	64
Free memory	64
Chapter 3: Opening and importing images	65
Photoshop images	65
About bitmap images	65
About vector graphics	65
Combining vector graphics and bitmap images	66
Color channels	66
Bit depth	67
Convert between bit depths	67
Image size and resolution	68
About pixel dimensions and resolution	68
File size	69
About monitor resolution	70
About printer resolution	70
Resampling	71
Change pixel dimensions of an image	72
Change the print dimensions and resolution	73
Determine a suggested resolution for an image	73
View the print size on-screen	74
Acquiring images from cameras and scanners	74
Acquiring digital images from cameras	74
Import images from a digital camera using WIA (Windows only)	74
Importing scanned images	75
Creating, opening, and importing images	76
Create a new image	76
Adobe Version Cue	77
Open files	77
Open PDF files	78
Open an EPS file	80
Open a Photo CD file	80
Import PICT files and resources (Mac OS)	81
Placing files	81
About placing files	81
Place a file in Photoshop	82
Place PDF or Illustrator files in Photoshop	83
Paste Adobe Illustrator art into Photoshop	83
High dynamic range images	84
About high dynamic range images	84
Merge images to HDR	86
Adjust dynamic range view for HDR images	88
Convert from 32 bits to 8 or 16 bpc	88
About the HDR Color Picker (Photoshop Extended)	90
Paint on HDR images (Photoshop Extended)	91
Chapter 4: Camera Raw	92
Introduction to Camera Raw	92
About camera raw files	92
About Camera Raw	92
About the Digital Negative (DNG) format	93
Processing images with Camera Raw	94
Camera Raw dialog box overview	96
Work with the Camera Raw cache in Bridge	97
Navigating, opening, and saving images	97
Process, compare, and rate multiple images in Camera Raw	97
Automating image processing with Camera Raw	98
Open images in Camera Raw	99
Save a camera raw image in another format	99
Making color and tonal adjustments in Camera Raw	100
Using histogram and RGB levels in Camera Raw	100
Preview highlight and shadow clipping in Camera Raw	101
White balance controls in Camera Raw	101
Adjust tone in Camera Raw	103
Fine-tune tone curves in Camera Raw	104
Clarity, Saturation, and Vibrance controls in Camera Raw	105
HSL / Grayscale controls in Camera Raw	105
Tone a grayscale image in Camera Raw	105
Adjust color rendering for your camera in Camera Raw	105
Compensate for chromatic aberration in Camera Raw	106
Compensate for lens vignetting in Camera Raw	107
Modifying images with Camera Raw	107
Rotate images with Camera Raw	107
Straighten images in Camera Raw	107
Crop selected images in Camera Raw	108
Remove red-eye in Camera Raw	108
Retouch images in Camera Raw	108
Adjust sharpening in Camera Raw	109
Reducing noise in Camera Raw	109
Camera Raw settings	110
Save, reset, and load Camera Raw settings	110
Specify where Camera Raw settings are stored	111
Copy and paste Camera Raw settings	111
Apply saved Camera Raw settings	112
Export Camera Raw settings and DNG previews	112
Camera Raw Workflow options	113
Chapter 5: Color	114
About color	114
Understanding color	114
Color models, spaces, and modes	115
Adjusting color hue, saturation, and brightness	116
Color modes	117
RGB Color mode	117
CMYK Color mode	117
Lab Color mode	118
Grayscale mode	118
Bitmap mode	118
Duotone mode	118
Indexed Color mode	118
Multichannel mode	119
Converting between color modes	119
Convert an image to another color mode	119
Add a conditional mode change to an action	120
Convert a color photo to Grayscale mode	120
Convert an image to Bitmap mode	120
Convert a Bitmap mode image to Grayscale mode	122
Convert a grayscale or RGB image to indexed color	122
Customize indexed color tables	124
Choosing colors	125
About foreground and background colors	125
Choose colors in the toolbox	125
Choose colors with the Eyedropper tool	126
Adobe Color Picker overview	126
Choose a color with the Adobe Color Picker	127
Choose web-safe colors	129
Choose a CMYK equivalent for a non-printable color	129
Choose a spot color	130
Change the color picker	131
Color palette overview	131
Select a color in the Color palette	132
Select a color in the Swatches palette	132
Add, replace, and delete color swatches	132
Manage swatch libraries	133
Share swatches between applications	134
Chapter 6: Color management	135
Understanding color management	135
Why colors sometimes don’t match	135
What is a color management system?	135
Do you need color management?	136
Creating a viewing environment for color management	137
Keeping colors consistent	137
About color management in Adobe applications	137
Basic steps for producing consistent color	138
Synchronize color settings across Adobe applications	139
Set up color management	139
Change the appearance of CMYK black (Illustrator, InDesign)	140
Managing process and spot colors	140
Color-managing imported images	141
Color-managing imported images (Illustrator, InDesign)	141
Using a safe CMYK workflow	141
Preparing imported graphics for color management	142
View or change profiles for imported bitmap images (InDesign)	142
Color-managing documents for online viewing	143
Color-managing documents for online viewing	143
Color-managing PDFs for online viewing	143
Color-managing HTML documents for online viewing	143
Proofing colors	144
Soft-proofing colors	144
Soft-proof colors	144
Save or load a custom proof setup	145
Soft-proof colors (Acrobat)	145
Color-managing documents when printing	146
Printing with color management	146
Letting the printer determine colors when printing	146
Letting the application determine colors when printing	146
Obtaining custom profiles for desktop printers	146
Color-managing PDFs for printing	147
Working with color profiles	148
About color profiles	148
About monitor calibration and characterization	149
Calibrate and profile your monitor	150
Install a color profile	150
Embed a color profile	150
Embed a color profile (Acrobat)	151
Changing the color profile for a document	151
Assign or remove a color profile (Illustrator, Photoshop)	151
Assign or remove a color profile (InDesign)	151
Convert document colors to another profile (Photoshop)	152
Convert document colors to another profile	152
Color settings	153
Customize color settings	153
About color working spaces	153
Working space options	153
About missing and mismatched color profiles	154
Color management policy options	155
Color conversion options	156
About rendering intents	156
Advanced controls in Photoshop	157
Chapter 7: Making color and tonal adjustments	158
Viewing histograms and pixel values	158
About histograms	158
Histogram palette overview	158
View the histogram for a multilayered document	161
Preview histogram adjustments	161
Refresh the histogram display	161
View color values in an image	162
Adjusting color samplers	163
Understanding color adjustments	163
Before making color and tonal adjustments	163
Correcting images	164
Color adjustment commands	165
Make a color adjustment	165
Save and reapply adjustment dialog box settings	166
Correcting Colors in CMYK and RGB	166
Identify out-of-gamut colors	166
Adjusting image color and tone	167
Levels overview	167
Adjust tonal range using Levels	168
Adjust color using Levels	169
Curves overview	170
Adjust color and tonality with Curves	171
Color correct using the eyedroppers	174
Adjust hue and saturation	175
Convert a color image to black and white	177
Improve shadow and highlight detail	178
Add contrast to a photo	179
Adjust Exposure for HDR images	180
Targeting images for press	181
Setting highlight and shadow target values	181
Using Levels to preserve highlight and shadow details for printing	181
To set target values using the eyedroppers	181
Matching, replacing, and mixing colors	183
Match the color in different images	183
Replace the color of objects in an image	185
Mix color channels	186
Make selective color adjustments	188
Making quick image adjustments	189
Change the color balance using the Photo Filter command	189
Apply the Color Balance command	189
Apply the Brightness/Contrast command	190
Apply the Auto Levels command	190
Apply the Auto Contrast command	191
Remove a color cast with Auto Color	192
Set Auto adjustment options	192
Apply the Variations command	193
To use the Equalize command	194
Applying special color effects to images	194
Desaturate colors	194
Invert colors	195
Create a two-value black and white image	195
Posterize an image	195
Apply a gradient map to an image	196
Chapter 8: Retouching and transforming	197
Adjusting crop, rotation, and canvas	197
Crop images	197
Transform perspective while cropping	199
Crop and Straighten photos	200
Rotate or flip an entire image	200
Change the canvas size	201
Make a photo frame	202
Retouching and repairing images	202
About the Clone Source palette	202
Retouch with the Clone Stamp tool	202
Set sample sources for cloning and healing	203
Retouch with the Healing Brush tool	205
Retouch with the Spot Healing Brush tool	206
Patch an area	207
Remove red eye	209
Replace color in image areas	209
Smudge image areas	210
Blur image areas	210
Sharpen image areas	210
Dodge or burn areas	211
Adjust color saturation in image areas	211
Correcting image distortion and noise	212
About lens distortion	212
Correct lens distortion and adjust perspective	212
Reduce image noise and JPEG artifacts	214
Adjusting image sharpness and blur	214
Sharpen images	214
Sharpen using Smart Sharpen	215
Sharpen using Unsharp Mask	216
Sharpen selectively	217
Add lens blur	219
Transforming objects	220
Apply transformations	220
Select an item to transform	221
Set or move the reference point for a transformation	221
Scale, rotate, skew, distort, apply perspective, or warp	221
Flip or rotate precisely	222
Repeat a transformation	223
Duplicate an item when transforming it	223
Transform freely	223
Warp an item	224
Liquify filter	226
Liquify filter overview	226
Distortion tools	227
Distort an image	228
Freeze and thaw areas	228
Reconstruct distortions	229
Work with meshes	231
Work with backdrops	231
Vanishing Point	232
About Vanishing Point	232
Vanishing Point dialog box overview	232
Work in Vanishing Point	234
About perspective planes and the grid	236
Define and adjust perspective planes in Vanishing Point	236
About selections in Vanishing Point	238
Fill selections with another area of an image	240
Copy selections in Vanishing Point	241
Paste an item into Vanishing Point	242
Paint with a color in Vanishing Point	242
Paint with sampled pixels in Vanishing Point	243
Measure in Vanishing Point	244
Export measurements, textures, and 3D information	245
Render grids to Photoshop	246
Create panoramic images	246
About Photomerge	246
Take pictures for use with Photomerge	246
Create a Photomerge composition	247
Create a photomerge interactively	248
Chapter 9: Selecting	251
Making selections	251
About selecting pixels	251
Select, deselect, and reselect pixels	251
Select with the marquee tools	252
Select with the Lasso tool	253
Select with the Polygonal Lasso tool	253
Select with the Magnetic Lasso tool	254
Select with the Quick Selection tool	256
Select with the Magic Wand tool	257
Select a color range	257
Adjusting pixel selections	259
Move, hide, or invert a selection	259
Adjust selections manually	260
Expand or contract a selection by a specific number of pixels	261
Create a selection around a selection border	261
Expand a selection to include areas with similar color	262
Clean up stray pixels in a color-based selection	262
Refine selection edges	262
Soften the edges of selections	263
Remove fringe pixels from a selection	264
Moving and copying selected pixels	265
Move a selection	265
Copy selections	265
Copy between applications	267
Deleting and extracting objects	269
Remove (cut) an object from a photo	269
Delete selected pixels	269
Extract an object from its background	269
Channels	271
About channels	271
Channels palette overview	272
Show or hide a channel	273
Show color channels in color	273
Select and edit channels	273
Rearrange and rename alpha and spot channels	274
Duplicate channels	274
Split channels into separate images	275
Merge channels	275
Delete a channel	276
Saving selections and using masks	276
About masks and alpha channels	276
Create a temporary quick mask	277
Change Quick Mask options	278
Create and edit alpha channel masks	279
Save and load selections	280
Channel calculations	282
Blending layers and channels	282
Blend channels with the Apply Image command	282
Blend channels with the Calculations command	283
Add and Subtract blending modes	283
Chapter 10: Layers	285
Layer Basics	285
About layers	285
Layers palette overview	286
Convert background and layers	287
Create layers and groups	287
Duplicate layers	288
Show or hide a layer, group, or style	289
View layers and groups within a group	289
Sample from all visible layers	289
Change transparency preferences	289
Selecting, grouping, and linking layers	290
Select layers	290
Group and ungroup layers	291
Add layers to a group	291
Link and unlink layers	291
Moving, stacking, and locking layers	291
Change the stack order of layers and groups	291
Show layer edges and handles	292
Move the content of layers	292
Align objects on different layers	293
Distribute layers and groups evenly	293
Automatically align image layers	294
Auto blend layers	295
Rotate a layer	295
Lock layers	296
Managing layers	296
Rename a layer or group	296
Assign a color to a layer or group	297
Rasterize layers	297
Delete a layer or group	297
Export layers	298
Track file size	298
Merge and stamp layers	298
Setting opacity and blending	299
Specify opacity for a layer or group	299
Specify fill opacity for a layer	300
Specify a blending mode for a layer or group	300
Filling new layers with a neutral color	300
Create a knockout	301
Exclude channels from blending	302
Group blend effects	302

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PHOTOSHOP CS3

User Guide

205

Correcting image distortion and noise

About lens distortion

Barrel distortion

is a lens defect that causes straight lines to bow out toward the edges of the image.

Pincushion

distortion

is the opposite effect, where straight lines bend inward.

Examples of barrel distortion (left) and pincushion distortion (right)

Vignetting

is a defect where the edges, especially the corners, of an image are darker than the center.

Chromatic

aberration

appears as a color fringe along the edges of objects caused by the lens focusing on different colors of light

in different planes.

Some lenses exhibit these defects depending on the focal length or the f-stop used. You can set the Lens Correction

filter to use settings based on the camera, lens, and focal length used to make the image.

Correct lens distortion and adjust perspective

The Lens Correction filter fixes common lens flaws such as barrel and pincushion distortion, vignetting, and

chromatic aberration. The filter works with 8-bits and 16-bits-per-channel images only.

You can also use the filter to rotate an image or fix image perspective caused by vertical or horizontal camera tilt. The

filter’s image grid makes these adjustments easier and more accurate than using the Transform command.

Correct image perspective and lens flaws

Choose Filter > Distort > Lens Correction.

Set the grid and image zoom. As you work you may want to adjust the grid lines to help you judge the amount of

correction to make. See Adjust the Lens Correction preview and grid, below.

(Optional) Choose a preset list of settings from the Settings menu. Lens Default uses settings that you previously

saved for the camera, lens, focal length, and f-stop combination used to make the image. Previous Conversion uses

the settings used in your last lens correction. Any group of custom settings you saved are listed at the bottom of the

menu. See Set camera and lens defaults, below.

Set any of the following options to correct your image.

Remove Distortion

Corrects lens barrel or pincushion distortion. Move the slider to straighten horizontal and

vertical lines that bend either away from or toward the center of the image. You can also use the Remove Distortion

tool

to make this correction. Drag toward the center of the image to correct for barrel distortion and toward the

edge of the image to correct for pincushion distortion. Adjust the Edge option to specify how you want to handle any

resulting blank image edges.