Digital Imaging Study

What We See  Visible Electromagnetic Spectrum: – 400 nanometers (approximate blue) – 700 nanometers (approximate red)  Levels of Brightness - 256 – Human eye can only distinguish a portion – Inkjet or Laser can only print a portion  Gray Levels - 256 – Human eye can only distinguish 20 to 30 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 4

Color  Requirements – Object – Light Source – Observer  Color Gradations – Hue - color as described by wave length – Saturation - amount of color present – Lightness  Amount of light  Distinction between dark and light  Color Types – Additive - light emitting (RGB) – Subtractive - light reflecting (CMY) 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 5

Perspective  Depth Perception comes from: – Human Stereoscopy – Relative Size – Precedence – Perspective – Atmospheric Haze – Other Clues  Viewing Geometry – Spatial Area or Distance – Angles – Time 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 6

Image Acquisition  Continuous Tone Subject - Selected subject material for black & whites or color  Sampling (continuous tone color or gray scale) – Digital Camera or Scanner – Collect analog samples in a Sampling Grid (pixel count, ie. 640 x 480)  Quantization & Conversion (Rasterization) – Spatial Aspect describing grid location – Tonal Aspect describing color (Trichromacy considerations)  Output Frequencies – Pixel Grid – Spot Addressability Grid – Screener Dot Grid 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 8

Basic Image Processing  Improve  Correct  Restore  Analyze  Change  Archive  Retrieve  Synthesize  Preparation (color, composition, & effects)  Presentation or Viewing 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 9

Image Analysis  Fundamental Processes – Counting – Measuring – Matching – Classifying  Segmentation  Feature Extraction  Outlining (Skeletonization)  Object Classification 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 10

CSI: Crime Scene Investigation  Video Monitor Recording Analysis – Restoration – Enhancement – Isolation & Extraction  Finger Print Matching  Facial or Body Matching  Feature Recognition  Location Triangulation  Spatial Placement & Measurement  Document Analysis  Ballistics & Trajectory Analysis 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 11

Image Analysis with ImageJ Basic Operations – Selection Tools: Select an image area (4 types of marques) – Line Tools: Draw a line on an image (3 types of lines) – Crosshairs: Mark image locations with coordinates & brightness – Wand Tool: Automatically find the edge of an object – Text Tool: Add text or labels to an image – Magnifying Glass: Increase & decrease image size – Scrolling Tool: Move image if larger than window – Color Picker: Set the drawing colors 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 12

ImageJ Processing  Undo  Revert  Cropping  Clear Outside (make a perimeter to clear extraneous objects around a subject area)  Enhance Brightness/Contrast  Remove Noise  Rotate Image  Convert to Grayscale (8 bit 256 shades)  Thresholding (binary contrast enhancement)  Counting & Measuring – Setting the measurement scale – Measuring distance between points – Measuring Area – Counting particles 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 13

Seeing It In Print  Traditional Printing is Binary – Lay down ink – Don’t lay down ink  Halftone Solution – Dots smaller than eye resolution (150 lpi) – Illusion of continuous tone  Gray Levels 256 (16x16 spot grid) – (addressability (spi)/screen ruling (lpi))2 + 1 – Needed gray levels - 16 + 4% noise for vignette  Halftone Methods - assigning halftone dots – AM Screening - Spatial address is constant, dot size is modulated – FM Screening - Dot size is constant, spatial addressing is modulated  the higher the micron size, the coarser (more granular) the print 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 14

Screen Ruling  Commercial printing (GRACol) – General Requirements for Applications in Commercial Offset Lithography – 175 lpi  Standard publication printing (SWOP) – Specification for Web Offset Publishing – 133 lpi or 150 lpi (SWOPv2)  Newspaper printing (SNAP) – Specifications for Non-Heatset Advertising Printing – 85 to 100 lpi 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 15

Printing Color  Print is reflective (subtractive) - CMYK  separations represent color channels  Each separation has its own screen  AM screens are spatially offset (w/in90°) – Yellow = 0° screen angle with Black = 45° angle – Cyan = 15° screen angle with Magenta = 75° angle  FM is random and eliminates angular screening – Many AM problems are overcome:  Loss of detail minimized  Subject and screening moiré is eliminated  Rosette structures are eliminated  Gradient blends tend to print smoother 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 16

Image Storage  Storage Systems – DAMS & CMS – Desktop Systems  Adobe Bridge  NikonView  Storage Media – CD (r & rw) – DVD – Magnetic (disk or other media)  Search & Retrieval Logic – Boolean Logic – Fuzzy logic 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 17

Search & Retrieval Mechanisms  Key Words  Measurement  Search Fields Parameters  Latitude & Longitude  Particular Characteristics  Slide Coordinates  Time & Date  Color Recognition  Size or Density  Matching Shapes  Thumbnails  Numeric Values  “Wild Cards”  Query By Image  Cross Correlation Context (QBIC) 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 18

Image Compression  Compression Reasons – Transport – Storage  Standard Compression Schemes – Lossless: preserves exact image data content (ratios up to 3:1) – Lossy: preserves arbitrary levels of image quality (ratios up to 100:1)  Operational Symetry – Compression  Symmetrical: compression & decompression take similar time  Asymmetrical: compression takes more time then decompression – Decompression  Asymmetrical: decompression takes more time than compression  Information Loss – Compression  Detail is lost in high frequency low contrast areas where the eye is not sensitive – Down Sampling  Information is lost throughout overall image resolution independent of contrast 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 19

Compression Types  Lossless (Transmissions & Facsimile) – CCITT Group 3 & 4 - International Telephone & Telegraph Consultative Committee – JBIG - Joint Bi-level Image Experts Group  Lossy – JPEG - Joint Photographic Experts Group  Fine (1:4)  Normal (1:8)  Basic (1:16) – MPEG - Moving Picture Experts Group  MPEG-1: low resolution image sequences (320x240 pixels)  MPEG-2: higher resolution applications (640x480 pixels) 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 20

Photo Compression & Storage Relative JPEG storage on 16 MB media Image Size Pixel Size Fine (1:4) Normal (1:8) Basic (1:16) Full 2560 x 1920 6 12 25 UXGA 1600 x 1200 16 31 59 SXGA 1280 x 960 24 47 86 XGA 1024 x 768 37 69 121 VGA 640 x 480 86 144 229 3:2 2560 x 1704 7 14 27 Courtesy of Nikon: The Nikon Guide to Digital Photography with the CoolPix 5700 Digital Camera 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 21

Image Quality  Image Resolution: – Spatial Density & Frequency (high & low) – Brightness, Contrast, Color – Optics - system capability to resolve details  Dependencies: – Number of Pixels (pixels/inch) – Number of Lines (lines/inch) – Range of Brightness Values (dynamic range - gray levels)  Radiant intensity - reflected light  Luminous brightness - acquired light – Color & Contrast – Viewing Geometry  Image dimensions  Viewing distance  Aspect ratio (rectangularity) – Compression Ratios & Relative Results 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 23

Quality Deficiencies  Detail Resolution  Image contrast & white balance  Color Quality  Tonal Quality & Range  Composition  Spatial Characteristics  Annoying Image Noise  Out-of-focus (specific objects or overall)  Motion blur (specific objects or overall)  Image Geometry  Lost Information from Compression 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 24

Causes of Image Defects  Limitations of Optics – Built-in Limitations – Dirt, Particles, Smudges  Imperfect Detectors  Inadequate Illumination  Non-uniform Illumination  Too Much Illumination  An Undesirable Viewpoint (perspective)  Unplanned Movement – The Subject – The Capture Device – Capture Device Settings (Aperture & Shutter Speed) 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 25

Noise  Definition - random extraneous pixels that are not part of the image detail  Causes – High ISO setting – Under exposure – Shooting in darkness with long shutter speed  Types – Luminance Noise: gray scale data, grainy, patchy – Color Noise: colored artifacts – Compression artifacts – Film grain patterns from scanning – Scanner or camera sensor generated noise 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 26

Image Distortion  Barrel Distortion - lens defect causing lines to bow out  Pincushion Distortion - lens defect causing line to bow in  Vignetting - image edges and corners darker than center  Chromatic Aberration - color fringes along edges of image objects 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 27

Correction Strategies  Better to optimize or correct the acquisition process – Not always practical, feasible, achievable – Not always possible  Correct after image is digitized & stored – Corrections may not deliver the highest quality result – Corrections depend on planned purpose (desirability vs. usability) 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 29

Approaches  Processing Viewpoint: – Subjective - repetition until satisfactory – Objective - measured and applied once  Processing Types: – Contrast enhancement or degradation – Spatial enhancement or degradation 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 30

The Correction Setup  Lighting (approximately 65K)  Digital Camera (settings if appropriate)  Calibration (monitor, scanner, printer)  Standard profiles (hardware & software)  Image profiles and metadata  Image analysis & correction plan  Conversion - convert images to TIFF 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 31

Correction Steps (per Adobe)  Duplicate the original image or scan  Check image quality & confirm resolution is appropriate for use  Crop image to final size & orientation  Repair flaws in scan of damaged photos  Adjust overall contrast or tonal range  Adjust white balance to modify original photo conditions  Remove any color casts  Adjust color & tone is specific parts to bring out highlights, midtones, shadows, and desaturated colors  Sharpen the over-all focus of the image 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 32

Correction Techniques  Contrast Expansion & Manipulation  Neighborhood Averaging  Gaussian Smoothing (to reduce noise)  Median Filter Application (reduce shot noise)  Conditional Smoothing  Manipulation of Pixel Patterns in an area by addition, subtraction, or averaging  Segmentation (critical in creating information) – Dividing an image into regions corresponding to structural units in the scene – Distinguishing objects of interest  Halftone Removal  Removal of Motion Blur based on vector of direction and exposure time 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 33

Enhancement & Restoration  Histogram Equalization & Filters  Image Morphology – Contrast Enhancement – Edge Enhancement & Skeletonization – Image Erosion - shrinking or removing selected objects – Image Dilation - expansion of selected objects  Geometric Transformation – Rotation – Scaling – Warping  Interpolation  Segmentation (removing distracting or useless information - ie. Background subtraction) 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 34

Specific Processes  Complement Image - negative  Histogram Sliding - brighten or darken image  Binary Contrast Enhancement - create high contrast  Brightness Slicing - create high contrast of an object  Image Subtraction - remove common background info  Image Division - spectral ratioing  Image Addition - average identical scenes to reduce noise  Low-pass Filter - attenuate image noise from high freq.  Unsharp Masking - sharpen by subtracting a brightness-scaled image from the original  High-pass Filter - highlights high frequency details  Sobel Edge Enhancement - produce object edges  Shift & Difference Edge Enhancement - vertical, horizontal, and diagonal edges 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 35

Specific Processes (continued)  Prewitt Gradient Edge Enhancement - produce object edges in an image  Laplacian Edge Enhancement - extracts all edges in an image  Line Segment Enhancement - produce edge-enhanced images  Median & Ranking Filters - remove impulse noise spikes  Fourier Frequency Transform Filtering - selective removal of periodic noise patterns  Translation Transformation - horizontal or vertical geometric adjustments  Rotation Transformation - geometric rotation of an image  Scaling Transformation - geometric adjustment of size  Warping Transformation - correct geometric distortions created in image acquisition 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 36

Key Photoshop Tools  Dodge Tool - lighten highlights, reduce light  Sponge Tool - saturate a color by adjusting purity  Clone Stamp Tool - uses pixels in one area to replace pixels in another area  Spot Healing Brush - paints with sampled pixels from around retouch area  Healing Brush Tool - apply & blend pixels from one area to another  Patch Tool - combines area capture with blending properties 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 38

Key Photoshop Filters  Unsharpen Mask Filter - adjust edge contrast giving illusion of better focus  Reduce Noise Filter - eliminate noise  Sharpen Filter - reduce lens blur  Vanishing Point Filter - correct perspective  Lens Correction Filter - address distortion issues 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 39

References  Adobe. (2005). Adobe Photoshop CS2 classroom in a book. Berkeley, CA: Peachpit Press.  Baxes, Gregory A. (1994). Digital image processing principles and applications. New York: John Wiley & Sons, Inc.  Haynes, Barry & Crumpler, Wendy. (2002). Photoshop 7 artistry. Indianapolis, IN: New Riders Publishing.  London, Sherry & Grossman, Rhoda. (2002). Photoshop 7 magic. Indianapolis, IN: New Riders Publishing.  McClelland, Deke. (2005). Adobe Photoshop CS2 one-on-one. Sebastopol, CA: O’Reilly Media, Inc.  Rasband, W.S. (2006). ImageJ. Bethesda, MD: U.S. National Institute of Health. Retrieved October 25, 2006, from http://rsb.info.nih.gov/ij  Russ, John C. (2002). The image processing handbook, fourth edition. Boca Raton, FL: CRC Press LLC.  Sigg, Franz. (2005). Resolution and contrast for image reproduction. Slide Presentation. Rochester, NY: RIT. 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 40

Image Gallery - Settings  Photoshop Color Settings – RGB: Adobe RGB (1998) – CMYK: U.S. Web Coated (SWOP) v2 – Gray & Spot Colors: 20% Dot Gain – Embedded Profiles: Preserve – Rendering Intent: Relative Colorimetric – Color Engine: Adobe (ACE) – Black Point Compensation & Dither  File Save – TIFF with LZW (Lossless) Compression – Interleaved – Macintosh  Acrobat – Default settings for High Quality Desktop Printing 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 42

Image Gallery - Procedure  Load Image into Photoshop  Convert Profile (sRGB to Adobe RGB)  Apply Process(es) or Filter(s)  Resize Image  Save As… in Processed Image Folder 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 43

Auto Corrected Original Photograph Photograph across Levels Auto Corrected Photograph with Flash Photograph for Color Manually Corrected Auto Corrected Photograph using Photograph for Contrast Color Balance for Shadows, Mid-tones, and Highlights Manually Corrected Photograph using Contrast & Brightness Yellow Flower Collection 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 44

Brightness & Contrast Brightness = 100 and Contrast = 100 Photograph manually adjusted for produces Neutral Gray brightness and contrast by holding one setting at 0 while adjusting the other setting Original Photograph Brightness = 0 and Contrast = -100 produces Black Brightness = -100 Brightness = 49 Brightness = 0 Contrast = 0 Contrast = 0 Contrast = 49 Brightness = -49 Brightness = 100 Brightness = 0 Brightness = 0 Contrast = 0 Contrast = 0 Contrast = -49 Contrast = 100 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 45

Color Balance Photograph manually adjusted for Shadows, Mid-tones, and Highlights to increase the Greens and strengthen the yellows Original Photograph Photograph after Slight Adjustments 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 46

Purple Flower Collection Application of Image-Wide Adjustments to Original Photograph Tone and Color Tone & Color Inverted Tone & Color Equalized Tone & Color Thresholded Tone & Color Posterized 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 47

Patio Stones - Sharpening The original photograph was taken out of focus This correction is by applying Smart This correction was made by applying Sharpening: Correction Angle 90° the Unsharp Mask: Amount 90% Radius 40 Pixels Radius 16.6 Pixels Motion Blur Correction Threshold 48 Levels 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 48

Bringing Out Details with Shadows & Highlights The object is to bring more detail to Tyler (the dog). #1. The original photograph #2. The desaturated photograph #3. Adjusted highlights and shadows: Shadows set to 100% #1 Highlights set to 0% #2 #3 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 49

Bringing Out Details with Gradient Mapping Tyler is not visible in the original photograph (upper left), but he becomes obvious in the two gradient- mapped versions below (see the circled areas). I had no idea he was in the picture until it was mapped. It was a complete surprise. 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 50

Bringing Out Details with Contour and Edge Filters While Tyler is not visible in the original photograph (previous slide), and somewhat visible with Gradient Mapping, he is easily located in these two filtered images. The upper image was created with the Find Edges Filter. The lower image was created with the Contour Filter where the Levels were set to 8 to eliminate detail 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 51

Adjustments with Photo Cool and Warm Filters The original photograph with some posterization tendency in the upper left darker blue sky A Cool 80 filter applied to photograph A Warm 85 filter mitigates the still leaves a small amount of posterization tendency and softens posterization tendency in the upper the colors overall left darker blue sky 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 53

Adjustments with Photo Colored Filters Application of filters (in this case) demonstrates viewer perception and subjectivity The original photograph with some detail lost in the shadows and some sharpness overall A blue filter applied to photograph still A yellow filter warms the photograph, softens the photo but is a little cool bringing out some green and a little more detail 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 54

Original Photograph Cyan Proof Plate Magenta Proof Plate Yellow Proof Plate Plate Proof Separations Black Proof Plate CMY Proof CMYK Proof 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 55

JPEG Compression The original photograph was compressed during File Save As… 1. Original TIFF Image 1. 2. JPEG - Maximum 3. JPEG - High 4. JPEG - Medium 5. JPEG - Low 2. 3. 4. 5. 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 56

Separated Red Separated Green Separated Blue ImageJ RGB Separation The original photograph was separated using the ImageJ image separation procedure. This produced three images that were remerged using a reciprocal procedure to generate the fourth image. Merged RGB Original Photograph 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 57

ImageJ Christmas Collection - Procedures & Filters Three procedures were run to identify detail: 1. Identify areas of high variance 2. Find edges 3. Apply a convolution filter 1. 2. 3. 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 59

ImageJ Collection - Apply Subtraction & Filters Additional processes brought out more detail: 1. Subtract the background leaving white areas 2. Adjust shadows for south west shift 3. Apply a sharpening filter 1. 2. 3. 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 60

ImageJ Christmas Collection - Contrast & Gamma 1. Two Additional processes were applied: 1. Enhance Contrast 2. Adjust Gamma to 1.0 2. 2/17/10 Copyright © Nick D. Barzelay, 2006. All rights reserved. 61

Digital Imaging Study

by Nick Barzelay

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