CS 547 Digital Imaging Lecture 2

Transcription

1 CS 547 Digital Imaging Lecture 2 Basic Photo Corrections & Retouching and Repairing Selection Tools Rectangular marquee tool Use to select rectangular images Elliptical Marque Tool Use to select elliptical or circular images Shift Select perfect circle Alt Select center elliptical Alt Shift Select - center circle Lasso Tool Free form tool for making selections Click hold and drag Polygon Lasso Tool Use when you have straight lines Selection Tools Used the Most Magnetic Lasso Tool Lets you isolate complex shapes Selects between the difference in colors Hit backspace to backup Magic Wand Tool Works best when there is a lot of consistent color Quick Selection As you drag, the selection expands outward and automatically finds and follows defined edges in the image. Creates a selection based on all layers instead of just the currently selected layer. Which Selection Marque tool to use?

2 Eight General Steps for Retouching 1. Make a copy of the original and work with the copy 2. Check that the resolution is appropriate 3. Crop 4. Repair flaws (rips, dust, or stains) 5. Adjust contrast and tonal range 6. Adjust - Remove color casts 7. Adjust color and tone (highlights, midtones, shadows, and desaturation) 8. Sharpen Note: You should complete these process in order Resolution Image resolution the number of pixels per unit length in an image Measured in ppi (pixels per inch) resolution # pixels file size Monitor resolution the number of pixels per unit length on a monitor (ppi) Printer (output) resolution the number of dots per inch (dpi) produced dpi Quality Resolution Web: 72 dpi. Print: 150 dpi Photos: 300 dpi Pixels Quality Inches Resolution Pixels Size 5 x 7 72 dpi 360 x K 5 x dpi 750 x M 5 x dpi 1500 x M Cropping an image 1. Select the Crop tool ( ) 2. Drag within an image to create a cropping marquee 3. Adjust the cropping marquee so that it will crop the material you want 4. Tilt the cropping marquee to straighten 5. Press Enter or (Option Bar) or Image>crop Note: Use the trim command (Image > Trim) to get rid of any left over border

3 Retouching tools Spot Healing Brush tool (Blends) Removes blemishes and imperfections Blends with surroundings Healing Brush tool (Blends with Sample) Corrects imperfections, causing them to disappear into the surrounding image. Good for wrinkles. Requires a sample spot (alt-click) Matches the texture, lighting, transparency, and shading of the sampled pixels to the pixels being healed. ] [ - Increase / Decrease brush size Content- Aware Fill Technology Magically fills in the space left behind as if the removed content never existed. Content Aware Heal Use Spot Healing Brush Choose Content Aware on option bar. Works well for small areas Content Aware Fill Use the Edit > Fill command (Shift Backspace) Works better on large areas Blending Tool - need to be careful around edges Retouching tools Patch Tool (Blends with sample) Removes blemishes and imperfections 1. Select an area to be fixed 2. Then drag the patch to a sampled area. Requires a sample spot Clone Stamp tool (Replaces with sample) Uses pixels from one area of an image to replace pixels in another part of the image. Requires a sample spot (alt-click) ] [ - Increase / Decrease brush size Retouching tools Summary Retouching Tool Requires Sample Spot Blends Spot Healing Brush X Healing Brush X X Patch X X Replace Clone Stamp X X

4 Adjusting Color in Photoshop Photoshop provides various method to modify color, exposure, tint, and tonal range. 1. Image > Adjustments (Menu bar) 2. Tools 3. Camera Raw Bridge > RC Image > Open in Camera Raw 4. Layer Adjustments (Panels) Image Adjustments Auto Color Removes Color Cast - imbalanced colors or tint Great for old color pictures Shadow/Highlight Corrects images with strong backlighting or wash outs. Useful for brightening areas of shadow in an otherwise well-lit image. Tonal Range the amount of contrast -Is determined by the distribution of pixels, ranging from the darkest pixels (black) to the lightest pixels (white). Narrow Tonal Range Wide Tonal Range Gamma Value affects how light or dark an image looks in a web browser. Affects the appearance of your computer screen by defining a midpoint for gray. Auto Contrast Remaps the darkest and lightest pixels in the image to black and white. Highlights appear lighter & Shadows appear darker. Can improve appearance of many photographic or continuous-tone images Does not improve flat color images Auto Tone - automatically adjust the black point and white point in an image. The intermediate pixel values are redistributed proportionately. May remove color or introduce color casts.

5 Adjusting the color in Camera Raw Bridge > RC Image > Open in Camera Raw Tint Exposure Contrast Saturation Can Not open PSD(s) in Camera Raw Hue / Saturation adjust the hue, saturation, and brightness of a specific color component in an image or simultaneously adjust all the colors in an image. Hue color Hue Slider changes color Saturation purity of the color Saturation slider changes the intensity of the current hue selected. Lightness how much white or black is in the image Good for fine-tuning colors in a CMYK image so that they are in the gamut (range of colors) of an output device. Sponge Tool Used to make small saturation changes Saturation purity / intensity of a color (hue) Options Bar: Saturate - Intensifies the color Desaturate - Dilutes the color When an image is in Grayscale mode, the tool increases or decreases contrast Replacing a color in Photoshop Image > Adjustment > Hue/Saturation Replace Color Color Replacement Tool Adjustment Layer Hue/Saturation

6 Unsharp Mask Sharpens an image by increasing the contrast along pixel edges. Filter > Sharpen > Unsharp Mask Sharpening effects the entire object Tip: use a mask to select the edges only Amount slider determines how much to sharpen Unsharp Mask (cont) Radius slider - defines the number of pixels surrounding the edge pixels that affect the sharpening. The greater the radius value, the wider the edge effects and the more obvious the sharpening. ( Radius Sharper) Threshold slider - defines how different the pixels must be from the surrounding area to be sharpened by the filter. For example, a threshold of 4 affects all pixels that have tonal values that differ by a value or 4 or more, on a scale of 0 to 255. So, if adjacent pixels have tonal values of 128 and 129, they are not affected. Reproducing Colors Monitor Colors RGB (Red, Green, & Blue) Image > Mode > RGB Color Additive colors combine to produce white 255, 255, 255 = White Process Colors (printed colors) CMYK (Cyan, Magenta, Yellow, & Black) Image > Mode > RGB Color Subtractive colors subtract to produce black 0%, 0%, 0%, 0% - White Eight General Steps for Retouching 1. Make a copy of the original and work with the copy 2. Check that the resolution is appropriate 3. Crop 4. Repair flaws (rips, dust, or stains) 5. Adjust contrast and tonal range 6. Adjust - Remove color casts 7. Adjust color and tone (highlights, midtones, shadows, and desaturation) 8. Sharpen Note: You should complete these process in order