Sử dụng photoshop cs5 part 34 pot

ptg 206 Chapter 13 When performing adjustments, please consider these suggestions: ➤ Make sure your monitor is properly calibrated rst (see pages 7–9). Also learn how to create a soft proof of your document so you can get an inkling of how it will look when printed (see pages 404–405. ➤ Digital photos are captured in RGB Color mode automatically. Keep them in this mode for adjustments. Should you need to adjust an image for a specic CMYK output device, do so on a copy of the le, not on the original. (e docu- ment color mode of high-resolution CMYK scans shouldn’t be changed, either.) ➤ Put your document into Standard Screen mode (choose that option from the Screen Mode menu on the Application bar); Mac OS users should also display the Application frame. e gray area around the image will provide a good neutral backdrop for judging your color and tonal corrections. Correcting tonal values using a Levels adjustment layer Now that you know how a read a histogram (see pages 203–204), you’re ready to create a Levels adjustment layer. Levels has a histogram of its own. We usually use Levels when we rst bring a photo into Photoshop, then sometimes use it again during the course of editing. In the following steps, you will use Levels to correct tonal values (Levels is also used on pages 220–221 and page 232). To correct tonal values using Levels: 1. Click a layer that needs a contrast adjustment, A then on the Adjustments panel, click the Levels button. e Levels controls display. 2. Do any of the following: B To intensify the contrast, brighten the highlights by moving the white Input Levels high lights slider to the left and darken the shadows by moving the black Input Levels shadows slider to the right. Any pixels located to the left of the black slider will become black; any pixels located to the right of the white slider will become white. (is shifting of tonal values is called “clipping.”) Another way to gure out where to position the highlights and shadows sliders is to activate  r e s h o l d m o d e , a t e m p o r a r y , h i g h - c o n t r a s t A  e o r i g i n a l i m a g e l a c k s c o n t r a s t ( l o o k s d u l l ) . B  e h i s t o g r a m i n t h i s L e v e l s p a n e l d o e s n ’ t e x t e n d a l l the way to the edges, an indication that the tonal range of this photo is narrow. To expand the range, we moved the shadows and highlights Input Levels sliders inward to align with the outer edges of the histogram, and moved the midtones slider to the right to darken the midtones. Midtones HighlightsShadows Output Shadows Output Highlights Input Levels sliders Output Levels sliders ptg Adjustments in Depth 207 display of clipping. Alt-drag/Option-drag the highlights slider, and release the mouse when only a few areas of color or white display; A these pixels will become the lightest tonal value. Also Alt-drag/Option-drag the shadows slider, releas- ing the mouse when only a few areas of color or black appear; B these pixels will become the darkest tonal value. 3. With the shadows and highlights sliders now in their proper positions, move the gray Input Levels midtones slider to lighten or darken the midtones separately from the shadows or highlights. C–D ➤ To apply the current Levels settings to other open images (perhaps images that were taken under similar lighting conditions, that require the same adjustments), choose Save Levels Preset from the Adjustments panel menu. Enter a name for the preset (keep the default location), then click Save. Click another document tab, and click an image layer in that document. Expand the Levels Presets list on the Adjustments panel, then click your new preset at the bottom of the list. A Levels adjustment layer will be created, using your saved settings. B  i s i s  r e s h o l d mode as we Alt-drag/ Option-drag the black Input Levels (shadows) slider. D  e L e v e l s a d j u s t m e n t s e x p a n d e d t h e t o n a l range of the image; now the bars extend from one end of the graph to the other. C Our Levels adjustments improved the contrast (the shadows and highlights are intensied). A  i s i s  r e s h o l d mode as we Alt-drag/ Option-drag the white Input Levels (highlights) slider. ptg 208 Chapter 13 To subtly tweak the brightness or contrast in an image, try using the simple but powerful Brightness/ Contrast controls. To apply a Brightness/Contrast adjustment: 1. Click a layer or the Background. 2. On the Adjustments panel, click the Brightness/Contrast button. e Brightness/ Contrast controls display. 3. Move the Brightness and/or Contrast sliders. A–D ➤ Keep the Use Legacy option for Brightness/ Contrast unchecked, as it would permit tonal levels to be eliminated from the image. With this option o, pixel data from the entire tonal range is preserved; after adjustment, you’ll see evidence in the histogram of only a minor redistribution in tonal values. A  e o r i g i n a l i m a g e l o o k s a b i t d u l l ( i t l a c k s c o n t r a s t a n d the color is undersaturated). B Using the Brightness/Contrast settings shown above, we increased the brightness of the overall image and increased the contrast to make the colors more saturated. C  e s k i n t o n e s i n t h e o r i g i n a l i m a g e look washed out. D Using the settings shown at left, we decreased the brightness of the overall image and then increased the contrast to boost the saturation of the skin tones. Applying a Brightness/Contrast adjustment ptg Adjustments in Depth 209 Applying a Photo Filter adjustment To change the color temperature of a scene (make it look warmer or cooler), photographers use colored lens lters at the time of the shoot. In Photoshop, you can simulate the eect of a camera lter by using a Photo Filter adjustment layer, to neutralize a color cast or to apply a tint (as a special eect). You can choose from 20 preset tints or choose a custom color. When using this feature, go for subtle or extreme, but not in between. To apply a Photo Filter adjustment: 1. Click a layer or the Background. A 2. On the Adjustments panel, click the Photo Filter button. e Photo Filter controls display. B 3. Do either of the following: Click Filter, then from the menu, choose a preset warming or cooling lter or a lter color. e lter color displays in the swatch. Click the Color swatch, choose a color for the lter from the Color Picker (note the change in the image), then click OK. ➤ For a subtle change, pick a related color; for a more obvious change, pick a complemen- tary color (opposite on the color wheel). 4. Using the Density slider or scrubby slider, choose an opacity percentage for the tint. Try a modest value between 10% and 25%, or a higher value for a dramatic change. C You can also lower the opacity of the adjustment layer. 5. Check Preserve Luminosity to preserve the overall brightness and contrast of the image. With this option unchecked, the contrast will be softer in the highlights, but the resulting colorization eect may be too pronounced. For a portrait, you may prefer the results with this option o. 6. To compare the original and adjusted images, click the Layer Visibility button on the Adjustments panel o and then on again (or do likewise with the visibility button for the adjustment layer on the Layers panel). A  e o r i g i n a l image has a magenta cast. B For our Photo Filter adjustment layer, we chose Cyan from the Filter menu and left the Density at 25%. C  e P h o t o F i l t e r a d j u s t m e n t r e m o v e d t h e magenta cast but preserved the warm tones from the afternoon sun. ptg 210 Chapter 13 A quick and dirty method for correcting over- or underexposure For a quick and dirty way to correct an over- or underexposed photo, create an adjustment layer, choose a blending mode for the layer that has a light- ening or darkening eect, then duplicate it a few times. It’s not the most precise method in the world, but if it works, it works (and if it makes your art director happy, maybe you can go home early!). To correct the exposure via the Layers panel: 1. Open an over- or underexposed photo, A and click the Background or a layer. 2. On the Adjustments panel, click the Levels button. Leave the settings as they are. 3. On the Layers panel, click the new adjust- ment layer, then choose a blending mode that produces a lightening or darkening eect. For example, to darken an overexposed image, you could try Multiply mode, or to lighten an under- exposed image, try Screen or Lighten mode. 4. If the image is still too light or dark, duplicate the adjustment layer by pressing Ctrl-J/Cmd-J. B Repeat the shortcut until you reach a point where the image is slightly overcorrected and you need to step it back a bit. 5. Lower the opacity of the topmost adjustment layer until the exposure looks just right. C A  e o r i g i n a l i m a g e i s u n d e r e x p o s e d . B We created an adjustment layer, chose Screen blending mode, duplicated the layer, then lowered the opacity of the duplicate adjustment layer to 47%. C  e t w o L e v e l s a d j u s t m e n t l a y e r s p r o d u c e d t h i s r e s u l t . ptg Adjustments in Depth 211 Dodging and burning small areas To lighten or darken pixels by hand in small areas, you might instinctively reach for the Dodge and Burn tools. However, those tools, even with their new enhancements, permanently alter layer pixels. A better method is to dodge and burn areas with the Brush tool on a removable, editable neutral color layer, as in the steps below. To dodge and burn areas via a neutral color layer: 1. If the document isn’t in RGB Color mode, convert it by choosing Image > Mode > RGB Color. 2. Click an image layer or the Background, A then Alt-click/Option-click the New Layer button. e New Layer dialog opens. 3. Choose Mode: Overlay, check Fill with Overlay- Neutral Color (50% gray), then click OK. 4. Choose the Brush tool (B or Shift-B). From the Options bar, choose a Soft Round brush and an Opacity of 20%. Press [ or ] to set the brush diameter. 5. Press D to make the Foreground color black, then apply brush strokes to areas that you want to darken. To lighten areas, press X to swap the Foreground and Background colors (make the Foreground color white), then apply strokes. B–C 6. Optional: To remove any unwanted dodge or burn strokes, hide the image layer. Alt-click/Option- click to sample the gray value in an untouched area, then with a brush opacity of 100%, paint over those strokes. Redisplay the image layer. ➤ To lessen the whole dodge or burn eect, click the neutral gray layer on the Layers panel, then lower the layer opacity or choose Soft Light as the layer blending mode. B When displayed by itself, a neutral gray layer looks like this. …then applied white strokes to lighten the cobblestones around the gure. We applied black strokes to darken the shadows on the sides of the buildings,… C We applied strokes to the neutral gray layer to dodge the road and burn the houses, then lowered the layer opacity to 78% to soften the eect. A  e c e n t r a l  g u r e i n t h i s i m a g e , w h e r e t h e f o c a l point should be, lacks contrast. We’ll adjust the reected light on the cobblestones to draw more attention to that area. . layer. Levels has a histogram of its own. We usually use Levels when we rst bring a photo into Photoshop, then sometimes use it again during the course of editing. In the following steps, you. it look warmer or cooler), photographers use colored lens lters at the time of the shoot. In Photoshop, you can simulate the eect of a camera lter by using a Photo Filter adjustment layer,