Tài liệu Adobe Photoshop 7.0 for Photographers- P6 doc

Adobe Photoshop 7.0 for Photographers 230 Figure 9.6 Curves corrections can be exactly the same as making a Levels adjustment. In this example, the two ends of the curve have been dragged in as you would in Levels, in order to set the optimum shadow and highlight points. You can control both the lightness and the contrast of the image by adjusting the shape of the curve. Click on the bottom right box to enlarge the curves dialog, as shown below. Figure 9.7 If you click on the horizontal output ramp, the curve point readouts will be displayed using density percentages when in RGB and ink percentages when in CMYK. The curve is also reversed in CMYK, with the shadow point in the top right corner and the highlight point in the bottom left. If you Option/Alt-click anywhere inside the grid area the grid units will switch from 25% to 10% increments. For example, Chapter Fourteen shows how coloring effects can be achieved through individual channel curves adjustments. The default RGB units are measured in bright- ness levels from 0 to 255. CMYK curves are by default displayed differently (click on the horizontal output ramp to toggle between displaying with levels or ink percentage read- outs). This alternate mode (see Figure 9.7) is designed for repro users who primarily prefer to see the output values expressed as ink percentages. The next example shows how you adjust the curve to both improve image contrast and correct the color balance at the same time. Providing the monitor has been cor- rectly calibrated, this can all be judged by eye on the screen. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Color adjustments 231 1 The photograph shown here lacks detail in the shadows. The information is there but in its cur- rent state the hair will print too dark. We don’t want to lighten all of the photograph, otherwise the mood in the original picture will become lost. Choose Image > Adjustments > Curves. The dialog box contains a line on a graph on which you can remap the image tones. Identify which portion of the curve needs adjustment by mous- ing down in the image area (such as on the darker areas of the hair) and watch where the circle appears on the curve. 3 In this corrected version the midtone and high- light tone values remain unaltered, while the shadow detail has been lifted. You can always use Curves in this way to exert fine control over the lightening or darkening at precise points on the tonal scale. 2 Click on the curve line to anchor both the midpoint and the highlights. Now refer back to stage one which helped you determine where to add a point on the shadow end of the curve, click on the curve and drag upwards to lighten. The line bends to form a smooth curve and the shadows are made lighter. Precise positioning of the curve anchor points is achieved by using either the keyboard arrow keys or entering numeric values in the Input and Output boxes below. Client: Schwarzkopf Ltd. Model: Maria at M&P. There is also a more precise way of correcting the color balance. If you exploit the fine tuning capabilities built into the Curves dialog and combine this with the use of the color sampler tool, you can correct with absolute precision. Repro professionals will often rely more on the numeric readouts to judge the color in a digital image. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Adobe Photoshop 7.0 for Photographers 232 1 The above photograph has a cold color cast. This is particularly noticeable in the backdrop, which should be a neutral gray. If I want to cor- rect the color in this picture, the best method is to apply a curves image adjustment. Go to the Image > Adjustments menu and choose Curves 2 This shows you the curves corrected version. The main Curves dialog allows you to make tonal corrections to the composite color channel (in this case, the RGB composite channel). I dragged down from the RGB channel to select first the red color channel and added a couple of control points to the curve to adjust the color balance for the midtones and highlights. If you are not happy about the position of a curve point, it is very easy to move it around and change the shape. When a control point is selected, to select the next point, use Control/Right mouse-click+Tab. To select the previous control point, use Control/ Right mouse-click+Shift+Tab. To get rid of a point altogether, drag it to the outer edge of the graph or Command/Ctrl-click on the point in the grid. I then went to the Blue channel and added a couple of points. This time to correct the color for the shadows and highlights in the Blue channel. Client: Anita Cox Salon. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Adobe Photoshop 7.0 for Photographers 234 To add a new color value as a control point on the curve, Command/Ctrl-click inside the document window and you will see a control point appear on the corresponding portion of the curve. If you use Shift+Command/Ctrl to click in the document win- dow, Control points will be automatically added to all three color channels at once. So when adding control points to color correct the white boot, I would Shift+Command/Ctrl click on top of each of the color sampler points to add these as control points in all three color channels in the Curves dialog. When you are editing the points in the Curves dialog, use Shift-click to select multiple points. As you adjust one control point the others will move in unison. To deselect all the points, use Com- mand/Ctrl-D. When a single point is selected you can select the next point using Control/Right mouse-click+Tab and the previous point by using Control/Right mouse- click+Shift+Tab. 3 The color sample points can be repositioned as necessary by dragging on them with the color sampler (you can access the tool while in an image adjustment dialog, by holding down the Shift key). Apply a Curves adjustment and adjust each color channel curve as necessary. The first RGB read- out figure in the Info palette tells you exactly where to position the point on the curve (see the In- put numeric box). Either manually drag the point or use the keyboard arrows (Shift+arrow key moves the control points in multiples of 10) to balance the output value to match those of the other two channels. What you adjust at one point on the curve will affect the shape and con- sequently the color in another part. This is why it is advisable to monitor the color values across the range of tones from light to dark. Remember that you can shift select image sampled colors to add points to the curve. Photograph: Davis Cairns. Client: Red or Dead Ltd. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Color adjustments 233 2 Follow the Levels adjustment procedure as outlined in the previous chapter (Assigning shadow and highlight points, page 216). Expand the tonal range and neutralize the shadows and highlights as much as possible. This improves the picture already and removes most of the cyan cast. 1 When you have a white object photographed against a white background, any color cast will always be very noticeable. First of all select the color sampler tool and click on the image in up to four places to locate the persistent color read- outs at different places on the boot. The follow-on tutorial, featuring the white boot, is a good example of where the Info palette readout can be used to determine the neutrality of the image tones and is the ultimate guarantee of perfect color correction. If you match up the RGB values so that red = green = blue, the resulting color is always a neutral gray. Remember, this is not the case with CMYK color (see Chapter Four on color management). Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Color adjustments 235 Arbitrary Map mode If you click on the Arbitrary Map mode button in the Curves dialog, you can sketch in the grid area with the pencil cursor to create a freehand curve map shape. The results are likely to be quite repulsive, but if you click on the smooth button a few times you will see the curve become less jagged and the tonal transitions will then become more gentle. Another example of an Arbitrary Map mode curves adjustment can be found in Chapter Thirteen on black and white effects. Client: Anita Cox Salon. Model: Sorcha, Bookings. Figure 9.8 If you click on the Arbitrary Map button in the Curves dialog, you can draw a freehand curve shape like the one shown here. Click on the Smooth button to produce a gentler effect. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Adobe Photoshop 7.0 for Photographers 236 1 This is the before image. Using the Replace Color adjustment command we can quickly take the image information in the purple backdrop and alter the Hue, Saturation and Lightness val- ues. This image adjustment command is not avail- able as an adjustment layer, because the single command is a combined two-stage process which involves making a pixel selection. 2 Choose Image > Adjustments > Replace Color. To make the selection, first click with the eye- dropper either on the image or in the dialog box mask preview window. Click again with the ‘add eyedropper’ icon to add to the selection. Click with the ‘minus eyedropper’ to remove colors. Use the Fuzziness control slider to determine how much tolerance you want to apply to the selection area (see magic wand tool). Now change the Hue/ Saturation values. As you can see here, the biggest change took place with the Hue, making the back- ground go green instead of purple. Small saturation and lightness adjustments were also necessary. Replace Color Hue/Saturation crops up again in the Replace Color command, which is really like a combination of the Select > Color Range and Hue/Saturation command combined in one. With Replace Color, you can select a color or range of colors, adjust the fuzziness of your selection and apply the Hue/Saturation adjustments to those selected pixels only. Alas, the selection made this way is not savable. For critical situations you will want to make a Color Range type selection first and while the selection is active, choose New Adjustment Layer > Hue/Saturation from the Layers palette. This two- step process is probably the more flexible approach. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Color adjustments 237 Figure 9.9 To use Color Range, click in the docu- ment window or dialog preview to sample a color on which to base your selection. The Fuzziness control is like the Tolerance control in the magic wand options. Click on the plus or minus eyedroppers to add or remove colors from the selection. The dialog preview can either display the original image or preview the selection as a mask. The Selection Preview can allow you to view the selection represented as a quickmask. 3 After performing the Replace Color operation, there was a little spill-over on to the blue plate. All you have to do is erase the offending areas – you can use the history brush to do this, then make a circular selection with the elliptical mar- quee tool. The marquee actions can be modified when you hold down the Option/Alt key to draw out from the center and constrained to a circle when you hold down the Shift key at the same time. If at any time you also hold down the Spacebar, you can drag to reposition the selec- tion. If you release the Spacebar (but have still held down the Option/Alt+Shift keys), you can carry on expanding or contracting the selection. Now feather the selection and select the Open image state as the History source and restore the original unaltered image. Photograph: Rod Wynne-Powell. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Adobe Photoshop 7.0 for Photographers 238 Color Range Where the magic wand creates selections solely based on luminosity, the Select > Color Range option creates selections that are based on color values which are simi- lar to the sample pixel color. Among other things, you can use the Color Range command to make a selection based on out-of-gamut colors. This means you can use Color Range to make a selection of all those ‘illegal’ RGB colors outside the CMYK gamut and apply corrections to these pixels only. This task is made easier if you feather the selection slightly and hide the selection edges (View > Hide Extras). Then choose View > Gamut Warning. Adjustments can be made using the Selective Color or Hue/Saturation commands as before. Local areas may also be corrected with the sponge tool set to Desaturate. Adjustment layers Adjustment layers and the Image > Adjustments commands are identical in purpose. Adjustment layers offer the facility to apply multiple image adjustments and/or fills to an image and have these changes remain ‘dynamic’. In other words, an adjustment layer is an image adjustment that can be revised at any time – adjustment layers enable the image adjustment processing to be deferred until the time when the image is flattened. Adjustment layers are automatically ‘layer masked’ layers, which when selected, can be painted upon in black to remove areas from the adjustment effect. Used in conjunction with History, they give Photoshop a three-dimensional work space of not just multiple, but limitless, undos. One potential drawback is that having a lot of adjustment layers in an image may slow down the monitor preview. This slowness is not a RAM memory issue, but to do with the extra calculations that are required to redraw the pixels on the screen. Adjustment layers are savable in the Photoshop native, TIFF and PDF formats. Also note that the threshold preview mode is now enabled in the Levels adjustment layer dialog. Multiple adjustment layers You can have more than one adjustment layer saved in a document, with each producing a separate image adjustment. In this respect, they are very useful because combinations of adjustments can be previewed to see how they will affect a single layer or the whole image before you apply them. You can have several adjustment layers in a file and choose to readjust the settings as many times as you want. It is possible to keep changing your mind and make multiple changes to an adjustment layer without compromising the image quality. The ability to edit adjustment layers and mask them to selectively apply an adjustment provides the most obvious benefit Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Color adjustments 239 over making a series of normal image adjustments. I used to wrongly assume that when you flattened all the adjustment layers, the effect of doing so was as if you had made a single image adjustment. But this is not so. When you flatten an image, Photoshop will apply all the adjustment layers sequentially as if you had made a series of normal image adjustments. Blending mode adjustments 1 You can use the layer blending modes as an alternative method to lighten or darken an image. In this example we have a dark image that needs to be made brighter. Go to the Layers palette and add a new adjustment layer. It does not par- ticularly matter which – in this example I chose Levels. 2 Highlight the adjustment layer and change the blending mode to Screen. The result of this will be the same as if you had made a copied Back- ground layer and set it to Screen blend mode. Screening will make the image lighter and Multi- ply will make the image darker. I then added a gradient to the adjustment layer using the default foreground/background colors. This partially hid the adjustment layer and retained some of the original darker tones at the top of the picture. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. [...]... an Absolute 10% will make the new value 50% 243 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers Chapter Ten Repairing an Image M ost photographers are interested in the potential of using Photoshop as a tool for retouching pictures So we shall start with simple techniques like cloning and then go on to explore some other advanced methods... apply heavy pressure for a full-sized brush 3 Continue using the healing brush to complete the skin tone retouching In this example I sampled one pixel source point for the chest and neck areas and another to retouch the face Client: Thomas Macmillan Model: Sophie Boeson – Models One 253 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers... Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers 2 When you have finished defining the selection for the area you want to patch, make sure that the patch tool is selected in the Tools palette and drag inside the selection to relocate it on an area of texture that you wish to sample from 3 As you release the mouse, Photoshop will commence calculating a healing blend,... transition of color and luminosity with the pixels outside the painting area For this reason there is no need to use a soft edged brush and in fact you will find that you get more controlled results using a hard edged brush 251 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers In practice, the healing brush is able to perfectly blend sampled... adjustments had been applied as before, but the image was in 8 bits per channel mode throughout As you can see, if you keep a picture in 16 bits per channel mode while you apply levels and curves adjustments, much more of the levels data will be preserved as a result 241 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers Selective Color... picture in Photoshop The technique shown here has the advantage of applying the filtered information precisely to fill in the dirty areas without the risk of destroying the tonal values in the rest of the picture 249 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers 1This photograph serves as a good example with which to demonstrate the... size to make the second boat smaller and appear to be further away in the distance 257 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Adobe Photoshop 7.0 for Photographers 4 I then hit Enter just to OK the transformation After that I moused down with the patch tool inside the selection area and moved the selection very slightly If you follow these steps precisely and release.. .Adobe Photoshop 7.0 for Photographers Not many people are aware of the fact that you can make use of the layer blending modes in conjunction with adjustment layers to lighten or darken an image The example on page... command is therefore a tool for correcting CMYK color, but you can also use it to prepare an RGB file before converting it to CMYK The color control available with Selective Color is a bit like adjusting the sound on a music system with a sophisticated graphics equalizer Subtle or quite strong changes can be made with ease to the desired band of color tones The Selective Color command is therefore another... slight time-lag after applying each click or small stroke with the healing brush You can also use a pattern preset as the source for the healing brush You can either choose a pre-loaded preset or create your own The Pattern Maker in the Filter menu in Photoshop 7.0 is ideal for this purpose as you can sample from just a small area of useful texture in an image and use the Pattern Maker to create a randomly . watermark. Adobe Photoshop 7. 0 for Photographers 236 1 This is the before image. Using the Replace Color adjustment command we can quickly take the image information. use the clone stamp at 100 %. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Adobe Photoshop 7. 0 for Photographers 246 with