Sử dụng photoshop cs5 part 3 pps

ptg creating fi les IN THIS CHAPTER Buying, and choosing settings for, a digital camera . . . . . . . . . . . . . 18 Working with 16 bits per channel . . . 19 Calculating the correct fi le resolution . . . . . . . . . . . . . . . . . 20 Creating a new, blank document . . . . 21 Creating document presets . . . . . . . . 23 Saving your fi le . . . . . . . . . . . . . . . 24 Using the Status bar . . . . . . . . . . . . 27 Ending a work session . . . . . . . . . . . 28 2 We start this chapter with a few basic pointers for buying a digital camera and shooting digital photos. Following that, you’ll learn how to calculate the correct resolu- tion for a le, create a new blank document, create document presets, save and copy your les, use the Status bar, and close up shop. In the next chapter, you will learn how to download photos from your camera and how to use Bridge to open and manage les. In Chapter 4, you will learn how to open and correct your photos using the Camera Raw plug-in before opening them into Photoshop. Although Photoshop lets you create, open, edit, and save les in over a dozen dierent formats, A–B on a frequent basis, you’ll probably encounter or use only a handful of those formats, namely Photoshop (PSD, the native Photo shop le format), Photoshop EPS, Photoshop PDF, JPEG, and TIFF. e Large Document format, or PSB (nicknamed “Photoshop Big”), is used only for huge les; see the sidebar on page 22. Because Photo shop reads so many dierent le formats, you can use the program to open images from many sources, such as digital cameras, scanners, drawing applications, and video captures. You can edit a single image, create a montage of imagery from mul- tiple les, or create images entirely within Photoshop by using brushes, lters, and other commands. Continued on the following page A Files can be saved in these formats in Windows. B Files can be saved in these formats in the Mac OS. ptg 18 Chapter 2 Buying a digital camera If you’re shopping for a digital camera, the rst step is to gure out which model suits your output requirements and, of course, your budget. Two fac- tors to consider in this regard are a camera’s mega- pixel value and the size of its digital light sensor. Camera manufacturers usually list the resolution of a model as width and height dimensions in pixels (such as 3000 pixels x 2000 pixels). Multiply the two values, and you’ll arrive at a number in the millions, which is the number of pixels the camera captures in each shot. is is known as the camera’s megapixel value. If your camera captures a su- cient number of pixels, you’ll be able to print high- quality closeups and enlargements of your photos. Compact, inexpensive “point-and-shoot” cam- eras oer few or no manual controls and have a resolution of 6 to 10 megapixels. ey capture enough detail to produce decent-quality 5" x 7" prints but not larger, and acceptable Web output. Advanced amateur camera models have a resolu- tion of 8 to 12 megapixels. You can get high-quality 8" x 10" prints from these cameras, and they oer more manual controls. Professional camera models (such as digital SLRs) have a resolution of 12 megapixels or higher and can produce high-quality 11" x 14" prints or larger — but they’re costly. More importantly, the digital light sensors in such cameras are larger and more sensitive than those in lesser cameras. ey record more precise detail and produce a higher-quality image, with less visual noise. High- megapixel cameras with large sensors aren’t for everyone — and not just because of their price tag. Images with a high megapixel count have larger le sizes, take longer to upload from the camera to the computer, and require a larger hard drive for stor- age. (See our comparison of megapixels and print size on page 22.) Unless you tend to crop your photos or output large prints, an 8- to 10-mega- pixel camera will be better suited to your needs. Aside from the megapixel count and the size of the sensor, make sure the camera you buy can accommodate a wide assortment of lenses. For more advice about buying a camera, you can visit the website for PC Magazine (pcmag.com) or Macworld (macworld.com). Photography magazine websites are also good sources of information. Choosing settings in your digital camera You’ve acquired a camera (congratulations!) — now you may want some pointers on how to use it. To get good-quality photographs, in addition to establishing the right lighting conditions, compos- ing the shot artistically, etc., you need to choose your camera settings wisely. Here are some basic guidelines: ➤ Medium- and high-end digital cameras let you choose an ISO setting, which controls the sensitivity of the camera’s digital sensor to light (and is comparable to lm speed in lm photography). High ISO settings tend to produce digital noise in low-light areas, so it’s best to choose the lowest ISO setting that still enables you to get the desired exposure. ➤ Decide whether to have your camera capture the photos in the JPEG format (see pages 425– 426), or even better, as unprocessed raw les.* ➤ Choose a color space for your camera: sRGB for onscreen or Web output, or Adobe RGB for print output. ➤ For JPEG photos, choose a white balance set- ting that’s appropriate for the lighting condi- tions in which the photos will be shot; the camera will process the image data based on this setting. For raw les, you can ignore the white balance setting, as the images won’t be processed inside the camera. ➤ If your camera has a histogram display, use it to verify that your shot was taken with the correct exposure settings (aperture and shutter speed). In an overexposed image, insucient details are captured in the highlight areas; in an underexposed image, insucient details are captured in the shadow areas. Photoshop can process and adjust only the details that your camera captures. (For a discussion of histograms, see pages 203–204.) Regardless of whether you shoot JPEG or raw photos, most exposure deciencies, color casts, and other imaging problems can be corrected via the Camera Raw dialog (see Chapter 4) and then the photo can be further corrected via an assortment of adjustment commands in Photoshop. *Each camera model produces its own variation of a raw le. In this book, we refer to such les collectively as “raw les.” Buying, and choosing settings for, a digital camera ptg Creating Files 19 Working with 16 bits per channel To get good-quality output from Photoshop, a wide range of tonal values must be captured at the outset. e wider the dynamic range of your chosen input device, the ner the subtleties of color and shade it can capture. Most advanced amateur and professional digital SLR cameras cap- ture at least 12 bits of accurate data per channel. Like cameras, scanners range widely in quality: Consumer-level scanners capture around 10 bits of accurate data per channel, whereas the high-end professional ones capture up to 16 bits of accurate data per channel. Shadow areas in particular are notoriously dif- cult to capture well. But if your camera can cap- ture 12 to 16 bits per channel (or you work with high-resolution scans), you will have a head start, because your les will contain an abundance of pixels in all levels of the tonal spectrum. Photoshop can process les that are in 8, 16, or 32 Bits/Channel mode. All Photoshop commands are available for 8-bit les. Most Photoshop com- mands are available for 16-bit les (e.g., on the Filter menu, the Liquify and Lens Correction lters are available, as are some or all of the lters on the Blur, Noise, Render, Sharpen, Stylize, and Other submenus, whereas lters on the other submenus are not). Too few Photoshop commands are avail- able for 32 Bits/Channel les to make such les a practical choice. Although you can lower the bit depth of your les via the Image > Mode submenu, it’s better to keep them in 16 Bits/Channel mode. e edit- ing and resampling commands in Photoshop can degrade the image quality, but the extra pixels in 16-bit images make this less of a problem. A–B e tonal adjustment commands in particular, such as Levels and Curves, remove pixel data and alter the distribution of pixels across the tonal spectrum. Signs of pixel loss from destructive edits will be more visible in a high-end print of an 8-bit image than in a 16-bit image. Because 16-bit images con- tain an ample number of pixels in all parts of the tonal spectrum at the outset, more tonal values are preserved, and the resulting output is higher quality. To summarize, these are some basic facts about 16-bit les to consider: ➤ Photoshop can open 16-bit les in CMYK or RGB mode. ➤ 16-bit les can be saved in many formats, such as Photoshop (.psd), Large Document (.psb), Photoshop PDF (.pdf), PNG (.png), TIFF (.tif), and JPEG 2000 (.jpf). ➤ From the Mac OS, you can print 16-bit les, provided your printer supports 16-bit printing. ➤ For commercial print output, your output service provider may request 8-bit les, in which case you will need to convert them after image-editing. Note: If system or storage limitations prevent you from working with 16-bit images, consider follow- ing this two-stage approach: Perform the initial tonal corrections (such as Levels and Curves adjust- ments) on the 16-bits-per-channel image, then convert it to 8 bits per channel for further editing. B Here, the same Levels adjustment was made to a 16-bit version of the same image. Because of the higher bit depth, the smooth tonal transitions were preserved. A As a result of a Levels command adjustment to this 8-bit image, some image data was discarded, as shown by the spikes and gaps in the histogram. ptg 20 Chapter 2 Calculating the correct file resolution Resolution for print If you shoot digital photos, your camera will preserve either all the pixels that are captured as raw les or a portion of the pixels that are captured as small, medium, or large JPEG les. If you use a scanner to acquire images, you can control the number of pixels the device captures by setting the input resolution in the scanner software. High-resolution photos contain more pixels, and therefore ner details, than low-resolution photos, but they also have larger le sizes, take longer to render onscreen, require more processing time to edit, and are slower to print. Low-resolution images, however, look coarse and jagged and lack detail when printed. Your les should have the minimum resolution to obtain the desired output quality from your intended output device at the desired output size — but not much higher. ere are three ways to set the resolution value for your digital les. ➤ If you open raw digital or JPEG photos into the Camera Raw dialog, which we highly recommend, you can specify an image resolution there. See page 66. ➤ After opening your les into Photoshop, you can change the image resolution in the Image Size dialog (see pages 122–124). ➤ When scanning photos, you’ll set the image resolution using the scanning software for that device. e print resolution for digitized images (from a camera or scanner) is calculated in pixels per inch (ppi). A–C For output to an inkjet (desktop) printer, the le resolution should be between 240 and 300 ppi. Commercial print shops have specic require- ments for their particular output devices, so it’s important to ask them what resolution and halftone screen frequency settings they’re going to use before choosing a resolution for your les. For a grayscale image, the proper resolution will usually be around one-and-a-half times the halftone screen frequency (lines per inch) setting of the output device, or 200 ppi; for a color image, the resolution will be around twice the half tone screen frequency, or 250–350 ppi. A 72 ppi B 150 ppi C 300 ppi ptg Creating Files 21 Resolution and dimensions for the Web Choosing the correct le resolution for Web output is a no-brainer: It’s always 72 ppi. Choosing the correct dimensions for Web output requires a little more forethought, because it depends on how your Photoshop images are ulti- mately going to be used in the Web page layout. To quickly create a document with the proper dimen- sions and resolution for Web output, choose a preset in step 3 at right. To determine a maximum custom size for a Photoshop image to be displayed on a Web page, rst estimate how large your user’s browser window is likely to be, then calculate how much of that window the image is going to ll. Currently, the most common monitor size is 1024 pixels wide by 768 pixels high. Most viewers have their browser window open to a width of approxi- mately 1000 pixels. If you subtract the space occupied by the menu bar, scroll bars, and other controls in the browser interface, you’re left with an area of up to 800 x 600 pixels; you can use those dimensions as a guideline. If your Photoshop le is going to be used as a small element in a Web page layout, you can choose smaller dimensions. Creating a new, blank document In these instructions, you will create a new, blank document. You can drag and drop or copy and paste imagery into this document from other les, or draw or paint imagery by hand using brushes. e images can then be edited with Photoshop commands, such as eects and lters. To create a new, blank document: 1. Choose File > New (Ctrl-N/Cmd-N). e New dialog opens. A 2. Type a name in the Name eld. 3. Do either of the following: Choose a preset size option from one of the three categories on the Preset menu: the Default Photoshop Size; a paper size for com- mercial and desktop printers; or a screen size for Web, mobile, lm, and video output. Next, choose a specic size for that preset from the Size menu. Choose a unit of measure from the menu next to the Width eld; the same unit will be chosen automatically for the Height (or to change the unit for one dimension only, hold down Shift while choosing it). Next, enter custom Width and Height values (or use the scrubby sliders). Continued on the following page A In the New dialog, enter a le Name; either choose a Preset size or enter custom Width, Height, and Resolution values; choose RGB Color Mode and a Background Contents option; and choose a Color Prole. ptg 22 Chapter 2 4. Enter the Resolution required for your target output device — be it an imagesetter or the Web. For the Web, enter 72; for print output, see our discussion of resolution on page 20. You can use the scrubby slider here, too. 5. Choose a document Color Mode (RGB Color is recommended), then from the adjacent menu, choose 8 bit or 16 bit as the color depth (see page 19). You can convert the image to a dier- ent color mode later, if needed (see “Photoshop document color modes” on pages 3–4). 6. Note the Image Size, which is listed on the right side of the dialog. If you need to reduce that size, you can choose smaller dimensions, a lower resolution, or a lower bit depth. 7. For the Background of the image, choose Background Contents: White or Background Color; or choose Transparent if you want the bottommost tier of the document to be a layer. (To choose a Background color, see Chapter 11. To learn about layers, see Chapter 8.) 8. Click the Advanced arrowhead, if necessary, to display additional options, then choose a Color Profile. is list of proles will vary depend- ing on the document Color Mode. (Note: you can also assign or change the prole later in the Edit > Assign Prole dialog. To learn more about color proles, see pages 10–11 and 16.) For Web or print output, leave the Pixel Aspect Ratio on the default setting of Square Pixels. For video output, choose an applicable option (see Photoshop Help). 9. Click OK. A new, blank document window appears onscreen. To save it, see page 24. ➤ To force the New dialog settings to match those of an existing open document, open the New dialog, then from the bottom of the Preset menu, choose the name of the document that has the desired dimensions. ➤ If the Clipboard contains graphic data (say, that you copied from Adobe Photoshop or Illustrator), the New dialog will automati- cally display the dimensions of that content. Choosing Clipboard from the Preset menu in the New dialog accomplishes the same thing. If you want to prevent the Clipboard dimensions from displaying, and display the last-used le dimensions instead, hold down Alt/Option as you choose File > New. MEGAPIXELS, RESOLUTION, AND PRINT SIZES Image Megapixels in Inches (rounded off) * Resolution 6 8 10 12 150 ppi 13 x 20 16 x 22 17 x 24 18 x 28 300 ppi 7 x 10 8 x 11 8 x 13 9 x 14 * ese print sizes are approximate. For a more exact list- ing, search the Web for “megapixels to print size chart.” PHOTOSHOP BIG In Photoshop, you can create and save fi les as large as 300,000 x 300,000 pixels — or over 2 gigabytes (GB) — a n d t h e y c a n c o n t a i n u p t o 5 6 u s e r - c r e a t e d c h a n - nels. The Large Document (.psb) format is designed specifi cally for saving these gonzo fi les, but they can be opened and edited only in Photoshop (versions CS through CS5). What can you do with PSB fi les? If you have the disk space to store and work with them and have access to a wide-format printer that can output super-large images (up to 32,000 x 32,000 pixels), great. In order to output a PSB fi le on an ordinary printer, though, you would have to lower its resolu- tion drastically (remember to duplicate the fi le fi rst). . of those formats, namely Photoshop (PSD, the native Photo shop le format), Photoshop EPS, Photoshop PDF, JPEG, and TIFF. e Large Document format, or PSB (nicknamed Photoshop Big”), is used. levels of the tonal spectrum. Photoshop can process les that are in 8, 16, or 32 Bits/Channel mode. All Photoshop commands are available for 8-bit les. Most Photoshop com- mands are available. ppi 13 x 20 16 x 22 17 x 24 18 x 28 30 0 ppi 7 x 10 8 x 11 8 x 13 9 x 14 * ese print sizes are approximate. For a more exact list- ing, search the Web for “megapixels to print size chart.” PHOTOSHOP