style="font-size:15px;"> Here’s one major difference between Photoshop and other programs. Almost all programs have some form of Undo, enabling you to reverse the most recent command or action (or mistake). Photoshop also has, however, a great feature that lets you partially undo. The History Brush tool can partially undo just about any filter, adjustment, or tool — by painting. You select the History Brush, choose a history state (a stage in the image development) to which you want to revert, and then paint over areas of the image that you want to change back to the earlier state.
You can undo as far back in the editing process as you want, with a couple of limitations: The History panel (where you select the state to which you want to revert) holds only a limited number of history states. In the Photoshop Preferences ⇒ Performance pane, you can specify how many states you want Photoshop to remember (to a maximum of 1,000). Keep in mind that storing lots of history states takes up computer memory that you might need for processing filters and adjustments. That can slow things down. The default of 50 history states is good for most projects, but when using painting tools or other procedures that involve lots of repetitive steps (such as touching up with the Dodge, Burn, or Clone Stamp tools), a larger number (perhaps as high as 200) is generally a better idea.
The second limitation is pixel dimensions. If you make changes to the image’s actual size (in pixels) with the Crop tool, the Image ⇒ Crop command, or the Image Size or Canvas Size commands (both in the Image menu), you cannot revert to prior steps with the History Brush tool. You can choose as a source any history state that comes after the image’s pixel dimensions change but none that come before.
Here’s one example of using the History Brush as a creative tool. You open a copy of a photograph in Photoshop. You edit as necessary. You use the Black & White adjustment on the image to make it appear to be grayscale. In the History panel, you click in the left column next to a snapshot (a saved history state) or the step prior to Black & White to designate that as the source state, the appearance of the image to which you want to revert. You select the History Brush tool and paint over specific areas of the image to return them to the original (color) appearance (see Figure 1-5). There you have it — a grayscale image with areas of color, compliments of the History Brush tool!
FIGURE 1-5: Painting to undo with the History Brush, with the original in the upper-right.
Photoshop has another very powerful partial Undo in the Fade command. Found in the Edit menu, Fade can be used immediately after just about any tool or adjustment or filter or, well, almost anything that changes the appearance of the image. (You can even fade the History Brush tool.) The Fade command enables you to change the opacity, blending mode, or both of whatever alteration you most recently made to the appearance of your artwork with tools or commands. You might, for example, use a Sharpen filter and then use the Fade command to change the filter’s blending mode to Luminosity. That’s the functional equivalent of sharpening the L channel in Lab color mode without having to switch color modes at all. Keep in mind that when I use the word immediately, I really mean it — you can’t even use the Save command between applying a filter and using the Fade command.
Installing Photoshop: Need to know
If you haven’t yet installed Photoshop, here are a few points to keep in mind:
Install only into the default location. Photoshop is a resource-intensive program. Using the Creative Cloud Manager to install it into the default location (harddrive ⇒ Applications on a Mac and C:\Program Files for Windows) ensures that it has access to the operating system and hardware as necessary. Installing into any other location or attempting to run Photoshop across a network can lead to frustrating problems and loss of work in progress.
Disable all spyware and antivirus software before installing. Antivirus software can intercept certain installation procedures, deeming them to be hazardous to your computer’s health. That can lead to malfunctions, crashes, lost work, frustration, and what I like to call Computer Flying Across the Room Syndrome. If you use antivirus software (and if you use Windows, you’d better!), turn it off before installing any program, especially one as complex as Photoshop. You might find the antivirus program’s icon in the Windows taskbar; or you might need to go to the Start menu, choose All Programs to locate the antivirus software, and disable it. On Mac, check the Dock. And don’t forget to restart your antivirus software afterward! If you already installed Photoshop and antivirus software was running at the time, I urge you to uninstall and reinstall.
If you use auto-backup software, shut it down, too. It’s best not to run auto-backup software when installing software. Like antivirus software, it can also lead to problems by interfering with the installer.
If you have third-party plug-ins, install them elsewhere. Third-party plug-ins — those filters and other Photoshop add-ons that you buy from companies other than Adobe — can be installed into a folder outside the Photoshop folder. You can then make an alias (Mac) or shortcut (Windows) to that folder and drag the alias/shortcut to Photoshop’s Plug-Ins folder. Why install outside the Photoshop folder? Should you ever need to (gasp!) reinstall Photoshop, you won’t need to reinstall all your third-party plug-ins. Just create a new alias/shortcut and move it into Photoshop’s new Plug-Ins folder. And don’t forget to go to the plug-ins’ websites to see whether the manufacturers offer updates!
If you have lots of plug-ins, create sets. Plug-ins require random–access memory (RAM) (computer memory that Photoshop uses to process your editing commands). If you have lots of plug-ins, consider dividing them into groups according to how and when you use them. Sort (or install) them into separate folders. (Hint: Plug-ins that you use in many situations can be installed into multiple folders.) When you need to load a specific set, swap out the alias or shortcut in the Plug-Ins folder and restart Photoshop.
If you love fonts, use a font-management utility. If you have hundreds of fonts (over the years, I’ve somehow managed to collect upward of 12,000 fonts), use a font-management utility to create sets of fonts according to style and activate only those sets that you need at any given time. Too many active fonts can choke the Photoshop type engine, slowing performance. The Mac OS has Font Book built right in, or you can use the excellent Suitcase Fusion (Mac and Windows) from Extensis (www.extensis.com).
Chapter 2
Knowing Just Enough about Digital Images
IN THIS CHAPTER
In the early days of photography, some less-advanced cultures viewed a photo with great suspicion and even fear. Was that an actual person, trapped in the paper? Did taking a photo steal a person’s soul? You know that a camera doesn’t trap anyone inside the paper — and you can be pretty sure about the stolen soul issue — but how much does the average
