TechNote (Archived)

Optimize performance of Photoshop (CS on Windows)

What's covered

Adobe Photoshop options and plug-ins

Image files

Operating system software

Hardware

Resources

The performance of Adobe Photoshop is affected most by available random-access memory (RAM) and computer processor speed. Other factors can also affect performance, such as the options you select, system configuration, and the built-in limitations of Photoshop. Photoshop supports a maximum file size of 2 GB and a maximum dimension of 300,000 x 300,000 pixels per image. In addition, Photoshop can access 2 GB of installed physical RAM. To work within these limitations and optimize performance in Photoshop, apply the following recommendations.

Note: Photoshop CS allows for images with a maximum file size of 4 GB for TIFF files, and almost unlimited file sizes for images saved in the new native Large Document Format (.psb). Photoshop CS can access only 2 GB of RAM, so large files will need to use considerable scratch disk space. Large Document Format files cannot be read by Photoshop 7.0.x or earlier.

Adobe Photoshop options and plug-ins

The options you select and plug-ins you use in Photoshop can affect its performance. The options and plug-ins that most directly affect performance include those covered in this section.

Working with the File Browser

The File Browser allows you to view, sort, and process images. Photoshop CS also allows you to tag and sort images, search and edit metadata and keywords, and run batch processes. If you open a folder with numerous images in the File Browser, performance may slow while the File Browser creates a cache of thumbnails for the images in the folder. You can make the following changes to File Browser preferences settings to improve performance: turn off High Quality Previews; reduce the size of images processed by the File Browser; reduce the custom thumbnail size if you've set a larger size than the default; deselect Render Vector Files to prevent Photoshop from creating thumbnails of vector files; turn off background processing.

For more information about the File Browser, see the Photoshop User Guide or Online Help.

16-bit functionality

Photoshop CS significantly increases the number of features that can be performed on 16-bit images. However, if your resources are low, reducing your images to 8-bit can improve performance. Note that this reduction will permanently delete the extra bit data from your image.

Setting scratch disks

The Photoshop scratch disk is similar to virtual memory. For the best performance, you should set the scratch disk to a defragmented hard disk that has plenty of unused space and fast read/write speeds (rather than a network drive or removable media such as a Zip drive). Photoshop requires at least 280 MB of free hard-disk space, but more is recommended. If you have more than one hard disk volume, you should specify additional scratch disks. Photoshop CS supports up to 64 exabytes (EB) of scratch disk space on a total of four volumes. Photoshop 7.x supports up to 4 EB. (An EB is equal to 1 billion gigabytes.) RAID 0 partitions provide the best possible performance as Photoshop scratch disks.

Note: Adobe recommends that you set the primary scratch disk to a different hard disk than the one Windows uses for its virtual memory or paging file.

To set the scratch disk:

1. Choose Edit > Preferences > Plug-Ins & Scratch Disks.

2. Choose the drive that has the most free space from the First pop-up menu.

3. Choose a second drive, if available, from the Second pop-up menu.

4. Choose other drives, if available, from the Third and Fourth pop-up menus.

5. Click OK.

Adjusting the Image Cache

Photoshop uses image caching to redraw high-resolution images faster. With image caching, Photoshop uses low-resolution versions of an image to quickly update the image on-screen as you work. To enable the Image Cache option, specify the number (1 to 8) of low-resolution versions you want Photoshop to store (cache). The more versions of an image you have Photoshop cache, however, the slower it opens image files. In Photoshop, the default Image Cache setting is 4. Setting the Image Cache option to 1 disables image caching; only the current screen image is cached. Setting the Image Cache higher than 4 improves the performance when working on larger images by redrawing them faster.

To adjust the Image Cache setting:

1. Choose Edit > Preferences > Image Cache.

2. Enter a value from 1 to 8 in the Cache Levels text box.

3. Restart Photoshop.

Note: Image caching may cause a less accurate preview. When necessary, view files at 100% to ensure an accurate preview.

Using the Extract command

When you run the Extract command (Image > Extract) on a computer that has low RAM or disk space, Photoshop responds slowly or not at all. The Extract command can require more than the recommended minimum amount of RAM and disk space for Photoshop--if Photoshop responds slowly when you use the Extract command, increase the percentage of memory used by Photoshop, or free additional hard-disk space.

To increase the percentage of memory used by Photoshop:

1. Choose Edit > Preferences > Memory & Image Cache.

2. In the Memory Usagesection, increase the Maximum Used By Photoshop percentage, and click OK.

Note: Don't set the percentage to more than 75%.

3. Restart Photoshop.

Minimizing palette preview thumbnails

Photoshop requires additional memory to display preview thumbnails in the Layers, Channels, and Paths palette. Photoshop updates the preview thumbnails as you make changes to the image itself. The more preview thumbnails Photoshop displays, and the larger the thumbnail you select, the more memory Photoshop requires to draw and update preview thumbnails.

To minimize or turn off palette previews in the Layers, Channels, or Paths palette, select Palette Options from the palette menu. For Thumbnail Size, select the smallest thumbnail size or select None, then click OK.

Using the Detect Watermark plug-in

Photoshop includes the Detect Watermark (Digiopen.8be), Embed Watermark (Digisign.8bf), and Read Watermark (Digiread.8bf) digital watermarking plug-ins, created by Digimarc Corporation. The optional Detect Watermark plug-in scans each image you open for a digital watermark, which increases the time it takes for Photoshop to open the file. When the plug-in detects a watermark, it puts a copyright symbol on the image window's title bar. You can find the source of the image by choosing Filter > Digimarc > Read Watermark.

To disable the Detect Watermark plug-in, locate the Digimarc folder in the Photoshop/Plug-Ins folder, and add a tilde (~) to the beginning of the folder name (for example, ~Digimarc).

Image files

You can optimize your workflow to improve performance by minimizing file size, editing individual channels, and using image compression selectively. Additionally, because layers and channels add significantly to the size of a file, you can minimize file size by merging layers and deleting channels when you no longer need them. And finally, if you are preparing images for color separation, you can work in RGB mode until you are ready to print and then change the images to CMYK mode. When converted from CMYK to RGB, a file's size should decrease by about 25%.

Minimizing file size

You can minimize the size of your files by reducing their resolution, measured in pixels per inch (ppi). Photoshop requires more memory and disk space to process high-resolution images, therefore increasing the time it takes Photoshop to display, process, and print them. Increasing the resolution of an image doesn't always improve the quality of the image, and instead only increases its file size. You want the resolution of your images to be the highest value your printer can use. Resolutions higher than that only add information to your image that your printer can't use, but must process, and thus increase print times.

If you plan to print continuous-tone images (for example, photographs), begin by using a resolution that is 1.5 to 2 times the screen frequency, measured in lines per inch (lpi), that you'll use to print the image. For line-art images, such as drawings, use the same value as your printer's resolution, measured in dots per inch (dpi). For example, if the resolution of your printer is 600 dpi, and you plan to print the image using the printer's default screen frequency of 85 lpi, save continuous-tone images at a resolution between 127 ppi (85 lpi x 1.5) and 170 ppi (85 lpi x 2), and save line-art images at a resolution of 600 ppi.

Recommended resolutions for continuous-tone images:

Output	Recommended resolution
Macintosh monitor	72 ppi
Windows-compatible monitor	96 ppi
300 dpi laser printer	100 ppi
600 dpi laser printer	150 ppi
725 dpi inkjet printer	150 ppi
1200 dpi or higher imagesetter	2x the screen frequency (lpi) value you specified

To reduce the resolution of an image in Photoshop:

1. Open the image, then choose Image > Image Size.

2. In the Image Size dialog box, decrease the Resolution value, then click OK.

Turning off maximize compatibility

The maximize PSD compatibility option in Edit > Preferences > File Handling allows you to save a composite version of your file with the layered version. Although saving the composite allows the most compatibility with your PSD images and previous versions of Photoshop or other applications that can open a PSD file, it also significantly increases the file size of the image. You can set this preference to Never save the composite, Always save it, or to ask to save it each time you save in the PSD format.

Flattening TIFF files

Photoshop allows layers to be saved in TIFF files. Layered TIFF files are larger than flattened TIFF files and require more resources for processing and printing. If you work with a layered TIFF file, save the original layered file as an Adobe Photoshop (*.psd) file; then, when you are ready to save the file in TIFF format, save a copy without layers.

Minimizing the number of layers
Layers make many operations in Photoshop dramatically easier, but they also increase file sizes and redraw time because Photoshop recomposes each later after each change in the image. After you have completed changes to layers, you can flatten (merge) them to reduce a file's size. You should also make sure to remove blank layers from the file since they too increase its size. It is important to remember that Photoshop does not let you separate layers after merging them. Instead, you can either use the Undo command or you can use the History palette to reverse a merge.

-- To flatten all layers in a file, choose Layer > Flatten Image.
-- To merge a layer with the layer below it:
1. In the Layers palette, select the layer above the layer with which you want to merge it.
2. Choose Layer > Merge Down.

Using image compression

Although compressed files generally have small file sizes, Photoshop may take longer to open or save them. With the exception of images saved in Photoshop format, Photoshop must decompress a file to open it and then recompress the file to save it. The BMP, CompuServe GIF, JPEG, Photoshop, Photoshop EPS, Photoshop PDF, and TIFF formats all can be saved with compression. In addition, Photoshop enables you to specify a compression method for TIFF layers in the TIFF Options window. You can improve performance by saving your file in compressed Photoshop format (a compression format in which there is no data loss) as you work, and then save your file in the format you want when you are finished editing the image.

To save an image without compression from Photoshop, choose File > Save As, select the format you want, and then select the "no compression" option in the format's Options dialog box. For example, select the TIFF format, and in the TIFF Options dialog box, select None for Image Compression.

Editing individual channels

Photoshop requires less memory to apply a filter to a single channel than it does to apply a filter to multiple channels or to an entire image (composite channel). In a flattened image, each RGB channel is about one-third the size of the file; each CMYK channel is about one-fourth the size. To edit a single channel, select the channel you want to edit in the Channels palette.

Using the Filter Gallery and applying filters to individual channels

The new Photoshop CS Filter Gallery allows you to test one or more filters on an image before applying the effect(s), which can save considerable time.

Dragging and dropping between files
Dragging and dropping layers or files is more efficient than copying and pasting them. Dragging bypasses the clipboard and transfers data directly. Copying and pasting can potentially involve more data transfer and is much less efficient.

Operating system software

By customizing your operating system so it runs efficiently, you not only increase the amount of system resources available to applications, but also ensure that your applications run efficiently. Optimizing your hard drive and virtual memory, organizing or removing temporary files, and disabling unnecessary applications running in the background improves performance.

Note: Photoshop CS can only operate on computers running Windows 2000 or Windows XP.

Temporary files

When you work in an application, a copy of your data file is stored temporarily on the hard drive. Many applications create .tmp files and then delete them when you quit the application. Crashes or system errors, however, may prevent an application from deleting these files. These files can build up over time, taking up disk space and causing problems. From time to time, you should quit all programs and remove all temporary files.

To delete temporary files:

1. Choose one of the following:

-- (Windows XP) Start > Search > All Files and Folders

-- (Windows 2000 or Me) Start > Search > For Files and Folders

-- (Windows NT or 98) Start > Find > Files or Folders

2. In the Named text box, *.tmp.

3. Choose Local Hard Drives from the Look In pop-up menu.

4. Click Find Now or Search Now.

5. When the search results appear, choose Edit > Select All.

6. Choose File > Delete. Click Yes to send the files to the Recycle Bin.

7. Empty the Recycle Bin.

The first time you delete temporary files, you should also make sure that adequate free space is available on the hard disk to which applications write temporary files. Quit all applications and then do one of the following:

-- In Windows Me or 98, edit the "Set Temp=" line in the Autoexec.bat file to specify a folder on an uncompressed hard disk that has sufficient free space:

1. Make a backup copy of the Autoexec.bat file.

2. Open the original Autoexec.bat file in a text-editing application that can save in text-only format (for example, Windows Write or Notepad.

3. Locate the line that begins:

Set temp=

The folder designated on the right of the equal sign is where Windows stores most of its temporary files.

4. Note the drive letter and folder name (for example, C:/Temp). If this line doesn't exist, you'll create it in step 7.

5. In Windows Explorer, verify that the drive and folder exist. If the drive doesn't exist, choose another drive. If the folder doesn't exist, create it by clicking the drive, then choosing File > New > Folder, then naming the folder Temp.

6. Make sure the drive has at least 20 MB of free space by right-clicking it, then choosing Properties from the pop-up menu and noting the Free Space field. If the drive doesn't have enough space, either remove unnecessary files from it or edit the line in the Autoexec.bat file to specify a drive that does have enough space.

7. In the Autoexec.bat file, if this line doesn't exist, add it using the following format:

Set temp=C:\Temp

where "C" is a drive with enough free space and "Temp" is the folder you verified or created.

8. Save the Autoexec.bat file in text-only format.

9. Restart Windows.

-- In Windows XP, 2000, or NT, edit or add the TEMP user variable in the System Control Panel to specify a folder on an uncompressed hard disk that has sufficient free space:

1. Do either of the following:

-- (Windows XP) Choose Start > Control Panel, double-click System, click the Advanced tab, and then select Environment Variables.

-- (Windows 2000) Choose Start > Settings > Control Panel, double-click System, click the Advanced tab, and then click Environment Variables.

-- (Windows NT) Choose Start > Settings > Control Panel, double-click System, and then click the Environment tab.

2. In the User Variables section, locate TEMP in the Variable column. The folder designated in the Value column is the folder where Windows stores most of its temporary files.

Note: This section may also list a TMP variable. Some applications use the TMP variable to determine where to write their temporary files, while others (including Photoshop) refer to the TEMP variable. Although you can assign different drives and folders to either variable, you'll have an easier time removing temporary files if Windows stores them in one place.

3. Note the drive letter and folder name, for example, C:/Temp, in the Value column. If the drive is designated as "%SystemDrive%," this is the drive on which the Winnt folder resides. If this value doesn't exist, you will create it in step 6.

4. In Windows Explorer, verify that the drive and folder exist. If the drive doesn't exist, choose another drive. If the folder doesn't exist, create it by selecting the drive, then choosing File > New > Folder and naming the folder Temp.

5. Check the amount of free space on the drive: Right-click it, choose Properties from the pop-up menu, and on the General tab, note the value in the Free Space field. If the drive has less than 20 MB of free space, either remove unnecessary files from it or edit the value of the TEMP variable to specify a drive that has enough free space.

Note: Check with your system administrator before editing or adding a variable; you may need to have administrator access.

6. If the TEMP variable doesn't exist in the User Variables section, type TEMP in the Variable text box. If the TEMP variable exists, select the variable name. Then, type the following in the Value text box:

C:\Temp

where "C" is a drive with enough free space and "Temp" is the folder you verified or created.

7. Click Set and then click OK.

8. Restart Windows.

Optimizing and defragmenting hard disks

Over time, the computer's hard disk can become damaged or fragmented (unavailable in a large contiguous block). If there is not enough contiguous space for the system to save a file, it saves pieces of the file to different locations on the disk. It takes an application longer to read a fragmented file whose pieces are saved in several locations.

To optimize and defragment the hard disk:

-- In Windows 2000 or XP, use the Disk Defragmenter: Choose Start > Programs > Accessories > System Tools > Disk Defragmenter (Windows 2000) or Start > All Programs > Accessories > System Tools > Disk Defragmenter (Windows XP).

-- In Windows 98 or Me, use the ScanDisk and Disk Defragmenting utilities included with Windows: Choose Start > Programs > Accessories > System Tools.

-- In Windows NT, use a third-party utility. (You can type CHKDSK/f at the command prompt, and press Enter to scan hard disks for errors.)

Windows virtual memory and Photoshop scratch disk files

Virtual memory allows your system to use hard-disk space to store information normally stored in memory (RAM). Because it takes longer to access information on a hard disk than it does to access information in memory, using a portion of the hard disk as virtual memory can decrease performance. In addition, Photoshop cannot use the hard-disk space the system uses for virtual memory for its scratch disk files, which it uses to store image information as you work. If you need more memory to work in Photoshop, Adobe Systems recommends installing more RAM.

Specifying a fixed virtual memory setting helps prevent Photoshop scratch disk files from competing for the same space with virtual memory, especially if you set the virtual memory setting on a different drive than the primary scratch disk. For both kinds of virtual memory, be sure to use a drive with enough free, uncompressed space. RAID 0 partitions provide the best possible performance as Photoshop scratch disks.

-- In Windows XP, 2000, or NT:

1. Quit all applications.

2. Choose Start > Settings > Control Panel, double-click System, and do one of the following:

(Windows XP or 2000) Click the Advanced tab, and then select Settings in the Performance section.

(Windows NT) Click the Performance tab.

3. In the Virtual Memory section, do one of the following:

(Windows XP) Click the Advanced tab, and in the Virtual memory section, click Change.

(Windows NT or 2000) Click Change.

4. From the Drive list, select a hard drive that has at least twice the amount of your computer's installed RAM, or for Windows XP, 1.5 times the amount of your computer's installed RAM. For example, if your computer has 256 MB of RAM, select a hard drive that has at least 512 MB of free hard drive space, or 384 MB for Windows XP. For best performance, choose a hard drive not used for the Photoshop scratch disk(s).

5. In the Paging File Size for Selected Drive section, select Custom size (Windows XP only), and in the Initial Size box, enter a value equal to the twice the amount of your computer's installed RAM.

6. In the Maximum Size box, enter a value equal to four times the amount of your computer's installed RAM.

7. Click Set and then click OK. Note: For the best performance, the Paging File should be on a separate, empty, de-fragmented hard disk.

8. Click to close the System Control Panel Applet (Windows XP) or the System dialog boxes (Windows NT or 2000).

9. To restart Windows, click Yes in the System Settings Change dialog box.

-- In Windows 98:

1. Quit all applications.

2. Create a Windows startup disk by choosing Start > Settings > Control Panel, double-clicking Add/Remove Programs, clicking the Startup Disk tab, then following the on-screen instructions. (After changing system settings, such as virtual memory, Windows may be unable to start, so you may need start from a startup disk.)

3. Choose Start > Settings > Control Panel; double-click System, then click the Performance tab and click Virtual Memory.

4. Select "Let Me Specify My Own Virtual Memory Settings."

5. From the Hard Disk pop-up menu, choose a hard drive that has at least twice the amount of your computer's installed RAM. For example, if your computer has 256 MB of RAM, choose a hard drive that has at least 512 MB of free space. (To check how much free space a drive has, start Windows Explorer, then right-click the drive and choose Properties from the pop-up menu and note the Free Space field.)

6. In both the Minimum and Maximum text boxes, enter a value equal to twice the amount of your computer's installed RAM.

7. Click OK to close the Virtual Memory dialog box.

8. Click Yes when you see the message, "You have chosen not to let Windows manage virtual memory automatically ..." in the Confirm Virtual Memory Setting dialog box.

9. Click Close in the System Properties dialog box.

10. Restart Windows by clicking Yes in the System Settings Change dialog box. If Windows doesn't restart, insert the startup disk and then restart Windows.

Applications running in the background

As it starts, Windows uses some of the installed RAM. Photoshop competes with other programs you start for the remainder. You may not be aware of programs that start automatically and run in the background. Make sure that no programs start automatically when Windows starts by doing the following:

-- Remove programs from the Startup folder:

1. Quit all applications.

2. Start Windows Explorer.

3 Move all icons and shortcuts from the following locations to another folder:

((Windows 2000) Documents and Settings/[user profile]/Start Menu/Programs/Startup and Documents and Settings/All Users/Start Menu/

(Windows Me) Windows/Start Menu/Programs/Startup folder and Windows/All Users/StartMenu/Programs/Startup

(Windows NT) Winnt/Profiles/[user profile]/Start Menu/Programs/Startup and Winnt/Profiles/All Users/Start Menu/Programs/Startup

(Windows 98) Windows/Start Menu/Programs/Startup folder

5. Restart Windows. You can move the icons and shortcuts back if performance doesn't improve noticeably.

To disable startup items:

1. Quit all applications.

2. Choose Start > Run, and type msconfig in the Open text box, and then Click OK.

3. Click the Startup tab, and select Disable All.

4. Deselect any startup items that are essential for testing the problem. (For example, Acrotray.exe is required for making Adobe PDF files with Acrobat). If you are unsure if an item is essential, leave it selected.

5. Click OK, and then restart Windows.

6. Right-click to close or disable any items in the Notification Area (called the System Tray in earlier versions of Windows).

Then, try to re-create the problem:

-- If the problem doesn't occur, one of the Startup items conflicts with Acrobat. Re-enable the Startup items one at a time until you determine which item conflicts with Acrobat. Then, contact the developer of that item to see if an update is available.

-- If the problem recurs, Startup items aren't the cause and you can re-enable them:

a. Choose Start > Run, and type msconfig in the Open text box. Click OK.

b. Click the Startup tab, and select Enable All.

c. Click OK, and restart Windows.

-- Quit active applications one by one (except Explorer and Systray, fundamental Windows components): Press Ctrl+Alt+Delete, select an application in the Close Program dialog box, and then click End Task.

-- Close applications that are specified to start automatically in the registry:

1. Restart Windows.

2. Right-click on the task bar.

3. Choose Task Manager from the pop-up menu.

4. Click the Applications tab.

5. Select an application name, then click End Task.

6. Restart Photoshop. If performance improves noticeably, contact the application's manufacturer for help in permanently disabling it from starting automatically.

Hardware

Photoshop performance is limited by the hardware you use: the faster the processor or hard disk you use, the faster Photoshop can process image information. Other hardware options, such as installing additional RAM, using a multiprocessor system, or using optimized and defragmented disks, can also improve performance.

Processor speed

Speed is limited by the speed of the computer's processor, or CPU (Central Processing Unit). Since Photoshop manipulates large quantities of data and performs many calculations, its speed is greatly dependent on the processor's speed. Photoshop requires a Pentium III or 4 processor. Photoshop CS has not been tested with the Intel Itanium chip, and does not take advantage of its 64-bit processing.

All Photoshop features are faster on a multiprocessor system, although some can take greater advantage of the multiprocessor system's capabilities.

Installed RAM

To work with an image, Photoshop requires at least three to five times the file size of the image in available memory (RAM). If Photoshop has insufficient memory, it uses hard-disk space (scratch disk) to process information. Because accessing information in memory is faster than accessing information on a hard disk, Photoshop is fastest when it can process all or most image information in memory (RAM), without using the scratch disk. Allocate enough memory to Photoshop to accommodate your largest image file.

To check use of memory for Photoshop, open the Efficiency Indicator:

1. Click the triangle in the bottom border of the application window.

2. Choose Efficiency to display the percentage of time actually doing an operation instead of reading or writing the scratch disk. If the value is less than 100%, Photoshop is using the scratch disk and, therefore, is operating more slowly.

Hard disks

Since Photoshop reads and writes image information while working on an image, the faster the access speed of the disk containing your image or the scratch disk, the faster Photoshop can process image information. To improve Photoshop performance, work on files saved on disks with fast access speeds, such as an internal hard disk, rather than those with slow access speeds, such as a network server (hard disk accessed over a network) or removable media, for example, Zip disks. Removable media often have slower access times and are more easily damaged than nonremovable disks.

Resources

The following books and Web sites provide troubleshooting tips and general information about Windows.

Books

Microsoft Windows Resource Kits

Windows for Dummies books

Peter Norton's Complete Guide to NT 4 Workstation

Web sites

Microsoft Support: support.microsoft.com

BYTE Magazine: www.byte.com

CNET: www.cnet.com

EWeek: www.eweek.com
John Savill's Windows NT/2000: www.ntfaq.com

PC World: www.pcworld.com