Optimize performance | Photoshop CS4, CS5, CS6

There are four primary ways to affect performance in Photoshop:

• optimize your hardware setup
• specify Performance preferences
• use good work habits in Photoshop
• take certain steps to speed your OS

For best results, however, take a holistic approach to optimizing Photoshop performance. Read all of the suggestions here. Consider which ones to implement within the context of your computer setup, the types of files you use, and your particular workflow. Each circumstance is unique and requires a different combination of techniques to get the most efficient performance from Photoshop.

• Use a fast enough processor
• Max out on RAM
• Use a fast, large hard disk
• Solid-state disks

The speed of the computer’s central processing unit, or CPU, limits the processing speed of Photoshop. Photoshop CS4 requires a PowerPC G5 or multicore Intel processor (Mac OS) or a 1.8 GHz or faster processor (Windows). Photoshop CS5 and CS6 require a multicore Intel processor (Mac OS) or a 2 GHz or faster processor (Windows).

Photoshop generally runs faster with more processor cores, although some features take greater advantage of the additional cores than others. There is a law of diminishing returns with multiple processor cores: The more cores you use, the less you get from each additional core. Therefore, Photoshop doesn’t run four times as fast on a computer with 16 processor cores as on a computer with four cores. For most users, the increase in performance that more than six cores provides doesn't justify the increased cost.

Photoshop CS6 also employs the Graphics processor (GPU) more than previous versions to enhance the performance of more features. This increase in GPU use can cause performance issues when running Photoshop CS6 in a virtual environment. Virtual machines cannot access the GPU.

Photoshop uses random access memory (RAM) to process images. If Photoshop has insufficient memory, it uses hard-disk space, also known as a scratch disk, to process information. Accessing information in memory is faster than accessing information on a hard disk. Therefore, Photoshop is fastest when it can process all or most image information in RAM. If possible, allocate enough RAM to Photoshop to accommodate your largest image file.

How much RAM can Photoshop access?

* 64-bit Photoshop is not officially supported on 64-bit Windows XP, but it should run.

For more information on performance and 64-bit Photoshop, see 64-bit operating system benefits and limitations | Photoshop CS4, CS5.

For instructions on allocating RAM to Photoshop, see Memory Usage.

Photoshop reads and writes image information to disk when there is not enough RAM to contain all of it. Check the efficiency indicator as described below to determine whether getting a faster hard disk or solid-state disk would improve your performance. If the efficiency number is above about 95%, spending money on a faster scratch disk has little benefit.

To improve Photoshop performance, use a disk with a fast data transfer rate. For example, use an internal hard disk or an external disk connected via a fast interface such as Thunderbolt, FireWire 800, eSATA, or USB3. Network servers (hard disk accessed over a network) have slower data transfer rates.

Photoshop requires at least 1 GB of free hard-disk space (Windows) or 2 GB of free hard-disk space (Mac OS). Installation requires additional space, and Adobe recommends more hard-disk space for virtual memory and scratch disk space.

Fast RAID 0 arrays make excellent scratch disks, especially if the array is used exclusively for your scratch disk. Also make sure that the array is defragmented regularly, and isn't your startup volume. 

Installing Photoshop on a solid-state disk (SSD) allows Photoshop to launch fast, probably in less than a second. But that speedier startup is the only time savings you experience. That’s the only time when much data is read from the SSD.

To gain the greatest benefit from an SSD, use it as the scratch disk. Using it as a scratch disk gives you significant performance improvements if you have images that don’t fit entirely in RAM. For example, swapping tiles between RAM and an SSD is much faster than swapping between RAM and a hard disk.

If your SSD doesn’t have much free space (the scratch file grows bigger than can fit on the SSD), add a secondary or tertiary hard disk. (Add it after the SSD.) Make sure that these disks are selected as scratch disks in the Performance pane of Preferences.

Also, SSDs vary widely in performance, much more so than hard disks. Using an earlier, slower drive results in little improvement over a hard disk.

Note: Adding RAM to improve performance is more cost effective than purchasing an SSD. If money is no object, you're maxed out on installed RAM for your computer, you run Photoshop CS5 as a 64-bit application, and you still want to improve performance, consider using a solid-state disk as your scratch disk.

As noted above, an SSD doesn't improve performance if the efficiency indicator is already high. The lower the efficiency indicator, the greater the improvement an SSD offers.

The Performance preferences you specify greatly affect Photoshop performance. To set Performance preferences, choose Photoshop > Preferences > Performance (Mac OS) or Edit > Preferences > Performance (Windows). Then, specify options in each of the following areas:

• Memory Usage
• Scratch Disks
• History & Cache preferences
• GPU Settings

The more RAM available to Photoshop, the faster Photoshop can process image information. The Memory Usage area of the Performance preferences dialog box tells you how much RAM is available to Photoshop. It also shows you an ideal range for your system.

Note: Available RAM is not your total RAM. Photoshop subtracts RAM required for the operating system. 

By default, Photoshop uses 70% of available RAM. You can assign more or less RAM to Photoshop by changing the value in the Let Photoshop Use box. Or, you can drag the Memory Usage slider. Restart Photoshop for changes to take effect.

The default RAM allocation of 70% is fine for most people running the 32-bit version of Photoshop. To find the ideal RAM allocation for your system, change it in 5% increments and monitor performance in the Efficiency status indicator. See Keep an eye on the Efficiency indicator.

If you run the 64-bit version of Photoshop and you experience out-of-RAM or out-of-memory errors, increase your RAM allocation. With no other applications running, you can increase the RAM allocation to 100% to improve Photoshop performance.

If you run the 32-bit version of Photoshop, you can experience out-of-RAM errors if you set the RAM allocation to 100%. If you get out-of-RAM errors, reduce the RAM allocation to 85% to 90% and retest. If problems continue, reduce the RAM allocation in 5% increments. Retest until the error stops occurring, or use the 64-bit version of Photoshop if you can.

Set the scratch disk to a defragmented hard disk that has plenty of unused space and fast read/write speeds (see Defragment the hard disk). If you have more than one hard drive, you can specify additional scratch disks. Photoshop supports up to 64 exabytes of scratch disk space on up to four volumes. (An exabyte equals 1 billion GB.)

If your startup disk is a hard disk (as opposed to a solid-state disk), try using a different hard disk for your primary scratch disk. If your startup disk is an SSD, there is no benefit to selecting a different disk for your primary scratch disk. Using the SSD for both your system startup disk and your primary scratch volume performs well. And, it's probably better than using a separate hard disk for scratch. See Assigning scratch disks in Photoshop Help for more information.

Photoshop uses image caching to speed redrawing of high-resolution images. With caching, Photoshop uses low-resolution versions of images to quickly update the image onscreen. The Cache Levels option allows you to tell Photoshop to save one through eight levels of cached image data. The more cache levels you have, the slower Photoshop opens the file, but the more responsive it is while you work. The fewer cache levels you have, the faster the image loads, but the slower Photoshop performs. 

The default Cache Levels setting is 4. However, you can change that depending on the types of files you work with and how much RAM you have.

If you use relatively small files—roughly 1 megapixel or 1280 by 1024 pixels—and many (50+) layers, set the cache to 1 or 2. Setting Cache Levels to 1 disables image caching; only the current screen image is cached.

Note: Some features in Photoshop don't produce the highest-quality result if Cache Levels is 1.

If you use files with larger pixel dimensions—say, 50 megapixels or larger—set Cache Levels higher than 4. Setting a higher cache level improves performance by speeding redraw times.

The cache tile size is the amount of data (tiles) that Photoshop operates on at one time. Photoshop processes each tile of data, then redraws it. Photoshop is more efficient when it operates on larger tiles, but larger tile sizes take longer to redraw. Bigger tiles make complex operations such as sharpening filters go faster. However, smaller changes such as brush strokes are more responsive when Photoshop uses smaller tiles. 

In Photoshop CS4, you can change the cache tile size using the Bigger Tiles optional plug-in (see Bigger Tiles plug-in (Photoshop CS4).

In Photoshop CS5 and CS6, you can choose a tile size from the Cache Tile Size pop-up menu in Performance preferences. If you have an Intel "Core" processor, choose 128 K or 1024 K. If your processor is an Intel Pentium 4 or AMD, Photoshop is more efficient using 132 K or 1032 K.

In Photoshop CS5 and CS6, the History & Cache section of the Performance preferences also has three cache presets: Tall And Thin, Default, and Big And Flat. These options set your cache level and tile size based on the kind of document you’re editing and the amount of RAM you have.

• Tall And Thin Better for editing images with smaller pixel dimensions that have many layers (dozens to hundreds).
  
• Big And Flat Better for editing images with larger pixel dimensions (many tens to hundreds of megabytes) and fewer layers.
  
• Default For images in between.

Each history state, or snapshot, of an operation that affects the entire image increases the amount of scratch disk space that the file requires. Photoshop creates a copy of the original. So, for example, if you apply a Gaussian blur to a 500-KB image and create a snapshot of that edit in the History panel, Photoshop requires 1 MB of scratch disk space for the image. If you apply a Levels adjustment, a Noise filter, and an unsharp mask to a 5-MB image and save a History snapshot of each state, the image requires 15 MB of scratch disk space.

Each history state or snapshot in the History panel increases the amount of scratch disk space that Photoshop uses.  The more pixels an operation changes, the more scratch space the corresponding history state consumes. A history state corresponding to a small paint stroke or a non-destructive operation such as creating or modifying an adjustment layer consumes little scratch space. A history state corresponding to applying a filter to the entire image consumes much more scratch space.

You can save scratch disk space and improve performance by limiting or reducing the number of states that Photoshop can save in the History panel. Photoshop can save up to 1,000 history states; by default, it allows you to save 20. To reduce that number, click the History States pop-up menu in the History & Cache area of the Performance preferences dialog box, and drag to a lower value.

The Bigger Tiles plug-in, which is located in the Optional Plug-ins folder on the application DVD, is disabled by default. To enable it, copy it to the Extensions folder in your Photoshop CS4 Plug-ins folder and remove the tilde (~) from the filename. Only enable the plug-in if you have more than 1 GB of RAM installed.

When you enable the plug-in, it increases the image tile size in Photoshop. Photoshop redraws more data at a time because each tile is larger, and each tile is drawn, complete, at one time. It takes less time to redraw fewer tiles that are larger than it takes to redraw more tiles that are smaller. Bigger tiles sometimes seem to redraw more slowly. In fact, it can take longer to see the results onscreen if you’re making repeated small adjustments. However, the total time it takes to compute and draw the final image is less. Screen updates while painting can be less smooth with Bigger Tiles installed.

If you spend most of your time painting or rapidly tweaking controls in filters or panels and Photoshop redraw is responsive, then don’t enable Bigger Tiles. But if you spend your time watching progress bars crawl across the screen, enable Bigger Tiles to improve performance.

Photoshop CS4 and CS5 leverage the GPU on your computer’s video adapter to speed screen redraw operations. For Photoshop to access the GPU, the video adapter must have a GPU that supports OpenGL. It also requires at least 128 MB of RAM, and a driver that supports OpenGL 2.0 and Shader Model 3.0.

The best way to optimize GPU acceleration is to make sure that you keep your video adapter driver up to date. For more information about GPU acceleration and instructions on updating video adapter drivers, see Photoshop CS6 GPU FAQ or GPU and Open GL support | Photoshop CS4, CS5. For instructions on specifying GPU Settings in the Performance preferences dialog box, see Photoshop CS6 GPU FAQ or GPU and Open GL features and preferences | Photoshop and Bridge | CS4, CS5.

The Save In Background preference is on by default. When it is on, Photoshop lets you continue working while Save and Save As commands are performed instead of requiring you to wait until they complete. If you want to see the progress of a background save operation, you can select Save Progress in the Status pop-up menu. Save operations performed in the background (that is, with the preference on) take longer. However, you don’t have to wait on them to complete to keep working.

In most cases, background save operations do not significantly affect the performance or responsiveness of normal Photoshop operations. However, if you are editing a file that is much larger than available RAM, the save operation can affect responsiveness or performance until the save is complete.

The Automatically Save Recovery Information Every preference is enabled only if Save in Background is on. If enabled, recovery information is saved for each open file at the specified interval. This recovery information is saved in the background to a hidden location. Your original file is never modified. Your original file is only modified in response to your explicit Save or Save As commands. If Photoshop or the system crashes, the recovered information opens the next time you launch Photoshop.

Setting a lower value for the recovery interval gives more protection against crashes. In most cases, saving the recovery information does not affect the performance or responsiveness of Photoshop. However, depending on the operations you’re doing, and the size and number of open files, there can be some impact on performance.  This issue is most likely if the files you’re modifying on are larger than the available RAM.

Possible issues:

If Photoshop seems to intermittently slow down, select Save Progress in the status pop-up menu on the lower left of your image window. If you notice performance issues while the save progress bar is moving, increase the value of the Automatically Save Recovery Information Every preference. Or, turn off the preference.

Recovery information is saved in the same locations as the Photoshop scratch files. It increases the amount of space Photoshop uses on the scratch disks specified in the Scratch Disks preference in the Performance panel of Preferences. If you regularly keep many large files open while working, the amount of space can be significant. If you get out of disk space errors while performing commands other than Save commands, add scratch disk space. Or, disable the Automatically Save Recovery Information preference.

• Work within file-size limitations
• Keep an eye on the Efficiency indicator
• Close unnecessary document windows 
• Reduce patterns and brush tips in presets
• Minimize or turn off panel preview thumbnails
• Set Maximize PSD And PSB File Compatibility to Ask
• Work in 8-bit image mode
• Turn off WYSIWYG font preview
• Reduce image resolution
• Purge Undo, the Clipboard, and History states
• Use the Filter Gallery
• Drag between files
  
• Use layers wisely
• Save TIFF files without layers
• Don’t export the Clipboard

The larger the file you’re working with, the more likely it is that you encounter performance problems. 

Photoshop supports a maximum file size of 300,000 x 300,000 pixels, except for PDF files, which are limited to 30,000 x 30,000 pixels and 200 x 200 inches.

File size capability for Photoshop:

• PSD files: 2 GB
• TIFF files: 4 GB (Photoshop CS6 supports TIFF files over 4 GB)
  

Note: Most applications cannot work with TIFF files larger than 2 GB.

• PSB files: 4 exabytes (4096 petabytes or 4 million terabytes)
• PDF files: 10 GB (pages are limited to a maximum size of 200 inches)

See also File size in Photoshop CS5 Help.

Photoshop CS6 supports odd bit-depths in addition to even bit-depths.

Watch the Efficiency indicator while you work in Photoshop. It tells you when Photoshop has used all available RAM and starts using the scratch disk, which slows performance. Click the pop-up menu at the bottom of the image window and choose Efficiency. (You can also view the Efficiency status in the Info panel. See Work with the Info panel in Photoshop CS5 Help.) If the Efficiency value is below 100%, Photoshop is using the scratch disk and. Therefore, it is operating more slowly. If the efficiency is less than 90% to 95%, allocate more RAM to Photoshop in Performance preferences (see Memory Usage). Or, add additional RAM to your system.

Document windows use more RAM in Photoshop CS4, CS5, and CS6 than in previous versions. Too many open images in Photoshop can result in an “out of RAM” error message or cause Photoshop to run slowly. If this error occurs, close some document windows.

To reduce the amount of scratch space Photoshop uses, minimize the number of patterns and brush tips you keep loaded. Save presets you don’t require right now to a preset file. Or delete them if they were loaded from a preset file.

To view the loaded pattern or brush presets, choose Edit > Preset Manager. Then, choose Preset Type > Patterns or Preset Type > Brushes. To save pattern or brush presets you aren’t using, select them in the Preset Manager. Then, click Save Set and specify a filename for them. Click the Delete button to delete them from the loaded presets. If you need them later, you can reload them from within the Preset Manager or the various pop-up menus for patterns and brushes.

Each time you change the document, Photoshop updates all the thumbnails visible in the Layers and Channels panels. This update can affect responsiveness when rapidly painting, moving, or nudging layers. The more thumbnails are visible, the greater this effect.

To minimize or disable thumbnail previews in these panels, click Channels, Layers, or Paths panel and choose Panel Options. In the Thumbnail Size area, select a smaller thumbnail size or choose None, and then click OK.

The Maximize PSD And PSB File Compatibility feature attaches a flattened copy of the image when you save it. This extra data ensures that PSD and PSB files can be opened in previous versions of Photoshop, in Photoshop Lightroom, and in non-Adobe applications that support PSD files. It also permits QuickLook previews in the Finder and Open dialogs on Mac OS. For large, layered files with only a few layers the increase in size can be significant. Saving the compatibility information also takes longer for large documents.

To make saving documents faster at the expense of more disk space:

See Maximize compatibility when saving files in Photoshop CS5 Help for more information.

Photoshop can perform many operations on 16-bit and 32-bit images. However, these images require more memory, scratch space, and time to process than 8-bit images. To convert your image to 8 bits per channel, choose Image > Mode > 8 Bits/Channel. See Bit Depth in Photoshop CS5 Help for more information.

Note: Converting to 8 bpc deletes data from your image. Save a copy of the original 16-bit or 32-bit image before you convert to 8 bpc.

Camera Raw can open images with either 8 bits or 16 bits per channel. To change this setting, open the Camera Raw dialog by opening a raw file. Click the underlined blue text below the preview image, and select 8 Bits/Channel  or 16 Bits/Channel from the Depth pop-up menu.

Turning off the WYSIWYG font preview list speeds the processing of fonts in Photoshop. In Photoshop CS4 and CS5, choose Photoshop > Preferences > Type (Mac OS) or Edit > Preferences > Type (Windows). Deselect Font Preview Size and click OK. In Photoshop CS6, choose Type > Font Preview Size > None.

See Troubleshoot fonts | Photoshop CS5 for more assistance with fonts.

The greater the resolution, the more memory and disk space Photoshop requires to display, process, and print an image. Higher image resolution does not necessarily provide higher image quality. But it can mean slower performance in Photoshop, use of additional scratch disk space, and slower printing. The optimal resolution for your images depends on how the images are displayed or printed. It is often useful to do most processing of your image at its original resolution. Then, when you begin optimizing the image for a particular output medium, reduce the image size and resolution to something suitable for that medium. (Save a copy of your full resolution original.)

For images presented on screen or in email, think in terms of total pixel dimensions. Many web images are no more than 700 pixels wide. Displays are getting larger all the time, but the largest ones in common use today are 2560 X 1600 pixels, or about four megapixels.

To reduce the image dimensions of an image in Photoshop, choose Image > Image Size. In the Image Size dialog box, make sure that both the Constrain Proportions and Resample Image boxes are selected. Enter a new value for the Pixel Dimensions Width or Height. (Entering a value for one changes both because the Constrain Proportions option fixes their relationship.)

For printed images, increasing resolution beyond about 360 DPI brings marginal if any benefits in most cases. If you produce many prints, it is worth experimenting to find a resolution that gives you pleasing results.

To reduce the resolution of an image in Photoshop, choose Image > Image Size. In the Image Size dialog box, select Resample Image. Change the Document Size values to reflect the physical size at which you plan to print the document. Then, decrease the Resolution value, and click OK. If the resolution value is lower than the value you had in mind, rather than higher (in other words, if you would be increasing the resolution of the document rather than decreasing it) see other documentation on printing images for how to best print low-resolution images.

If you are going to increase the image resolution for printing rather than decrease it, perform this resolution increase as one of your last steps before printing the image. That way, you don’t have to process all this extra information in earlier steps.

For more information, see Advanced cropping, resizing, and resampling | Photoshop, as well as Preparing to print from Photoshop and What's new and how to print in Photoshop.

Undo, the Clipboard, and History states all hold image data. To free up RAM, choose Edit > Purge and then Undo, Clipboard, Histories, or All. 

Note: The Purge command cannot be undone.

The contents of the clipboard are often large if you’ve been copying and pasting data within large documents. And, they’re of little use when you’re done pasting. The Undo and History states, however, often contain useful data for correcting previous mistakes. Purging history and undo make more RAM available immediately. However, those unused history states are automatically moved from RAM to scratch disk anyway as you work. So purging history and undo is only useful in limited circumstances.

The Filter Gallery allows you to test one or more filters on an image before applying the effects, which can save considerable time. See Filter Gallery overview in Photoshop CS5 Help for more information.

Dragging 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.

Layers are fundamental to working in Photoshop, but they increase file size and redraw time. Photoshop recomposes each layer after each change in the image. After you have completed changes to layers, flatten (merge) them to reduce the size of a file. Select the layers in the Layers panel, right-click (Windows) or Control-click (Mac OS) and choose Merge Layers. (Make sure to remove empty layers from the file since they bloat its file size. Select the empty layers in the Layers panel, right-click [Windows] or Control-click [Mac OS] and choose Delete Layer.) To flatten all layers in a file, choose Layer > Flatten Image.

Note: Photoshop does not let you separate layers after merging them. You can either choose Edit > Undo or use the History panel to return to an unmerged state.

If you don't frequently change some of your layers, consider converting layers or layer sets into Smart Objects, which saves disk space and improves performance. Select the layers or layer sets in the Layers panel, right-click (Windows) or Control-click (Mac OS) and choose Convert To Smart Object.

Photoshop can save layers in TIFF files. However, layered TIFF files are larger than flat 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, choose File > Save As. In the Save As dialog box, choose Format > TIFF, select Save As A Copy, deselect Layers, and click Save.

For added speed when exporting TIFF files, do not choose ZIP compression. ZIP compression produces the smallest TIFF files, however.

The Export Clipboard setting causes Photoshop to make the contents of the clipboard available to other programs. If you copy large amounts of data in Photoshop, but won't paste it into other applications, save time by turning off the Export Clipboard option.

• Close unnecessary applications and start up items
• Run Disk Cleanup (Windows)
• Defragment the hard disk
• Install current OS updates
• Specify a fixed virtual memory (Windows)

Other open applications and startup items decrease the amount of memory available to Photoshop. Quit unnecessary applications, startup items, and extensions. Then, make more memory available to Photoshop. See the following topics in the Adobe OS troubleshooting support documents:

• Run or reinstall the Adobe application while no other applications are running (Windows) 
• Disable extensions using Extension Manager (Windows)
• Run the application while no other applications are running (Mac OS)
• Run the Adobe application with login items disabled (Mac OS)
• Disable extensions using Extension Manager (Mac OS)

 Then, see Memory Usage for instructions on allocating more RAM to Photoshop.

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, can prevent an application from deleting these files, causing them to take up disk space and create problems. From time to time, run Disk Cleanup to remove temporary files and any other files that are not being used.

As you add, delete, and move files on a hard disk, its available space is no longer a single, contiguous block. If the system does not have enough contiguous space, it saves fragments of files to different locations on the hard drive. It takes Photoshop longer to read or write a fragmented file than one saved to a contiguous location.

For instructions on defragmenting hard disks on Windows, see these Microsoft Help topics:

• (Windows XP) “Maintenance tasks that improve performance.” Follow instructions under “Step 4. Defragment your hard disk drive.”
• (Windows Vista) ” Improve performance by defragmenting your hard disk”

On Mac OS, use a disk utility such as Disk Defragmenter, Symantec Norton Utilities, or Micromat Drive 10. Fragmentation is rarely a problem on Mac OS, unless you normally run with the drive nearly full. For more information, see Defragment the hard disk and check for errors.

Note: RAID arrays don’t become fragmented. Fragmentation is more likely to be an issue if you use a single disk for everything. It can also be an issue if permanent files and the Photoshop scratch disk share a volume, especially if there’s not much free space. In this case, defragmenting the disk can make a significant difference.

Solid-state disks don’t need to be defragmented, because their performance doesn’t degrade significantly with normal levels of fragmentation.

Updates to the Windows or Mac OS X operating system improve its performance and compatibility with applications. 

Get Windows service packs and other updates from the Microsoft website. For assistance installing service packs and other updates, contact Microsoft technical support.

To get Mac OS X updates, choose Software Update from the Apple menu. For assistance installing updates, contact Apple technical support.

Important: Before you install a system update, check the system requirements for the Adobe software to ensure compatibility. (Also check any third-party software or hardware you use with the Adobe software.) If the update isn’t listed, contact Adobe or the manufacturer of your third-party software or hardware.

Virtual memory allows your system to use hard-disk space to store information normally stored in memory. It takes longer to access information on a hard disk than it does to access information in memory. Therefore, using a portion of the hard disk as virtual memory can decrease performance. Also, Photoshop cannot use the hard-disk space the system uses for virtual memory for its scratch disk files. (It uses the scratch disk to store image information as you work.)

Specifying a fixed virtual memory setting helps prevent Photoshop scratch disk files from competing for the space with virtual memory. Especially if you set the virtual memory setting on a different drive from the primary scratch disk. For both kinds of virtual memory, be sure to use a drive with enough free, contiguous space and for the best performance. Also, keep the Paging File on a separate, empty, defragmented hard disk.

As always, the advice to use separate disks for virtual memory and scratch disks does not apply to solid-state disks. With an SSD, it’s beneficial to put all the most heavily used files on an SSD. Putting them on the same SSD carries little or no penalty.

To change Virtual Memory in Windows XP, quit all applications and then do the following:

To change Virtual Memory in Windows 7 and Vista, quit all applications and then do the following:

For more information, see these Microsoft Help topics:

• (Windows XP) “To change the size of the virtual memory paging file”
• (Windows Vista and Windows 7) “Change the size of virtual memory”

Also see Virtual Memory, an excerpt from Real World Photoshop CS5 for Photographers (Peachpit Press), by Conrad Chavez.