Windows Optimizing Blog

The performance of Adobe Photoshop CS2 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 CS2 supports new maximum image dimensions, and file sizes requiring increased system requirements. The maximum file size Photoshop CS2 supports is 300,000 x 300,000 pixels, except for PDF files, which are still constrained by the 30,000 x 30,000 pixel limitation.

Photoshop CS2 has an increased file size capability for the following file types:

-- PSD files: 2 GB

-- TIFF files: 4 GB

Note: Most applications cannot work with TIFF files over 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).

Note: Large Document Format files (.PSB) 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.

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 650 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 CS2 supports up to 64 exabytes (EB) of scratch disk space on a total of four volumes. (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.

6. Restart Photoshop.

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 6. 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. If you have performance issues in Photoshop CS2, set the Image Cache to 2, then test your performance.

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

To adjust the Image Cache setting:

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

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

3. Restart Photoshop.

Set Maximize PSD And PSB File Compatibility to Ask

Maximize PSD and PSB File Compatibility increases the size of your file by attaching a flattened copy of your image when you save your image. In past versions of Photoshop, you didn't need to keep this option on. In Photoshop CS2, however, a small amount of extra data is included in the file when you choose this option that ensures that PSD and PBS files saved in Photoshop CS2 will open in previous versions. Additionally, when this option is on, and you open a Photoshop CS2 image in a previous version with a feature in it that cannot be supported by the older version, Photoshop will display a warning message.

If you are saving files in Photoshop CS2 for use in older versions, then save them with this option on (that is, set to Ask or Always).

To change the Maximize File Compatibility option:

1. Choose Photoshop > Preferences > File Handling.

2. Change Maximize PSD And PSB File Compatibility to one of the following:

-- Ask: Prompts you to maximize file compatibility when you save.

-- Always: Saves with maximized file compatibility without asking.

-- Never: Does not save or prompt you to save with maximized file compatibility.

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 Extract command

When you run the Extract command (Filter > 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.

16-bit functionality

Photoshop CS2 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.

Adjusted Refresh plug-in

This plug-in is not necessary for Photoshop CS2, because the new maximum tile size in Photoshop CS2 is 132 KB. The amount of space set aside for and displayed in the Scratch Sizes indicator in Photoshop CS was much larger than in earlier versions because the tile sizes were larger. The Adjusted Refresh plug-in reduced the initial scratch disk usage when you started Photoshop, and reduced the size of the Photoshop image tiles from the default size of 1 MB per tile to 64 KB per tile. The smaller tiles allow the display to redraw in smaller pieces, reducing the time needed to preview some filter updates.

Bigger Tiles plug-in

The Bigger Tiles plug-in, which is located in the Program Files\Adobe\Adobe Photoshop CS2\Plug-Ins\Adobe Photoshop Only\Extensions\Bigger Tiles folder, is disabled by default. When you enable it by removing the ~ from the filename, then you increase the image tile size in Photoshop. You should only enable the plug-in if you have more than 1 GB of RAM installed.

If you enable the plug-in, then Photoshop redraws more data at a time because each tile is larger, and each tile is drawn, complete, at one time. Photoshop takes less time to redraw fewer tiles that are larger, than more tiles that are smaller. Because Photoshop redraws more data at one time, each tile it takes longer to be redrawn; so bigger tiles can look like they are redrawing slower, but they are actually redrawing faster than if the image had more smaller tiles.

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:

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.
Part 2