Windows Optimizing Blog

Welcome Back...Now is the Part 2 or Back to Part 1

Purge Undo, Clipboard, or Histories

Undo, Clipboard, and Histories all hold image data. To release RAM, choose Edit > Purge to purge the Undo and Clipboard. Purging Histories can release RAM or scratch disk depending on how recent your history data is. To reduce disk space usage, reduce the number of History States available in the General preference.

Reduce the number of History states

In Photoshop CS2, each history state that includes an operation that affects the entire image (for example, when you apply Gaussian blur or unsharp mask to the entire image) creates a full copy of your image at its original size. If your initial image is 500 KB, and you apply Gaussian blur to it, your image will need 1 MB of scratch space. If your history states consist of operations that affect only part of the image, such as paint strokes, only the size of the tiles touched by the strokes are added to the image size. If you count up the number of histories you have where operations have affected the entire image, and multiply your original image size by that number, you'll have an approximate amount of scratch disk space the image will need. If you have applied levels, a reduce noise filter, and an unsharp mask filter to your entire image that's 5 MB in size, the image will need 20 MB of scratch space. When you reduce the number of history states available, you potentially reduce the number of copies of your image using scratch space.

Reduce patterns and brush tips

If you need to reduce your scratch disk overhead to a minimum, you can minimize the number of patterns and brush tips you use in each of your presets, and you can reduce the number of patterns you use in your image's Layer Styles (as applied with the Bevel and Emboss Texture or in the Pattern Overlay). Each small pattern and sampled brush in the presets uses at least one tile for storage. Patterns used in Layer Styles take extra RAM, as well.

Minimizing the number of layers

Layers are fundamental to working in Photoshop, but they also increase file sizes and redraw time because Photoshop recomposes each layer 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.

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.

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 Filter Gallery in Photoshop CS2 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 CS2 can only operate on computers running Windows 2000 or Windows XP.

Allocating more memory to Photoshop with 32-bit operating systems and computers

Photoshop uses random-access memory (RAM) to process image information. The more RAM available to Photoshop, the faster Photoshop can process image information. Other open applications and startup programs decrease the amount of memory potentially available to Photoshop. Quitting applications or startup items you are not using makes more memory available to Photoshop.

To allocate more memory to Photoshop:

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

2. In the Memory Usage section, increase the Maximum Used by Photoshop percentage, and click OK.

3. Restart Photoshop.

Allocating memory above 2 GB with 64-bit processors

Photoshop CS2 is a 32-bit application. When it runs on a 32-bit operating system, such as Windows 2000 and Windows XP Professional, it can access the first 2 GB of RAM on the computer.The operating system uses some of this RAM, so the Photoshop Memory Usage preference displays only a maximum of 1.6 or 1.7 GB of total available RAM. If you are running Windows XP Professional with Service Pack 2, you can set the 3 GB switch in the boot.ini file, which allows Photoshop to use up to 3 GB of RAM.

Important: The 3 GB switch is a Microsoft switch and may not work with all computers. Contact Microsoft for instructions before you set the 3 GB switch, and for troubleshooting the switch. You can search on the Microsoft support page for 3gb for information on this switch.

When you run Photoshop CS2 on a computer with a 64-bit processor (such as a, Intel Xeon processor with EM64T, AMD Athlon 64, or Opteron processor), and running a 64-bit version of the operating system (Windows XP Professional x64 Edition), that has 4 GB or more of RAM, Photoshop will use 3 GB for it's image data. You can see the actual amount of RAM Photoshop can use in the Maximum Used By Photoshop number when you set the Maximum Used by Photoshop slider in the Memory & Image Cache preference to 100%. The RAM above the 100% used by Photoshop, which is from approximately 3 GB to 3.7 GB, can be used directly by Photoshop plug-ins (some plug-ins need large chunks of contiguous RAM), filters, actions, etc. If you have more than 4 GB (to 6 GB), the RAM above 4 GB is used by the operating system as a cache for the Photoshop scratch disk data. Data that previously was written directly to the hard disk by Photoshop, is now cached in this high RAM before being written to the hard disk by the operating system. If you are working with files large enough to take advantage of these extra 2 GB of RAM, the RAM cache can speed performance of Photoshop.

The default RAM allocation setting is 55%. This setting should be optimal for most users. To get the ideal RAM allocation setting for your system, change the RAM allocation in 5% increments and watch the performance of Photoshop in the Performance Monitor. You must quit and restart Photoshop after each change to see the change take effect.

The available RAM shown in the Memory & Image Cache preferences already deducted an amount that is reserved for the OS at any given time from the total RAM in your machine. You shouldn't set the percentage of RAM to be used by Photoshop to 100%, because other applications which run at the same time as Photoshop (for example, Adobe Bridge) need a share of the available RAM. Some applications take use more RAM than you might expect. For example, web browsers can use 20-30 MB of RAM, and music players can use 20-50 MB RAM. Watch the Performance Monitor to view the RAM allocations on your computer.

Watch your efficiency indicator while you work in Photoshop to determine the amount of RAM you'll need to keep your images in RAM. The efficiency indicator is available from the pop-up menu (choose Show > Efficiency) on the status bar of your image and from the Palette Options on the Info Palette pop-up menu. When the efficiency indicator goes below 95-100%, you are using the scratch disk. If the efficiency is around 60%, you'll see a large performance increase by changing your RAM allocation or adding RAM.

See the Related Documents section of this document for more information about memory allocation.
Go to Part 3