As the resolution of digital cameras continues to increase, so too do file sizes. And when image files get bigger, optimizing them can put more of a burden on Photoshop and your computer. If you're looking for some ideas to speed things up, hopefully you will find at least a few items of interest in this week's PhotoTips article.
Close unneeded applications and files
The data for every program and file you open on your computer has to live somewhere. The image you are editing has to compete with all of them for space in your system's memory. You can speed up your editing tasks by closing any images you are not working on as well as any programs you don't need for the time being.
Add more RAM
If things still run slowly, you may be able to add more memory to your computer. The cost of doing so has steadily been dropping and you may be surprised at how affordable it is now. You can buy memory from a variety of sources, just be sure you can tell what kind you need for your system.
Get a new video card
Photoshop is a graphically intensive application that puts heavy demands on your video card. As memory prices continue to drop, manufacturers have started putting more and more memory on their video cards. If you have an older card, you can likely speed things up by upgrading to a newer video card with more memory. You don't need 3D high performance, but additional memory can help even with 2D applications such as Photoshop.
Clean up and defragment your hard drive
When a file gets written to your hard drive, it has to go where there is room for it. If there isn't a big enough hole for the whole thing, your computer will be forced to split it up into pieces, putting things where it can. Over time, this can make a mess of your drive, slowing things down as all those pieces later have to be put back together again so you can use that file. Defragmenting your drive can speed things up by rearranging things to put all those pieces back together again. Deleting files you don't need can provide more space for saving those you do.
Setting Scratch Disks
What is a scratch disk? A scratch disk is similar to a virtual memory in a Mac OS. So for the best performance possible, you must set the primary scratch disk to an already defragmented hard drive that is not used to run the operating system as well as having a good amount of unused space. It should also have a fast read and write speed.
Move your scratch disk to a different drive
Photoshop uses space on your hard drive for its "scratch disk," a place where it stores needed data that won't fit into your computer's memory. If you move this to a dedicated drive, it will take less time to read and write from it by avoiding contention with other processes. You can change the location of Photoshop's scratch disk by going to Edit >> Preferences >> Plug-ins & Scratch Disks. By default, Photoshop will write this data to the startup drive for your operating system but this is a poor choice if you have more than one drive. The ideal location would be a drive other than where your operating system is, and other than where any large images are that you may need to edit. If you have a lot of drives, you can specify up to four for Photoshop's use.
To tell if just how much the current image is needing to use your scratch disk, you can select "Efficiency" from the pop-up menu accessed via the standard triangle icon in the lower left-hand portion of the image's border. The more this efficiency rating drops below 100%, the more often Photoshop has to rely on your scratch disk. More memory or fewer open images and other programs will let you avoid the scratch disk more often, but when you need the scratch disk you'll be glad it's on a defragmented drive that isn't heavily used for other things. "Scratch Sizes" on this same pop-up menu will show you just how much space you are currently using in RAM and your scratch disk combined. You can also change this to "Timing" to tell just how slow (or fast) your performance really is. Photoshop will update this with the time it took for each action. You can also add these to the Info Palette by using the pop-up menu triangle for it. If you can't find your Info Palette, select Window >> Info from the main Photoshop menu bar.
Change Photoshop's Memory Allocation
Photoshop tries to be a good citizen, playing well with other applications on your computer. One of the ways it does this is by not using more memory than you let it. Edit >> Preferences >> Memory & Image Cache will let you change this setting. Optimizing this may take some tweaking. If you set it too low, you might not be making the most efficient uses of the memory you have in your computer. If you set it too high, your operating system will be starved for memory and slow everything down. The default is 70%.
Tune image caching preferences
To facilitate zooming, Photoshop caches various views of your image. Doing so can speed up zooming if you have enough memory, but will definitely slow things down if you don't. The default is to cache four levels, but if you're cramped for space, consider setting this to a lower value. Setting it to one disables caching since only the current view will be in memory. You can change this setting by going to Edit >> Preferences >> Memory & Image Cache.
Turn off "Maximize PSD and PSB File Compatibility"
Adobe kindly provides this feature to allow old versions of Photoshop to be able to read files written by newer versions to the extent possible. But having this turned on will increase the size of your files by inserting a full-scale flattened copy along with the actual image layers. And creating this extra layer will take time, slowing down the process of saving files. Unless you know you need this level of backward compatibility, I'd suggest turning this setting off by going to Edit >> Preferences >> File Handling. If you find later that you do need this capability, you can always resave a given image after turning Maximize Compatibility back on.
Minimizing Palette Preview Thumbnails
Photoshop uses extra memory to display the thumbnail previews in the layers, paths and channels palettes so the more preview thumbnails that Photoshop displays and the larger their size, the more memory is being used to draw and update them. To minimize these previews, click on Palette Options from the Palette pop-up menu then select the smallest size or none for the thumbnail size and then click OK.
Don't export the clipboard
Photoshop uses its own facilities to drag and drop data between open images, but must rely on your operating system's clipboard to interchange data with other applications. If you have no need to copy and paste between applications, you can turn this off to save CPU time. You'll find it under Edit >> Preferences >> General.
Reduce the number of History states maintained
The History Palette is a marvelous invention but it is not without cost. Each entry takes up memory that could be used for other things. If you're short on memory, consider reducing the number of states maintained by the History Palette. This one is at Edit >> Preferences >> General.
Check for updates from Adobe
Adobe periodically releases updates to Photoshop to fix various bugs or to improve performance. If you don't have Photoshop configured to do so automatically, check if there are any new updates you need to apply by selecting Help >> Updates... from the menu. Updates are often available this way before they are posted at adobe.com/downloads.
Merge some layers
I generally prefer retaining all image layers and adjustment layers to allow me the maximum ability to tweak things later without degradation. One way to speed up Photoshop that I haven't mentioned though is to merge some layers to create a smaller file that takes up less memory to open. Once you do so and save it there's no going back so think carefully before you do so but if you must, you must.
You probably won't need to make use of all of these ideas but those that make sense for your needs can help get your work done more quickly. If you do end up doing all of these and Photoshop still seems sluggish, it's probably time to start shopping for a new computer. One can only put off the inevitable for so long.
Adobe has Support Knowlegebase articles on optimizing Photoshop performance for both Windows and Mac OS on their website. Most of what they contain that isn't already covered here isn't overly relevant to photographers, but may be worth a look if you want some additional ideas.