Photoshop CS4 64-bit Versus 32-bit
Adobe Photoshop CS4 for Windows comes as both a traditional 32-bit application and a 64-bit version for systems with the processor and operating system to run 64-bits. I recently upgraded to a Quad core 3.0 GHz Q9650 system with 8 GB RAM running 64-bit Windows Vista. If you're curious what I think of 64-bit Photoshop, read on.
Installation was a snap. A single install gives you both 32-bit and 64-bit versions of CS4. They end up right next to each other on the Start menu as "Adobe Photoshop CS4" and "Adobe Photoshop CS4 (64 Bit)." When it comes to starting Photoshop, the icon is the same for both versions so if you're not paying attention you likely won't be able to tell which you are running. Splash screen while loading looks the same too as does the Help >> About Photoshop screen. Indeed, the 32-bit and 64-bit versions are virtual twins of each other so you may be wondering what the point is.
For memory intensive applications such as Photoshop, 64-bit applications should be faster than 32-bit since the extra bit width gets you past the 4 GB addressing limit of 32-bit. But even with losing a good chunk of those four gigabytes to Windows itself and you video card you still have a good 2 GB to run Photoshop in. Unless you have a combined total of around a gigabyte of images open at the same time, you will be unlikely to see any benefit from 64-bit addressing. Adobe estimates that the average performance improvement is in the range of eight to twelve percent but I honestly can say I've even seen that. For extremely large files though, the difference is noticeable. My largest image files generally top out at three quarters of a gigabyte but if I open a few of them at the same time the 32-bit version does begin to bog down while the 64-bit version does not.
But running 64-bit Photoshop all the time does have a significant disadvantage in another area when compared with 32-bit. As of this writing, very, very few third-party filters are compatible with 64-bit Photoshop. You don't get an error message or anything, it's just that even if the installer for that plug-in lets you install it into the 64-bit Photoshop folder, Photoshop itself will simply ignore it. It won't even show up grayed out on the Filter menu – it's as if you never even installed that plug-in.
A few companies are coming out with 64-bit versions but many have not so far. Even bit outfits such as Nik Software and onOne haven't yet. Among plug-ins I do use, NeatImage now has a 64-bit version available for a cost and PixelGenius has a 64-bit beta version of their PhotoKit Sharpener available. HDRsoft's Photomatix Tone Mapping plug-in has a 64-bit version but the stand-alone Photomatix is still a 32-bit application. I really don't use that many plug-ins but this can be a pain. Others that have stepped up to the 64-bit challenge include PictureCode's Noise Ninja and Topaz Adjust.
And no, the two versions of Photoshop do not share the same plug-in folder. The 32-bit and 64-bit versions are completely separate programs with completely separate settings and everything. What you change in Edit >> Preferences in one has no effect on the Preferences for the other. Plug-ins and other add-ons for one have nothing to do with the other. I'd recommend creating a folder called "Photoshop Third-party Plug-ins" and using it as the destination for installing any 32-bit plug-ins you'd like to be able to get at from both. You can then go into Edit >> Preferences >> Plug-Ins and configuring the Additional Plug-Ins Folder to point there.
On the OS X side of things, there is no 64-bit Photoshop. Not yet at least. In the end, whether you believe that Apple pulled the rug out from under Adobe by cancelling 64-bit Carbon at the last minute or whether you think that Apple had long been putting out enough clues that even a blind man could see that folks should be moving to Cocoa doesn't matter. The net effect is the same thing. For now at least, native 64-bit support for Adobe Photoshop CS4 exists on the Windows platform only.
With sensor resolution increasing with each new generation of camera Nikon and Canon releases, 64-bit is clearly the direction of the future but for now I'm pretty much sticking with the 32-bit version of Photoshop running on 64-bit Vista. If I really need the extra headroom I can always fire up 64-bit Photoshop for a specific task, but for most image optimizing tasks 32-bit seems just fine for now.