The next installment of Photoshop Creative Suite 4 (CS4) will ship a 64-bit version as well -- but initially only for Windows Vista users and not Mac users, Adobe said. The reason Adobe gave is that many of the applications that make up CS4 are written in Carbon (development language) rather than Cocoa and Apple had said last year it will not support 64-bit in Carbon.

Commenting on this, John Nack, product manager of Adobe Photoshop, reportedly said that they have to rewrite from scratch, which makes the cost prohibitive as compared to that for Windows Vista. Adobe claims its preliminary testing revealed that the 64-bit version offers around 8 to 12 percent added performance over the 32-bit version. Nack explained that the real strength of 64-bit is that it lets you address a large amount of memory. The biggest difference can be seen when working with large files/images, or moving around a lot of data. Adobe claims using 64-bit could cut down the time it takes to open a large image from 200 to 70 seconds. However to take advantage of 64-bit, you need more than 4GB RAM allocated to Photoshop, Nack said.

In another announcement, Adobe said that its Photoshop Lightroom version 2 (for Windows and Mac) that just entered beta testing, will also be available in a 64-bit version. The 30-day free trial can be downloaded here.

Meanwhile, no details are out as to when Photoshop Creative Suite 4 for Windows Vista is shipping and it's too early days to say when the 64-bit version for Mac will be out, the company said.