
Originally Posted by
John Chardine
Unfortunately, the answer is not black or white Artie. If the file you are working on in Photoshop is pretty small, say a 10 mp image from the 1DmkIII, you will not likely see a difference in performance between 4 and 8 gb of memory. The reason is that the file can fit into available memory without having to resort to being "paged out" to your hard disk. If the file was large- say a 5D mkII image that you have upsized, then you would likely see a difference in performance. As Peter and Arash suggest, paging out to the hard disk is the kiss of death for performance so you want to avoid this at all costs.
One way to reduce the chances of paging out is to adjust the amount of memory Photoshop will use. Go to Preferences-Performance and adjust the "Let Photoshop use" slider to use more memory.
As a general rule the more memory you have the better so if you can afford 8gb, then "fill your boots" as they say.