Macbook pro memory optimising?

[V-Spec]

I recently bought a MacBook pro to use mainly for photography. I upgraded it to 4Gb of ram, but I haven't noticed that much more of an increase in performance.

When I look in system performance whilst using photoshop/Aperture, I notice that the amount of free memory generally gets as low as 20-30Mb, with lots of swap file. But 1.5 - 3Gb of memory is "inactive"...

I'm not a memory expert, is there any way I can get this utilised? or is that the way it is, and i'm just misunderstanding it

Any help would be great

 

[V-Spec]

I did wonder if this was the case.

Thanks!