I was thinking the other day about the old timey Instamatic and Polaroids, they managed through cheap optics to vignette the skies in the corner so they were a tidge darker which lent to helping frame the center of the image. Simple task in CS5 to duplicate.
Here I started with RAW images. Upped the clarity, vibrance and saturation so you got the look of the old Kodachrome or Polaroid films. Then I opened the image.
With the image opened up I created a layer. Then I used the oval tool and created an oval that went nearly all the way from top to bottom and edge to edge. I right clicked and selected invert. I right clicked again and went to the feather edges and went for the max feathering of 250 pixels.
The next step was to go down to the lower right corner and use the brightness tool and drop the brightness down until the corners began to darken...to taste by a factor of -50 to -75. I then used the merge visible. Et voila (that's rough French for "and there you have it") a knock off of an old Polaroid or Instamatic Kodachrome with a digital camera..
These images btw were shot out at Joshua Tree National Park over the weekend while hiking on Fathers Day. See why I said I need to go out there and spend more time there?