There are occasional situations when creating an artificial vignette effect can help an image. This was the case with this image and it may be more common in similar situations which can be lumped together as “intimate landscapes”. These are typically small scale landscapes. The kind Elliot Porter pioneered.
A vignette should be subtle. It is a bit strong in this image for demo purposes. It may help to draw the attention to the center of an image where the action is and make it harder for the eye to accidentally ‘wander off’.
There is a quick way to do this in PS CS-5. In the ‘Layer’ panel: choose ‘Duplicate Layer’. In the Filter panel choose ‘Lens Corrections’. Once this window opens choose at the top ‘Custom’. Then adjust the sliders for the amount and radius of darkening as seems appropriate. Then click OK. Then go to the Layers panel and flatten the image. Naturally you don’t want to do this if you have no original or RAW copy of this image saved. If your camera model is not embedded in Photoshop, it may take a bit longer for the image to load, so be patient.
This was a shot taken in Georgian Bay. It shows the white pine during the time its pollen float on the water surface like green (but healthy!) scum.
Sony ILCE 7R with 24-70 Zeiss Vario Tessar at f20, ISO 400, 1/15th sec.