If you’ve ever played with the aperture settings on a camera, you know that you can specify how shallow or deep your depth of field is. Depth of field relates to the plane of focus (the areas in a photo that are in front of or behind the focal point and that remain in focus) or how in-focus the foreground elements are when you compare them to the background elements.
The new Lens Blur filter allows you to give the effect of a shallower depth of field after you have already captured your image. This filter enables you to take a fully focused image and create this type of selective focus. You can also use it to create a kind of dreamy effect.