1. An image processing method comprising: receiving a user input indicating first and second areas of interest in a preview image; receiving one or more transition inputs indicating a transition of focal settings between the first area of interest and the second area of interest; determining focal settings over the preview image based on the user input and the transition input; and deriving a parameter to capture an image that conforms to the determined focal settings, wherein the parameter to capture an image is an aperture mask that defines two or more aperture settings for an aperture array.