An imaging device comprises a lens barrel having a lens opening, and a lens positioned in the lens opening of the lens barrel, the lens having an optical center, a focal length F, an aperture diameter D, and an aperture number FN=F/D. An image sensor comprises an array of light sensing pixels that each have a dimension P, the sensor spaced apart a distance S from the optical center of the lens such that a focus offset gap X=F−S. The pixel dimension P and aperture number FN are selected such that 2·P·FN≧X.