That is, a sine wave with a period equal to the size of the box will be blurred away entirely, and wavelengths shorter than the size of the box may be phase-reversed, as seen when two bokeh circles touch to form a bright spot where there would be a dark spot between two bright spots in the original image.
That is, a sine wave with a period equivalent to the size of the box will be completely blurred out, and wavelengths shorter than the size of the box might undergo phase reversal, as observed when two bokeh circles touch to create a bright spot where there would have been a dark spot in the original image.