Method of providing a sharpness measure for an image

An image processing device arranged to, and comprising the steps of:

• detect an object region within an acquired image;
• obtain meta-data for the acquired image;
• scale the chosen object region to a fixed size;
• calculate a gradient map for the scaled object region;
• compare the gradient map against a threshold, wherein the threshold for the acquired image is a function of at least:
• a contrast level for the detected object region, a distance to the subject and an ISO value used for image acquisition;
• determine a sharpness measure for the object region as a function of the filtered gradient map values, the sharpness measure being proportional to the filtered gradient map values;
• and
• responsive to the sharpness measure indicating the object region is not sufficiently focussed, change focusing for acquirinq a subsequent image.