1. A method for acquiring an image comprising: acquiring a first image frame including a region containing a subject at a first focus position; determining a first sharpness of said subject within said first image frame; identifying an imaged subject size within the first image frame; determining a second focus position based on said imaged subject size; acquiring a second image frame at said second focus position; determining a second sharpness of said subject within said second image frame; determining a sharpness threshold as a function of image acquisition parameters for the first and/or second image frame; and responsive to said second sharpness not exceeding said first sharpness and said sharpness threshold, determining camera motion parameters and/or subject motion parameters for said second image frame before performing a focus sweep to determine an optimal focus position for said subject.