1. A method of identifying whether a plurality of image frames may contain a common object of interest comprising the steps of: receiving a plurality of image frames in an image processing apparatus wherein said plurality of image frames are generated by at least one imaging device; applying at least one filter to each of said plurality of image frames to generate a discrete output value, wherein each filter screens for a differentiable characteristic associated with an object of interest that is unique to that filter; and using said image processing apparatus to identify image portions from said plurality of image frames that exhibit said differentiable characteristic in response to a logical combination of said discrete output values for each of said at least one filter for said plurality of image frames as potentially having a region of interest representing the common object of interest.