Methods and systems describe calculating an estimated focal point for a feature of interest within an ocular area of a subject using acquired test images and focal points. A curve is approximately fit to the defocus measurements located at different focal points. A maximum of the curve is identified that corresponds to an estimated focal point of the subject's iris. An image capture device can then record an approximately focused image of the iris using the estimated focal point. This reduces the time and computing resources needed to capture an image iris that is in focus where the subject may be located at a variable, unknown standoff distance. These methods and systems can be used for biometric identification using iris imaging, among other applications where quickly focusing an imaging system is advantageous.