A blur estimation method and apparatus which utilizes Gaussian differences at multiple resolutions, upon which iterative convolution is performed to match sharpness measures between two images. Blur differences are combined with an iteration number selected from multiple resolution levels based on comparing a sharpness ratio as the blur difference estimate. Blur difference estimate is then applied through a depth model to arrive at a depth estimate. Blur difference depth estimation can be utilized for controlling operation of focus control hardware in an imaging device.