1. A method of determining a depth measurement of a scene using an optical blur difference between two images of the scene, each image being captured using an image capture device with different image capture device parameters, said method comprising: identifying a corresponding image patch from each of the captured images, motion blur being present in each of said image patches; determining a kernel of the motion blur in each of the image patches, the kernel of the motion blur in at least one of the images patches being used to generate a difference convolution kernel; convolving a selected first image patch with the generated difference convolution kernel to generate a modified image patch; and determining a depth measurement of the scene from an optical blur difference between the modified image patch and the remaining image patch.