Neglecting Z-translation in Camera Shakes

Using projective gemotery it can be shown that the deviation of the blur kernel as a result of only z-translation lies within a pixel at any point in the image until,

tz > d / (x0-1)

where tz is the amount of z-translation, d is the scene depth and x0 is the x-coordinate of the image center. For a 6MP camera (x0 ~= 1500), the allowed z-translation is around 4mm for a depth of 6m. Typical camera shake motion shown in the anonymous work cited in our paper lies within this order of operating range. The following graph shows the plot of the allowed z-translation for different values of depth for a 6MP camera.

In our paper, we work with 768X512 sized images for which the operating range is almost the double of that shown above.