Variation of the contrast panel a) and the scale panel c) of the solar granulation (defined in Sect. 1) for the Hinode/SOT HOP 79 north-south scan of December 21, 2009. The field of view of the images is 1024 × 1024 pixels (112″ × 112″). Panel b) shows the variations of the “parallel scale” (+) and “perpendicular scale” (*) derived from the autocorrelation functions (ACFs) computed in the directions parallel and perpendicular to the polar limbs. “ACF mean” is the mean between ACF parallel and ACF perpendicular. A few images with dark columns and those containing the limbs have already been removed. The images at positions –543″ and +623″, which depart from a regular variation in panel c) and which, visually, appear clearly out of focus, will be removed.