Please note that the propagation could be blocked somewhere in the subtree of an other. Just deactivate the Inherit permissions from parent objects option. If you do that, you can use whether you keep all the inherited entries as real entries, or if you need to remove all the inherited entries from the ACL. You can easily change the propagation value..
Thus in practice the scale space is computed by. Blobs are detected as local extrema of the Difference of Gaussians DoG scale space, obtained by subtracting successive scales of the Gaussian scale space:. At each next octave, the resolution of the images is halved to save computations.