You say "Compute areas in the 2nd column.".
In my book 2nd column has index 1, I think you mean 3rd column here.
Also: you compute the blob radii, not areas, right?

From the `blob_*` docstrings it's not clear to me why sometimes the blob radius is `sigma` and why sometimes it is `sqrt(2) * sigma`. I presume this is explained in the external references, which I didn't follow, but maybe you can just re-state it in a comment here that this is the reason you multiply by `sqrt(2)`?