I've recently been asked the following question:
Why are second order edge detectors better at finding edges than first order detectors?
The problem is, I cannot see why! Second order filters are always more sensitive to noise (e.g. laplacian filter), and the same and better results can be obtained when a first order (e.g. sobel filter). Not only is there less noise but the edges appear to be better.
Could anyone shed some light on the matter or give their opinion?