How to detect what type of filter is used

In week 1 Quiz1 Q1 of DLS course-4 we say over which axis of the filter matrix do we see the delta value, what does that mean?

This is based on the example Prof Ng gives in the lectures of how you could design a filter to detect vertical edges. Once he’s given that example, he then explains how you would apply the technique to detect horizontal edges or diagonal edges. Compare the sample filters they give here to the example Prof Ng showed us. What does it look they will detect based on that comparison?

One general point worth making here is that the “handcrafted” vertical edge filter is just an example to demonstrate how convolutions work in general and why they can be useful for detecting things. That’s very “old school” and nobody uses handcrafted specific filters like that anymore: you just randomly initialize all the filters and then let the patterns be learned through the training using back propagation.

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