Different magnetic fields with different pickups

[PunkKitty]

 

[Coralkong1]

Sorry to sound daft, but what does that mean?
The fields all look pretty similar to me, or am I supposed to be looking at the (what I assume to be) iron filings?

And I don't see a HB example.

Please explain.

 

[Bob411]

Sorry to sound daft, but what does that mean?
The fields all look pretty similar to me, or am I supposed to be looking at the (what I assume to be) iron filings?

And I don't see a HB example.

Please explain.

Pretty sure image is from this: It promises HB but, doesn't show it.