I go on an overseas trip and buy a new camera while there. I declare it (when returning to my country of origin) upon going through customs. I pay a duty.
I go on an overseas trip and buy a new camera. I don't declare it. Now I pay duty, plus a fine or some other penalty for (let's be honest, smuggling.)
I go on an overseas trip and take a nice camera with me. I don't declare it, as I shouldn't have to. If a customs agent finds it, I may have to argue my case. If I'm unconvincing, chances are I pay duty and a fine. Shouldn't have to, but hey, it's on me to prove it's not dutiable.
Now for my question. Should I declare it, as a non-dutiable thing? or does that presume guilt/duty?
(This is a subjective question, so if closed, I won't quibble.)