The conjugation of the verb 'Show' is : "show -- showed -- showed / shown".
[The oId & archaic spelling of 'show' is *'shew'. Its conjugation is : "shew / shewed / shewed or shewn".]
The past participle "showed" is very rare. It may be used in mediocre A.E. active construction; but it should NOT be used as per standard B.E.
Active voice : I showed my camera to my friend.
Passive voice : My camera was shown (NOT, was showed) to my friend by me.
The phrasal verb "show up" means 'to arrive' : He showed up, apologising for being late'.
But the phrasal verb "show out" means 'to present oneself especially in a public and performative manner' : 'The actress always showed out with a charming and extravagant outfits.'