A Boggart's Power

[angeleevee22]

No: HPFGUIDX 31225

I'm sorry if this has been brought up before, but I was thinking about 
this last night, and it's rather bugging me, so here goes -

What is the extent of a Boggart's power?  Harry trained against one 
when he was learning to ward off the Dementers.   When he saw one it 
changed into a Dementer, and he could, like with the real ones, hear 
his parents being murdered.  This suggests that the Boggart can 
manipulate the power of the thing one fears most, as well as 
appearance.  However, if that were the case, why wouldn't the full 
moon that Lupin saw have the same power as the real one?  Why 
didn't the sight of it trigger his transformation?  Does this make 
sense?  Please help me out;

-Tabby