This is incorrect:

  - (void) dealloc
  {
    self.caption = nil;
    self.photographer = nil;
    [super dealloc];
  }

Using the dot syntax will invoke a setter whose implementation might change if the class is subclassed, which can be the cause of subtle errors. Also, if you're using KVO (Key-Value Observing), invoking the setter might notify observers who then try to work with a (partially) deallocated object.

This is standard:

  - (void) dealloc
  {
    [caption release];
    [photographer release];
    [super dealloc];
  }