Some practices that go before pressing the shutter that may improve control and results on final images
Using Petzval-type lenses for portraits when the subject's face is out of the center of the image requires some care. The article discusses and gives an example of how to decentralize the lens to reposition its optical axis over more peripheral areas of the photographic frame.
The practice that I will describe is the one that allowed me to take some reasonable pictures of seagulls in Hamburg harbor in Germany in 2008. Later, in other occasions, it served me again and I lost less time to catch some images birds flying. That is the case, to my level of requirements, of...