Some additional thoughts on imposed parallelism.
A big no no with architectural photography is to have vertical slightly converging.
Just a note on this, I worked for a number of years as an assistant for very well published architectural photgrapher in NY - as well I was in the past an architectural renderer (in the Ecole/Beaux Arts tradition) in my architecture practice. There are reasons why that typically they are straightened...again there are
reasons...one of which is that it creates stasis for viewer of page...there are others. To wit, not every photograph with architecture is destined for books and magazines on architecture....not every photograph of a building/arch. requires parallel verticals.
A big no no with architectural photography is to have vertical slightly converging. It looks best to either have straight verticals are else go hell for leather and have the verticals completely inclined.
On imposed absolutes. My late father in law, the reknowned American photographer Ted Croner
http://www.apag.us/apagwp/ted-croner/ shot one of the most iconic images in American photographic history usually referred to as Burning Buildings (you can see it at link bottom row left) - it was the cover image for Jane Livingston's seminal book "The New York School Photographs" and is in collection of Museum of Modern Art, The Met, and many others. On same web page is this image "Home of the Brave" also one of his most important images...again without parallel verticals. No one ever questioned the fact that the verticals were not parallel...and I will tell you that if anyone approached him with such a question...he would have just walked away.
I will p.m. you later with some examples showing the effects of parallelism and non-parallelism - with notes about both effects. I think it might be helpful.