The conscious application of shallow depth of field precedes photography. Vermeer did that!
Granted, he probably used a camera obscura that only needed a recording medium other than pen and paper in order to become a camera as we know it today.
Ever since Nièpce invented light-sensitive coatings, camps have been divided between naturalists of the f/64 persuasion who would like to foster the illusion of endless depth of field and subjectivists who regard shallow depth of field as one of the few distinctly photographic means of expression.
I count myself with the latter camp and therefore felt lucky to have snagged a Canon FD f/1.2 85 mm L lens off the ‘bay. Good degree of preservation, too.
Lacking a subject for portraiture, I shot this with the aid of two bathroom mirrors.
At f/1.2, naturally.