In the early days of photography, the lenses and fixing techniques (e.g., daguerrotypes, emulsions) available required long exposure times. This fundamentally constrained the types of photos that could be taken, but it also meant that certain approaches to photography were popular that very few people would attempt today.

For example, long exposure portraiture: with fast lenses and films, we have come to expect portraits to capture a person in a moment. This means a sharper, clearer, and less posed, more spontaneous picture. Snap-shots freeze momentary expressions and actions.

They also ask much less of the subject. Rather than requiring a subject to pose for several minutes, the picture is taken in a fraction of a second. No one would think to pose for a daguerrotype these days.

In "A Small History of Photography," Walter Benjamin discusses the way that the technical constraints of early photography created qualitatively different portraits in his description of Hill's portraits made in the Edinburgh Greyfriars cemetary:

But this setting could never have been so effective if it had not been chosen on technical grounds. The low light-sensitivity of the early plates made prolonged exposure outdoors a necessity. This in turn made it desirable to take the subject to some out-of-the-way spots where there was no obstacle to quiet concentration...The procedure itself caused the subject to focus his life in the moment rather than hurrying on past it; during the considerable period of the exposure, the subject as it were grew into the picture, in the sharpest contrast with appearances of a snap-shot...

--"A Small History of Photography," Walter Benjamin

In other words, the materiality of the camera radically affects the subject matter of the picture, both in how the photographer approaches the portrait and how subjects present themselves. It is not only a practical consideration, but a conceptual one.

My Long-Exposure Portraits

A Series of Miris

More Portraits: Jon and Jamie