“The next shell fell even closer. I didn’t dare to take my eyes off the finder of my Contax and frantically shot frame after frame. Half a minute later, my camera jammed—my roll was finished. I reached into my bag for a new roll, and my wet, shaking hands ruined the roll before I could insert it in my camera.”
 
“I paused for a moment…and then I had it bad. The empty camera trembled in my hands.”
 
“The rip tide hit my body and every wave slapped my face under my helmet. I held my cameras high over my head...and told myself, “I am just going to dry my hands on that boat.”
(Robert Capa, Slightly Out Of Focus).

And than there is the focus blur made with the (even intentional) wrong evaluation of the distance between the eye of the camera and the objects: the photographer, usually using long lenses and wide apertures in manual mode decides not to focus on the subject. The subject is intentionally unfocused.


Daido Moriyama
“For me, capturing what I feel with my body is more important than the technicalities of photography. If the image is shaking, it’s OK, if it’s out of focus, it’s OK. Clarity isn’t what photography is about.”  (Daido Moriyama)

William Klein


Trent Parke

Bruce Gilden

Blur can be created also panning the camera, moving the camera laterally to follow the motion of the subject to create a fairly sharp subject on a blur-streaked background. Or locking down the camera to create a sharp background and a highly-blurred subject.
The camera shake can be combined with the use of a strobe. You can combine long exposure and zooming, long exposure and strobe, or long exposure, strobe and zooming of the camera, creating different kinds of ghost effects, mix of sharp and blurred, lines and streaks of light. 
Blur can also be post-produced, in the darkroom - Mimmo Jodice for example created his blur effect moving the enlarger, bringing to life the faces of antiquity - or in photoshop.


Mimmo Jodice

Blur can be a valuable story-telling tool. It inserts a direct trace of time in the image. It plays with the boundaries separating reality and the representation, vision, dream of it.
It can demonstrate the speed of a fast-moving subject, or communicate anxiety with a bit of camera shake, or even create a dynamic attention-grabbing special effect via zoom blur. It can transform subjects in abstract forms or in concepts.
Blur can be employed in street photography too.
This selection will show you: