Still raining but this time I've ventured as far as the front doorstep which is covered. I was able to perch next to the tripod and get some shots of movement with the camera in a fixed position, without getting soaked. Unfortunately there were parked cars, garden walls and general street furniture in the line of sight to contend with so the images are a bit cluttered. It is not the fastest stretch of road around but at least the cars are moving perpendicular to the camera position which gives the greatest possible lateral movement. I also made sure I only photographed cars moving at similar speeds of what I would guess to have been between 20-30mph to keep some consistency to the flow of images.
To guarantee I obtained evenly exposured images I set the camera to 'Shutter Priority' mode and the ISO to 'Auto'. This way even if I ran out of aperture sizes for the images with short exposure times, the camera would automatically adjust the ISO setting to produce an evenly exposed image. It is not a particularly bright day in Manchester.
|From top left clockwise: 1/500 sec, 1/250 sec, 1/125 sec, 1/60 sec|
|From top left clockwise: 1/30 sec, 1/15 sec, 1/8 sec, 1/2 sec|
I would conclude that for objects moving perpendicular to your position at between 20-30mph the minimum shutter speed to use is between 1/125 sec and 1/250 sec. You could use a slower shutter speed if there was a smaller angle of incidence or the movement was slower. Therefore quicker movement would require a faster shutter speed.
Having thought about this some more, I'm not sure if I am correct in saying the angle of incidence would make as much difference as I thought. While the object may not appear to be moving as fast relative to the camera position on one axis, it is instead moving more on the other (towards/away from you) which would have a similar effect on blur except it would be going into the image instead of accross it. Maybe I will try to do a comparison on another day that is less wet.