Our eyes have a fixed refresh rate of about 1/30th of a second. Modern cameras today have shutter speeds that range from 30 seconds to 1/8000th of a second. The shutter is the third component of a photographic exposure. It controls the amount of time the sensor receives light. Creatively, the shutter can freeze a moving object or let it blur. The longer the shutter is open, the more movement will show. A faster shutter speeds can stop action.
Shutter speed & the amount of light
In previous posts, I’ve explained that an f/stop is a measure of the amount of light. Increasing the exposure by one f/stop (or just “stop,”) doubles the amount of light. Decreasing an exposure by a stop cuts the quantity of light in half. It’s very easy to see this in a chart of shutter speeds. If you start at say, 1/30th, a move to the right doubles the speed. 1/60th is twice as fast as that 1/30th. Move to the left and the speed becomes longer–twice as long in fact. 1/15th is half as long as 1/30th.
Short duration shutter speeds, those 1/250th and faster are perfect for freezing fast moving subjects. Subjects moving across the frame, like planes at an airshow, require shorter shutter durations than one heading toward or away from the camera.
1/2000th is a super fast shutter setting. It completely freezes the swiftly flying AT-6 Texan planes. Below, the downside of this high speed action stopper shows. The orange plane is taxiing along side of the runway. Without knowing that the plane was in motion, someone looking at this picture, would see a parked airplane with the Aeroshell aerobatics happening in the sky behind it.
While most motion stopping happens at or faster than 1/250th, a subject that has hit it’s peak action can be stopped with a slower shutter. Jumping subjects are great examples. Release the shutter at the top of the jump when the subject has stopped for a fraction of time before falling back down.
Forward motion & peak action
A subject moving parallel to the camera requires a higher shutter speed due to the forward motion still happening at the peak of the jump.
Slow speed for motion blur
Photographs made with shutter speeds that are really slow take the view into a new worlds. When I was shooting film during the last millennium, I would prop a camera on the dashboard and shoot out the windshield of my car while I drove through brightly lit streets. This led to a project for a trucking company, U.S. Express. I mounted a Nikon 8008 with a 24mm f/2.8 Nikkor lens outside the cab of a semi tractor. The truck’s mirror was angled so the model appeared in it for the camera. I put a gas powered generator in front of the trailer hitch to power the Comet electronic flash power pack that charged the flash head aimed at the logo below the driver. A Vivitar 283 was aimed at the model’s face. I sat in the back using a remote electric cable release to fire the camera. The rig’s actual driver sat in the passenger seat telling the model how to drive the tractor. We drove slowly up and down Atlanta’s Buford Highway so that traffic would pass us in the lanes on the left.
Slower speeds add visual movement to photographs
When the relative motion moves parallel to the camera, more blur is apparent even at a higher shutter speed.
The time the sensor sees light can be action stopping, motion making or abstractly magical. My next post covers using the long exposures for art.