Digital Photography

The Shutter controls many aspects of the final image. It can freeze motion, allow motion blur to show movement, it can create striking nighttime images, and it controls the amount of light striking the photo sensitive element.

The older cameras used an interleave (Focal Plane) type shutter to open and close in front of the film plane.

These shutters were cocked with a manual handle and release with a small Shutter Release Button. Normally the opening would be closed until the release button was pressed. Typical shutter speeds were B (Bulb), 1/30 sec, 1/60 sec, 1/125 sec. The shutter speed was matched with the ISO of the film and the subject to be captured. The exposure was controlled by the Aperture setting on the lens.

The major limitation of the Focal Plane shutter was the maximum speed the shutter could open and close. This was a mechanical operating problem that could not be resolved with this type pf shutter mechanism.

The Shutter Curtain
When film manufactures created fast ISO films the camera manufacturers developed an new shutter device, named the Shutter Curtain.

Modern digital cameras have one, or two shutter curtains; the primary curtain (1^st Curtain), and a secondary curtain (2^nd Curtain). the primary curtain controls shutter speed for the majority of exposures. The secondary curtain normally syncs with the flash to produce an action movement during the initial exposure, while the secondary curtain is synced with the flash to produce stop action on the final exposure.

The illustration above shows a basic shutter curtain with a pre-defined gap to allow light to strike the sensitive device. The gap opening passes in front of the sensitive element at a prescribed speed, this allowed shutter speeds up to 1/4000 sec. Faster shutter speeds were created by varying the gap distance to smaller dimensions and varying the speed of the primary curtain.

Keep in mind that any adjustment to the Shutter Speed will have a major impact on the exposure of the image; for modern digital cameras using semi-automatic settings the camera will calculate the shutter exposure requirements and adjust the Aperture values for the best overall exposure.

If you are using Manual settings you will have to make all the adjustments manually yourself using the cameras' exposure metering system. This will take you back several decades in photography science and technology, but when mastered can capture some very artistic images.