An electronic shutter for photographic recordings is also called a silent shutter because it does not require mechanical components and therefore does not cause any noise. In these cases, no movable components are required, because they are completely electronically controlled. The processes of exposure include resetting the light-sensitive elements, adhering to a predetermined exposure time during the light exposure and then reading out the sensor signals.
Electronic shutters are increasingly used as a supplement or replacement for mechanical shutters in still and movie cameras, provided that they do not work with photographic film, but with electronic image sensors.
With SLR cameras, a shutter releases noise is caused when taking pictures mainly by the mirror folding up and down. In the case of film cameras, the transport of the film in particular generates noise. Most high-quality standing and moving image cameras also have a mechanical shutter that obscures the image sensor or completely dims the lens and only releases it during the exposure time. A silent shutter is nowadays state of the art, especially for video recordings. With the silent shutter for still shooting, a camera is operated virtually in video mode without permanently recording image data. The image sensor is permanently reset, exposed and read out, to enable viewfinder images in live view.
Benefits of Electronic Shutter
- No noise when photographing or filming, which can be beneficial, for example, during theater or concert performances or when shooting wildlife.
- No shaking of the camera and thus no blurring of the images caused by so.
- No wear and tear of mechanical components.
- Especially with smaller image sensors, very short exposure times are possible (some cameras from Fujifilm as well as from the Sony RX series, or the Panasonic Lumix DC-G9, for example, can expose for 1/32,000 second). Conventional mechanical closures cannot expose so short.
- Enabling fast image acquisition series or multiple exposures, such as for continuous photography, focus stacking or tracking of objects, as well as pixel shift (multiple shots with slightly shifted image sensor) or high-contrast images.
- Due to the missing edges of the mechanical shutter, no undesirable effects are caused in the image by diffraction on these edges.
Cons of Electronic Shutter
- Many digital cameras today do not have CCD sensors for image acquisition, but CMOS sensors. CMOS sensors can only read the image lines sequentially, i.e. line by line or column by column. Due to the sequential reading of the image lines, geometric distortions can occur with moving motifs (Rolling Shutter Effect). The faster the image can be read, the less this effect is.
- Some digital SLR cameras have the option of triggering silently in Live View mode, but the optical viewfinder does not show an image.
- When shooting with flash light, it must be ensured that the flash light is evenly available throughout the recording. Flickering light sources, such as gas lamps, may cause uneven exposures in the image.
- Completely resetting the image sensor without exposure as with a closed mechanical shutter is not possible, so uninterrupted exposure can limit the dynamic range of brightness in the captured images.
- Furthermore, the user cannot hear when and if the camera triggers without additional acoustic signals.
With global electronic shutters, the image sensor can be read out completely and simultaneously, so some of the above disadvantages do not arise.