Shutter release delay
In photography , shutter release delay is the time that elapses between pressing the shutter release button on the camera and the actual start of image recording . In cameras with autofocus , the shutter release delay is essentially determined by the speed of the automatic focusing.
The shutter release delay is a design-related feature and, depending on the technology used, is made up of different components in a camera, partly mechanical, partly electronic.
Pressing the shutter release sets a whole series of mechanical processes in motion in both conventional and digital cameras :
- With some older viewfinder cameras , the central lock is cocked (no longer common today);
- in cameras with autofocus , a motor adjusts the distance setting determined;
- With some viewfinder cameras and all SLR cameras with open aperture measurement, the working aperture is set;
- single-lens reflex cameras with an oscillating mirror swivel it out of the beam path;
- With mirrorless digital system cameras , the focal plane shutter , which is always open for viewing the subject in the electronic viewfinder, is first closed and the image sensor is deleted;
Only now can the shutter be opened and the actual exposure begins.
With modern cameras, exposure measurement and setting take place almost instantly. However, some SLR cameras correct the exposure settings again immediately after closing the lens aperture and insert a short delay time for this, for the Minolta XD series, for example, approx. 60 ms . Modern cameras trigger after focusing, including all other mechanical delays, in less than 200 ms, sometimes with significantly less than 100 ms delay.
Influence of the auto focus
Significant differences in the shutter release delay result from the autofocus method. A distinction must be made here between two families, contrast AF and phase AF . The time required for arming must be added to the delays mentioned above.
The older phase comparison method, which is already widespread in film-based cameras, works with separate sensors according to a triangulation method and in most cases can adjust the camera lens directly to the desired motif, since the required adjustment direction results directly from the measurement method. Most digital SLR cameras and all film-based cameras with passive AF use this technology. Some digital compact cameras with an additional phase sensor were also on the market. Cameras with phase AF usually achieve setting times of less than half a second, sometimes less than 100 ms, depending on the lens used and lighting conditions.
When focusing using the edge contrast method, the camera continuously evaluates the image generated by the camera sensor . In addition to the considerably greater computational effort, this has the inherent disadvantage that the autofocus has to approach the correct setting and, under certain circumstances, controls it back and forth several times. In unfavorable lighting conditions, strong sensor noise can also impair the function. In the case of simpler digital cameras, this process can take several seconds, even in good lighting, and even high-quality system cameras require a noticeably longer time than cameras with phase AF. The AF in the live view mode of most SLR cameras also works with contrast AF and is therefore comparatively slow.
Since the end of 2012, mirrorless digital system cameras have been available that eliminate the disadvantages of contrast AF with phase sensors integrated into the image sensor. You can achieve similarly short delays through AF as single-lens reflex cameras.
While current digital SLR cameras have shutter release delays of 0.2–0.5 seconds, in the area of compact digital cameras, depending on the model and recording conditions, shutter release delays of up to more than one second must be expected.
The Ricoh company circumvented the problem with some models by using a so-called hybrid autofocus. An additional AF sensor, which is independent of the recording CCD, is used here, as has been known from conventional AF cameras for many years. With normal shooting distances, this technique can achieve a delay of less than 0.1 seconds. However, due to the nature of the system, this method does not work for close-up and macro shots; the cameras then evaluate the CCD relatively slowly.
Information about the shutter release delay is mostly missing in the data sheets of the camera manufacturer; More realistic information can usually only be found in independent test reports. If manufacturers provide this data, the shutter release delay after focusing is usually meant, as the influence of different shooting conditions and the use of different lenses do not allow a fixed specification.
The shutter release delay of cameras disrupts spontaneous snapshots or makes it completely impossible. The following approaches can be tried:
- The photographer can try to anticipate a situation worth photographing and trigger it earlier by the factor before the desired image is actually created.
- A second approach is to always make series recordings and to trigger them a few seconds or fractions of a second in advance; In doing so, however, the image sequence time of the camera must be taken into account, otherwise the camera's buffer memory is full before the desired image could even be recorded.
- Most digital cameras have a two-stage shutter release: In the first stage, focus and exposure are saved, and only in the second stage the recording is released with only a very short delay. In practice, this can be applied as follows with many cameras: In expectation of an interesting situation, the shutter release is tapped and held - this overcomes the first stage. When you then press the shutter button fully, you only have to overcome the shorter delay of level two.
- Some compact digital cameras have a snapshot setting in which the lens is permanently set to a medium distance, usually the hyperfocal distance , so that, for example, from a distance of around two meters “everything is in focus”; there is no delay caused by the autofocus. The same technology can also be used with manually focusable lenses of all other cameras.
- Some cameras support a function, usually called a focus trap , in which the focus is manually on a certain point and the camera is released almost instantaneously as soon as a moving subject passes this point.
Deliberate use of a shutter release delay
The self-timer enables a deliberate shutter release delay . After you press the shutter button, the camera waits a few seconds for the picture to be taken. The user of the camera can use this period of time, for example, to position himself in front of the lens in order to also appear in the photo. In cameras that no connection for a wire or remote shutter having the self-timer can also be used as a last resort to when shooting with a long exposure time of the tripod of the camera shake to prevent.
Some camera models offer a flash function to reduce the red-eye phenomenon. The camera first emits a pre-flash , the actual flash exposure takes a moment later.