Mirror lock-up
As a mirror up (short SVA ; English MLU for mirror lock-up also MUP for mirror up ) refers to the possibility of the oscillating mirror of an SLR some time before the actual recording to fold up. This reduces blurring caused by natural vibrations in the camera. Common areas of application are e.g. B. Night shots .
use
Basically, the mirror lock-up is used together with a tripod or similar. used. It is used to reduce vibrations, especially with shutter speeds in the range from 1/30 to 1/2 second.
When the camera is triggered, the mirror is swiveled out of the beam path. The jerky panning shakes the camera, which can affect the sharpness of the image due to blurring . This effect occurs in particular when using lenses with long focal lengths and / or long exposure times , which above the free-hand limit (1/60 sec at normal focal length), from which a tripod should be used, and below the shutter speeds of long-time exposure (1 second or longer ) lie.
With shorter exposure times, the shutter is closed again before the camera shake affects the image; with longer exposure times, the time in which the camera has been dampened again and is at rest predominates. However, mirror lock-up should also be used for long-term exposures.
By folding up the mirror prematurely, the camera or mount (tripod, etc.) has time to stabilize again. In practice, this effect is only noticeable when using a tripod, as otherwise completely different causes can lead to blurring or blurring .
Mirror lock-up is used in particular in night and astrophotography , as blurring is particularly pronounced due to the dark background.
Mirror lock-up is always used to test the performance of lenses and cameras under laboratory conditions .
handling
There are various methods of mirror lock-up, which differ in terms of handling.
- With older camera models, the mirror is manually folded up using a separate lever and usually remains in this position after the shutter release, so it has to be reset by hand (e.g. Nikon F , Minolta SR-T 101 ). The advantage of this variant is the absolute locking of the mirror in a folded-up position, which is necessary, for example, when using lenses that protrude into the mirror box.
- A further development is a mirror pre-release, in which the mirror is folded up by the energy used for the normal oscillation process by actuating a pre-release lever, but the shutter is not released, and this is only done by the normal shutter release. (e.g. Kiev 88).
- Modern cameras automatically delay the release of the shutter by a partially adjustable time and automatically fold back the mirror after the picture has been taken (e.g. Nikon D100 ).
- In mirror lock-up mode (MUP, Mirror up ), other cameras fold up the mirror the first time the shutter release button is pressed. A second press of the shutter release takes the actual picture, after which the mirror automatically swivels back into the beam path. To save energy, the mirror folds back after a certain time even if no picture is taken (e.g. Nikon D200 ).
Mirror lock for other purposes
The function is sometimes referred to as mirror locking or mirror locking . These terms are misleading because they are not used for the immediate triggering process, but for technical or maintenance purposes.
Old super wide angle
Originally, however, the purpose of this device was different. Certain lenses , especially older wide-angle lenses and fisheye designs, had lens groups protruding far into the camera housing, which would collide with the oscillating mirror. These lenses could therefore only be used with cameras that were equipped with a mirror lock, as the mirror was not allowed to fold back into its original position even after it was triggered, in order to prevent it from being damaged by the lens.
Live preview
With digital SLR cameras, video recordings and live view are only possible with the mirror folded up and locked, with the exception of rare special designs that use two separate sensors.
Sensor cleaning
The sensor cleaning at DSLR -Kameramodellen is a common occasion when the mirror has to be folded up and kept in this position. Most DSLRs have a corresponding selection option for this in the menu. Recordings are not possible in this mode. Since the mirror and the focal plane shutter are usually held in this maintenance position by means of an electromagnetic or electric motor, most cameras only allow this function with freshly charged batteries or when using a power supply unit, as the shutter or other camera parts could be damaged in the event of an unexpected power failure.