Bulb (photography)

From long-term exposure is spoken in photography from an exposure time of several seconds. Long exposures are used to take pictures even in low light still can or motion sequences demonstrate the technical and artistic area.

In the available light photography long exposures can be avoided by highly sensitive films or image sensors and fast lenses if possible, since usually a tripod is being used. At night photography long exposures are often used, the field of application, however, is universal.

Image effect

Long exposures show a segment of time as we usually can not perceive him. In contrast to " normal" photographs they do not hold a brief moment, they form the motif in a longer process from. Movements are blurred here, they melt away in time.

The approximately two-year exposure times from Potsdamer Platz by Michael Wesely ( see Related links ) show a horizon through the new building through which could be seen even before the development of the place. The sun orbits appear as bright stripes very much to the fore.

Due to the long exposure time, a large motion blur, which can be used for aesthetic results with moving objects (see Light Painting). Moving objects or persons are blurred and can even completely " disappear ," which is used in, for example, architectural shots. In the dark bright objects leave ( eg headlights of vehicles ) light strips. Long-time recording of a night sky ( without the influence of interfering light sources such as street lights ) let the stars look through the earth's rotation, such as lines or circular segments.

Implementation

Most long exposures play in the context of five seconds up to several minutes. The exposure time is set a limit up hardly. Michael Wesely has performed extremely long exposure times of up to 26 months.

A correct exposure at long times and not too dark motif can be achieved by various means:

• Smaller aperture, eg f/16 to 32 ( depending on lens )
• Use of a film having a low light sensitivity, for example, 50 ASA
• Neutral density filter on the lens
• Reduction of ambient light, dusk and night.

Some motifs and design effects, such as light pendant fixture or experiments based on a lomography, can also dispense with the use of the first three agents.

If only one moving object, but not the background be reproduced blurred and hazy, so the camera must be secured to prevent camera shake, for example, by a sturdy tripod. When using a tripod image stabilization systems should be turned off. You can otherwise by " overreaction " again lead to blurred images. For cameras with manual exposure mode or time delay to long exposure times can be set directly.

On most cameras, the function for long-term exposure is marked with a B, which is in Germany for All, in the U.S. for Bulb (English bellows / ball). This is due to that earlier have been remotely controlled cameras with such a bellows device. Most electronically controlled camera, the exposure time is limited by the capacity of the battery, since the keeping open of the closure requires power. Cameras with mechanical shutter allow ( almost ) unlimited exposure times, for cameras without closure, about pinhole cameras, this also applies. If any - - For vibration-free operation of the shutter, a cable release, in more modern cameras a cable release or wireless remote release and mirror lock-up is helpful, alternatively, the delayed self-timer can be used.

In the early days of photography, the long exposure was not a pure design tool, but a necessity. This was due to the low sensitivity of the photographic material and the low intensity of the lenses used. Dailies busier thoroughfares often show no or scheme like blurred people for portraits aids were necessary.

Special

It should be noted that in chemical footage required by the Schwarzschild effect longer exposure times when the meter indicates. This deviation depends on the footage.

In digital cameras, this correction is omitted, it results in a higher noise level of the image sensor, which can be partially offset by certain " denoising ". In modern digital cameras after a picture is taken with the shutter closed as " noise pattern " to the long exposure. This pattern is used to reduce the noise of the recorded image. It should be noted that some cameras record the noise pattern as long as the image and the camera at this time ( for example, when flash photography ) is not ready for use.

Another very effective method, but which can not be applied when there are in the image motion pattern, is the method of multiple shooting. This allows the screen with absolutely identical settings is taken more than once. Since disturbances regarding noise random behavior, they can be eliminated in an image editing program like Photoshop on these images. In the modern, digital photography you call this method also " to stack ". Also, this method is used in the depth of field extension.

Sample Images

10 seconds in an image

Lightning during a thunderstorm (15 seconds)

Waterfall ( 7 seconds)

Multiple short (16 seconds)

A thunderstorm in Liechtenstein (25 seconds)

Evening rush hour in Madrid (30 seconds)

Brandenburg Gate at night (8 seconds)

Fireworks 2009 maximum (20 seconds)

Sparkler ( 46.4 seconds )