Lightning methods
Under fill flash comprises various procedures when using the flash light in the photograph . The flash methods differ:
- in the task of the flash as main, fill or auxiliary light
- at the time the light is emitted within the exposure process or before
- in the manner of lightning (a pulse or strobe)
- in the direction of emission of the light (direct or indirect)
- in the type and position of the lightning bolt
Methods
Flash on the first shutter curtain
This is the oldest flash method and works in principle with any combination of flash unit and camera , provided that there is a possibility of flash synchronization at all . The flash fires immediately after the shutter opens . The amount of light is measured either by the camera or by a sensor integrated in the flash unit, and the flash is switched off after sufficient exposure . The technology can also be used with unregulated flash units. The lightning time of the flash is usually much shorter than the open time of the shutter.
With fast moving subjects and significant ambient light, unnatural-looking motion blurring often occurs , since the subject sharply outlined by the flash is, so to speak, at the beginning of the movement. A car driving from left to right at night appears on the left in the picture, from its headlights a trail of light leads to the right into what appears to be nothing.
Flash on the second shutter curtain (rear sync)
After opening the shutter , the existing light is first captured. The flash is only fired shortly before the end of the exposure time . This technology can only be used reliably with coordinated system flashes or flashes built into the camera, since the control electronics must take into account the maximum lighting time of the flash unit (see: long-term synchronization ). This technique usually results in a more natural representation of moving subjects. In the scenario used as an example above, when the lightning strikes the second shutter curtain, a spotlight trail is created that begins on the left in the picture and ends on the right with the car.
Pre-flash
In photography, a pre-flash is any ignition of a flash unit before taking a picture. Such a pre-flash can fulfill different tasks:
Red-eye reduction
The red-eye effect is caused by the reflection of the flash on the retina. This effect occurs particularly in dim and dark surroundings when the pupils are wide open and the lightning strikes the eye head-on. A pre-flash should reduce the red-eye effect. The so-called red-eye circuit in the flash fires one or more flashes in close succession before the actual picture is taken. The previously ignited flash light constricts the pupils of the photographed person or animal, and the red eyes become much less noticeable.
The use of this flash function has many disadvantages. The person being portrayed becomes attentive or even irritated, making a snapshot impossible. There is also a noticeable delay between triggering and the moment the main flash is triggered. The photographer is no longer able to determine the exact moment of the picture. The facial expression of the person portrayed changes, in the most unfortunate case the pre-flashes lead to reflexive closing of the eyelids. Experienced photographers therefore keep their hands off this setting; they avoid the red-eye effect by using external flashes, which are ideally attached to a rail on the side of the optical axis, indirect flashing or the use of "umbrellas" or bouncers (see below ). With the help of electronic image processing , red eyes can also be changed retrospectively by digital retouching .
AF-assist illuminator
(see also detailed section AF auxiliary light )
The pre-flash can also be used as an auxiliary light for the autofocus to focus a subject in difficult lighting conditions, if the camera does not have an additional auxiliary lamp or the auxiliary light measurement of an external system flash unit is not available. For this purpose, relatively weak stroboscopic flashes are ignited during the focusing process, which briefly brighten the subject. Disadvantages of this method are the relatively high power consumption and the irritation of the motif and the audience due to the long, glaring strobe bursts.
Many modern flash models to attach use a red auxiliary light, which is therefore not so bright. A cross-like pattern is often projected to provide structure for the autofocus.
TTL pre-flash (measuring flash)
(See also TTL flash measurement )
With modern cameras and flash units, the pre- flash is used in the TTL measurement process to better coordinate the exposure (ratio between flash and ambient light).
This type of pre-flash is triggered so shortly before the actual flash that it is often not even noticed. This TTL measuring method using pre-flash became necessary with the introduction of digital cameras. With the previous TTL measurement methods, the flash light reflected from the matt film surface was measured during the exposure. The sensors of the digital cameras have very unfavorable reflective properties due to their reflective surface, so that a measurement can be very imprecise depending on the subject. During the pre-flash measurement, the flash light is usually measured by the continuous light exposure meters. This flash method is named differently by the camera manufacturers, Canon calls it E-TTL, Nikon i- or D-TTL, Pentax P-TTL. An exotic variant measures the light reflected from the closed shutter curtain .
In portrait photography and animal photography , however, as with red eye reduction, undesirable reflexive closing of the eyelids can occur. This can only be dealt with by switching off the TTL automatic, but this is not possible with all flash units and cameras .
In the case of servo flash triggers of multiple flash systems (see Unleashed flash ), it is important to ensure that the pre-flash is switched off if not all devices used are set to it. If controlled flashes are already triggered by the pre-flash (e.g. studio flashes that are triggered by a photo cell) and thus no longer react to the actual picture, the image would also be incorrectly exposed due to the previous flash exposure measurement, because the triggered studio flash is included in the measured value taken into consideration.
Slow, fill, or slow flash
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This flash method can be used with the synchronization on the first shutter curtain or on the second shutter curtain. The exposure is determined by the given ambient light, the flash usually only serves as a brightener and illuminates the main subject, thereby strong light-dark contrasts are softened, and there is better shadow detail when taking the picture.
Fill-flash is useful when there is a strong, direct light source, such as strong sunlight, because it creates heavy shadows , and when it is backlit it prevents the foreground from becoming too dark. In gray and hazy weather, he adds the necessary light to the foreground so that the colors appear clearer and purer.
However, it can also be used to freeze movement in order to reduce or completely prevent the strong blurring of moving subjects that occurs with long exposure times. The flash unit is often used with reduced power or brightness so that the available light comes into its own. On the other hand, in strong sunlight, you may need a particularly powerful flash to have any effect at all.
In the case of indirect flash (e.g. over the ceiling), unsightly shadows also arise. Some flash units therefore have an additional fill-in reflector that deflects part of the light from the flash unit or a second small flash tube that flashes directly when the main flash z. B. is directed towards the ceiling.
Modern automatic cameras detect usually automatically the need of whitening with flash and fire a switched flash automatically, which then typically one to -1 to -2 EV ( Exposure Value = light value , exposure value ignites) than in the general brightness reduced flash. In the case of manual control, a balanced ratio between daylight and flash light should be sought. First attempts should start with a flash intensity of −1 EV.
The shortest possible flash sync time is necessary for fill-in flash in order not to be restricted in the choice of the f-number. Ideally, a modern flash unit with FP synchronization is available. A long sync time forces you to stop down in bright light conditions, which in turn has a negative effect on the flash range .
Strobe flash
During the exposure time either a flash is ignited several times or a stroboscope is used. A moving object is exposed in different phases. If the environment or the background is dark and only the object is illuminated, this can also be captured in images, similar to the method for short-term synchronization . Depending on the frequency and speed of the object, the individual phase images are closer or further apart. This method is suitable, for example, for motion, acceleration and deformation analyzes.
Indirect flash
The Bouncing (correct: bounce flash or bouncing flash , that is "rebounding" or "bouncing flash") is a term from the photograph and said in English in general a bounce flash as against the ceiling (or a bright surface or Aufhellschirm ), which usually leads to a much more even and softer illumination and largely avoids or at least softens hard shadows . In addition, unwanted reflections and highlights, for example on eyeglass lenses, are avoided.
However, a certain basic performance of the flash unit is an absolute prerequisite (sufficiently high guide number ), since a considerable part of the amount of light can be lost due to the not insignificantly longer path of the light and its scattering on the reflective surface, which may be quite far away.
When taking pictures of people, pointing the flash at the ceiling often creates unsightly shadows under the chin or in the eyes. The indirect flash is therefore often used together with a fill flash or reflector (see above / below)
Bouncer
Instead of flashing a wall or ceiling, you can also use bouncers . In photography, this is used to describe a diffuse (opaque) plug-in attachment for flash units . This fans out the flash so that it covers a larger area and the light is softer.
Reflective surfaces that can be attached or glued directly to the flash unit at an angle are also called bouncers . Something experienced hobbyists can of course make them themselves. Here and there you will also find the term bounceboard (which actually means trampoline ), often foldable and optionally tinted (gold foil) light-up umbrellas of different sizes (up to square meters!), Which are mainly used in daylight photography or outdoors to Example of directing sunlight onto the subject - or parts of it.
For devices without a tiltable and / or swiveling flash, there are flash tilters . However, the possibility of automatic flashing is usually not available, in which the device calculates the required amount of light itself ( see computer flash ). This is due to the fact that in this case the measuring cell no longer points at the subject, but in the direction of the reflective surface (e.g. the ceiling), which would result in drastic underexposure .
Combinations of direct and indirect flashes
Some electronic flash units allow direct and indirect flashing at the same time because, in addition to the swiveling main flash tube, they also have a mostly rigid fill-in flash; By combining both methods, even difficult lighting requirements can be met. For example, the central motif - for example a person in the foreground - is illuminated with high contrast, while the background is adjusted to its brightness by the indirect main flash and does not "sink into" the dark, as is often seen in amateur photos.
Of course, this can also be achieved by using several flash units, whereby the possibilities increase even further: for example a smaller direct flash, an indirect main flash for the overall illumination of the scene and, if necessary, a spot flash to highlight a certain part of the subject, possibly even differentiated in color.
Instead of the additional fill-in flash, some flash units have a small reflector that deflects part of the flash light forward. If your own flash unit does not have such a reflector, you can simply improvise it by attaching an approx. 1 cm wide strip of aluminum paper behind the reflector so that it guides a part of the indirectly emitted light forward.
Lightning unleashed
(see main article Unleashed Lightning )
Usually flash units are attached close to or on the camera or are integrated into the camera. Due to the front lighting, motifs usually appear flat and unnatural. In addition, parts of the subject close up are often overexposed, more distant parts sink into the shadows, and the notorious red-eye effect occurs. If you increase the distance between the camera and the flash unit, you can easily achieve a more natural lighting. By using several flash units with or without additional reflectors, the effort can be increased as required, but perfect results are also possible that cannot be seen from the flash technology.
When the flash is unleashed, the remote flash units are usually no longer triggered by control cables, which are unwieldy and represent tripping hazards. Instead, daughter flashes are used, which are triggered, for example, by the master flash connected to the camera . The use of a flash exposure meter is very helpful for targeted lighting with multiple flash units, and is practically indispensable for studio flash units .
Open flash
Open flash refers to the - usually multiple - manual triggering of a flash unit with the camera (tripod) fixed and the camera shutter held open. This technology offers two benefits: The maximum output of a flash unit can be multiplied by repeated triggering: the number of flash releases must be doubled for each f-stop of brightness gain. Second, the position, direction and power of the flash can be changed between releases in order to simulate the effect of several light sources and to achieve accentuated or shadow-free illumination.
Due to the time required, the open flash technique is only suitable for static subjects. Since the camera shutter remains open between the flash releases and the photographer sometimes has to move through the field of view, the lowest possible ambient light is advantageous. The flash unit used must have a manual trigger option and, if possible, a power control that is independent of the TTL control of the camera.
The open flash technique is particularly suitable for illuminating spacious, angled, lightless surroundings with minimal resources and is therefore a typical technique, for example in cave photography. In studio photography, the open flash technique is used when the aperture has been stopped down to achieve the greatest possible depth of field so that the required amount of light exceeds the output of the flash system.
literature
- Jürgen Philipp: Lightning practice. digital / analog. Lighting basics. vfv Verlag für Foto, Film u. Video, Gilching 2002, ISBN 3-88955-132-7 .
Web links
- Blitztechniken , Foto-net.de
- Jürgen Rautenberg, Indirekt Blitzen , Digitalkamera.de, December 16, 2002
- Dirk Baumbach, cross-pole flashes with polarized light in practice