Flash like the pros: Many pretty picture has been ruined by the wrong use of a flash unit. It’s about much more than just red eyes on the photographer. The professional photographer We explain what you need to flash – and how to do it right.

The flash unit is probably the most universal light source in photography. Regardless of the power grid, it offers a lot of light in the smallest of spaces, but can do much more than simply compensate for the lack of brightness, and many a special lighting effect is only possible with an external flash unit. Despite the modern camera technology, the use of flash is still problematic. In this chapter, you will learn how to achieve perfect photos with the flash unit.

Technical basics of lightning

A flash makes many a photo only possible, the recording without artificial light would have only blurred or underexposed. Despite great advances in flash and camera technology, the use of a flash unit is still problematic and often does not lead to the desired result.

Even using a digital camera has not changed the basic problems of flash photography. The most common mistakes when using a flash unit are:

  • Red eyes
  • hard shadows
  • a strong drop in brightness that leads to an overexposed foreground on a completely dark background

The optimal exposure of flash photography is not easy even with the digital camera, which has two main reasons:

1. The flash only lights for a fraction of a second.

2. The strong decrease in brightness when using a flash unit is due to the physical basis that the light intensity decreases with the square of the distance. In other words, if an object is twice as far away, only a quarter of the original light is left. In daylight shots, this is hardly noticeable, because the daylight has traveled the very long way from the sun and “a few” meters more or less play virtually no role, so that even large objects are illuminated relatively evenly. The flash unit, on the other hand, is only a few meters away from the subject and the rapid drop in brightness is clearly visible. In practice, this leads to the fact that although the main subject is perfectly illuminated in two meters distance, but all objects that are closer to the flash unit,

For the right use of the flash unit and for optimal exposures in photography with flash, it is therefore important to realize how certain settings affect the photo:

  • The choice of aperture affects both the flash and the ambient light to the same extent.
  • The shutter speed, on the other hand, is always longer than the extremely short duration of the flash and therefore has only an effect on the proportion of ambient light in the overall exposure, the proportion of the flash is not affected.
  • The only way to change the amount of flash light within the total amount of light in the photo is to reduce the flash output.
Long exposure with available daylight with an exposure time of 1 second at aperture 11
Michael Hennemann

Long exposure with available daylight with an exposure time of 1 second at aperture 11

Long exposures with the same settings, but now with a fill flash, which brings more drawing and brilliance in the flowers
Michael Hennemann

Long exposures with the same settings, but now with a fill flash, which brings more drawing and brilliance in the flowers

If the flash setting and aperture remain unchanged but the shutter speed is shortened (in this case to 1/125 s), the proportion of continuous light in the overall exposure decreases.  The flowers in the foreground remain unchanged, but the background sinks in the dark because the amount of light in the flash decreases quadratically with distance
Michael Hennemann

If the flash setting and aperture remain unchanged but the shutter speed is shortened (in this case to 1/125 s), the proportion of continuous light in the overall exposure decreases. The flowers in the foreground remain unchanged, but the background sinks in the dark because the amount of light in the flash decreases quadratically with distance

In a long exposure with synchronization to the first curtain, a moving subject pushes the light trail in front of him, which gives a very unnatural impression
Michael Hennemann

In a long exposure with synchronization to the first curtain, a moving subject pushes the light trail in front of him, which gives a very unnatural impression

When synchronizing to the second shutter curtain, however, the light trail is behind the moving object.
Michael Hennemann

When synchronizing to the second shutter curtain, however, the light trail is behind the moving object.

Modern flash units offer a variety of functions, which you can set partly on the flash, and in part on the digital camera. There are basically three different flash modes:

On the back of the system flash unit, a display informs, among other things, about the selected operating mode and control keys allow various setting options
Michael Hennemann

On the back of the system flash unit, a display informs, among other things, about the selected operating mode and control keys allow various setting options

  • In automatic mode, a sensor on the flash unit detects the amount of light reflected from the subject and turns off the flash when the correct exposure is achieved. When calculating the correct exposure, some settings of the camera are taken into account.
  • When set to Manual, the flash always emits full power (or a specific fraction of it previously set by you). The manual flash control is useful in some special cases such. B. the multiple flashes.
  • In TTL (= “Through the lens”) flash mode, the camera measures the light passing through the lens (both flash and ambient). In analogue cameras, TTL flashing measured the light reflected from the film. Since the sensor of the digital camera (or more precisely, the antialising filter in front of it) has different reflection properties, digital cameras can no longer measure the reflected light in the TTL flash mode. Therefore, the flash fires shortly before the actual recording from a low-power pre-flash, which is measured by the lens. In fractions of seconds, the camera computer makes the necessary settings for the actual exposure and controls the main flash accordingly.

For most photos, the TTL flash mode provides the best results, because its great advantage is that all exposure effects such. As lens properties and even possibly used lens filters are taken into account in the measurement.

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