Module 2F: Types of Flash
F. Types of Flash
When it comes to lighting efficiency, flash photography provides the photographer with a powerful light source with plenty of options for controlling the output and use with modifiers. These can be classified into three primary categories including Speedlights, Monolights, and Power Packs with Flash Heads.
Speedlights
Speedlights are the class of portable strobes that mount onto a camera, usually via a hot shoe. The hot shoe on the camera makes the electrical connection that is required to fire the unit when it is mounted on the camera.
Monolights
Monolights are self-contained flash units that have the power supply built into the unit. They are built to be used with a light stand. They can be powered by batteries or by plugging into them into an AC power outlet, or both.
There is an entire class of monolights that are battery powered which makes them an ideal choice for working outdoors and on location.
Power Packs and Flash Heads
Unlike monolights where the power of the strobe is built into the unit, Power pack systems provide a central hub that supplies power to multiple flash heads simultaneously. Flash heads can easily be connected and disconnected from the hub as desired.
Shutter Speed and Flash
The burst of light from a flash happens very quickly. So quickly, in fact, that the flash of light happens faster than most of the conventional shutter speeds. Because the flash duration is so short, the shutter speed has no bearing on the exposure from the flash. Only the f-stop and ISO have any impact on the exposure from the burst of light from a flash.
For this reason, equivalent exposures are not used with flash exposures. If you want to use a specific f-stop, you will need to ensure that the flash is set to deliver the desired output. For example, if you want to use a shallow depth of field at f2.8, you will have to adjust the output of the flash to fire at f2.8. Conversely, if you want to use f16 to get a large depth of field, you will have to adjust the output of the flash to fire at f16.
When it comes down to flash photography, only the f-stop controls the exposure for the flash. However, the f-stop and the shutter speed still impact the overall exposure of the ambient light that is present during a flash exposure.
Flash Sync
Because the flash fires so quickly, most cameras need to coordinate the timing of the flash firing only after the sensor is completely unobstructed by the camera’s shutter or curtains.
When using any flash system, we need to know the correct flash sync of the camera. This is the fastest shutter speed that can be used and still coordinates the timing of the flash with the shutter and/or curtain in the camera. The sync speed is determined by the manufacturer and model of the camera being used.
Most cameras will sync at 1/125 or 1/250, but it may vary from camera to camera. Be sure to check your camera manual to determine your camera's sync speed.
Flash photography with a shutter speed that is faster than the camera’s designated sync speed will cause the camera to be out of sync.
Out of Sync
Failure to use the correct flash sync may result in a portion of your photograph to be black. This occurs when the flash fires and the curtain mechanism or camera shutter has not had time to fully open and clear the sensor before the flash fires.
When this happens, the flash fires while the curtain blocks a portion of the sensor, so nothing is recorded in that area. This creates the black area on the photograph.
Flash photography can be done with shutter speeds that are slower than the camera’s designated sync speed.
High Speed Sync
Compatible cameras and flashes equipped with High-Speed Sync allow the photographer to take images outside the limitations of the camera’s usual sync speed.
A typical example in which high speed sync might be useful would be in a setting with a bright background and a subject that is considerably less illuminated. In this situation, if we expose for the background, the subject would be too dark. Conversely, if we expose for the subject, the background would be too bright.
When using the High-Speed Sync option, the camera is set to properly expose the background using shutter speeds faster than 1/200. In this mode, the flash will fire several bursts in coordination with the movement of the curtains that open and close during the exposure.
The result is that the ambient light is recorded as usual, but the flash is recorded in different sections on the sensor as it fires multiple times during the exposure.
Because the flash must make multiple bursts during a very fast exposure, it fires at a reduced output each time it fires. This usually means the flash cannot be too far from the subject for it to be effective.