MODES FLASH

When operating your hotshoe flash in manual mode, you are basically setting the power of the flash. Most flash units allow you to decided whether to use the maximum or the minimum power it can supply along with steps in between.

Like camera stops, flashes also have stops. These are referred to as flash power, and are measured in fractional increments: 1 (or full) » 1/2 » 1/4 » 1/8 » 1/16 » 1/32 » 1/64, etc. Practically named: Full power, half-power, quarter-power, etc.

Moving one step along this scale (from full power to half-power, or from half-power to quarter-power) is one stop difference. The same change in exposure as adjusting your shutter speed or aperture one stop.

Depending on your particular hotshoe flash model or brand, half or even third-stop power increments might be possible, ust like in-between shutter speed and aperture adjustments. On some flashes, the power can be set directly from the flash and is indicated on the flash LCD screen.

Other flashes (especially the smaller ones with no LCD screen on the back), can only be set through the camera’s menu, or are completely controlled by sensors in the flash. Getting a flash that is compatible with your camera, can make your life a lot easier. Not only is there added convenience, but you’ll also enjoy extended functionality.

When changing the flash power, it’s important to remember that you are not actually altering the amount of light a flash emits. The light burst a flash fires is constant. When reducing your flash power, you are actually just changing the duration of time of that bursts light the flash emits. So, increasing your flash’s power increases means you’re making the flash stay lit just a bit longer.

Another fact is that the amount of light a flash can burst at full power differs from one model or brand to another, and the range of power settings between full power and minimum power differs as well. For example the Canon 580 EX is more powerful than the Canon 430 EX at full power, and it offers a range of power settings that go from full power all the way down to 1/128, while the Canon 430 EX can only go as low as 1/64.

For Canon flashes, E-TTL stands for “evaluative through the lens” metering. When you set your flash to ETTL mode, the flash actually emits light prior to the actual flash firing that is used for registering the exposure. This first light is known as the pre-flash. It then measures the amount of light returned through the lens and compares it with the original amount of light emitted, taking into account the distance between the camera and the photographed subject. Based on those facts, it then calculates the power the flash needs to be set at in order to register an appropriate exposure.

The following images show two different flash settings: In the first image, the flash is set to manual mode at 1/2 power. In the second image, the flash is set to ETTL mode, meaning that the camera will set the flash power automatically according to the framed scene.

Remember, when your flash is set to manual mode you are the one in charge. Meaning you set the flash power and it stays the same from one shot to the next until you re-set it once again to a different power. In TTL mode, your camera works with the flash unit to determine the power needed for a specific scene, and that power does change from one shot to another if necessary. So if the scene changes, the distance to the subject changes, or the available lighting conditions change, a flash in this mode will detect it.