LED flash (digital camera)
Digital cameras, cell phones and smartphones have a camera flash to support digital photography, providing better illumination for photography and for shooting in the dark. Camera flashes work with white LEDs(WLED) with Ultra High Brightness (UHB) and high luminous efficiency, which is obtained by discharging a capacitor for the power LED or derived directly from the battery voltage.
Compared to classic flash units, power LEDs operate with a lower supply voltage of about 4 V and the power LED can be operated continuously during video recording. LED strobes require a current of about 1 A during short-time discharge. Depending on the color temperature of the WLED, a small amount of color correction may be required. The power of the flash is indicated in the flash guide number.
LED Flashs are hidden behind a small recess on the front of the mobile device and are synchronized during shooting. To increase the light intensity, some manufacturers work with inert gases that support light-emitting diodes with low luminous efficacy. The combination of light emitting diode and xenon flash also has the advantage that the xenon flash is shorter than the LED flash and also freezes fast motion changes.
The different modes for LED flashes
There are different modes for flash control of the camera flash. The standard mode is the TTL mode, Through the Lens (TTL), where the light is controlled by the camera lens. It provides perfect image illumination and is synchronized with the opening of the camera shutter. The intensity of the LED flash is controlled by the amount of light emitted via sensors so that the image is not underexposed or overexposed.
Another mode is the red-eye mode. In this mode, a short pulse of light is emitted before the actual photograph is taken so that the pupils of the people being photographed constrict and the flash does not reflect back from the retina and thus become visible in the photo. Another mode is rear curtain sync, which fires late to freeze the front of a moving subject. In this mode, a slight blur remains at the back, and front curtain sync does the opposite.