The LEICA SF 24D electronic flash unit is designed to be compact and also to provide the maximum distance between the flash reflector and the camera lens, which minimizes the risk of red eye when photographing people and animals. With the LEICA M7 and the LEICA M6 TTL the light output is controlled by its TTL flash exposure meter; with other Leica M models it is controlled by the automatic flash itself. In automatic mode, six automatic flash apertures 2.0/2.8/4.0/5.6/8/11 are available. An override switch allows the exposure to be varied by plus/minus three stops. All settings and other information are legibly displayed on the LEICA SF 24D's illuminated LCD. These include an exposure confirmation indication and flash ready light which are simultaneuously displayed in the viewfinder of the LEICA M7 and LEICA M6 TTL.
The ISO film speed range of the LEICA SF 24D extends from ISO 12 to ISO 3600 in M/TTL range and from ISO 25 to ISO 800 in A mode. The illumination angle corresponds to a focal length range of 35 to 85 mm, and can be extended by means of two supplied diffusers, enabling flash exposure with wide-angle lenses down to 24 mm and telephoto lenses up to 135 mm focal length respectively. Power is supplied by two 3 Volt 123 A lithium batteries, permitting rapid recycling times.