The Bower SFD14S Sony Ringlight Flash for Sony Alpha DSLR cameras is a circular light source which delivers, evenly balanced, shadowless lighting ideal for macro, portraits without red eye, products, medical or technical applications. It has a Guide Number of 46' (14 m) at ISO 100 and features full automatic TTL flash exposure control. When shooting at extremely short distances, relatively minor movement of lighting and subject results in relatively large changes of exposure. TTL metering eliminates the need for lengthy calculations of exposure, because the inherent loss of light at macro distances can automatically be calculated. The ringlight attaches to directly to a lens with a 52mm filter size and by using the included adapter rings (55mm, 58mm, 62mm, & 67mm) it can fit a wide variety of other lenses.