Auto-lock Accessory Shoe

iISO (intelligent ISO) flash shoe (aka "reversed" hotshoe) is the unofficial name for the proprietary accessory flash attachment and control interface used on Minolta cameras since the i-series introduced in 1988, and subsequently Konica Minolta and later Sony α DSLRs and NEX-7 up to 2012. Sony called it the Auto-lock Accessory Shoe (AAS). In order to speed up and enhance attachment, detachment and latching, it departs from the conventional circa-1913 mechanical design that is now standardized as ISO 518:2006 and used by other camera systems, including Canon, Nikon, Pentax, Olympus, and Leica.

The mechanical design of the accessory shoe now common on most cameras dates back to 1913, when Oskar Barnack, the inventor of the Leica, devised it for attaching an accessory viewfinder. By 1940's, with the addition of the central contact, the design became commonly used for attaching and triggering accessory flashes and known as the "hot-shoe". Prior to 1988, Minolta has used that familiar, common hot-shoe design, adding, just like the other makers, its own proprietary contacts for enhanced control.

In 1988, Minolta introduced the iISO flash shoe in its new i series of cameras. Reportedly conceived with the input from Herbert Keppler in 1987, the new Minolta patented design featured a push-button latching mechanism, for the purpose of easier and faster flash attachment and removal and a more secure hold.

On 12 September 2012, Sony introduced a new 21+3-pin metal-based hotshoe with mechanical quick locking mechanism, called Multi Interface Shoe. At first sight it resembles a standard ISO 518 hotshoe with just the middle contact and chassis and without any vendor-specific extra contacts, but additional contacts are hidden under the front of the hotshoe. The new hotshoe is mechanically incompatible with the iISO hotshoe, but electrically backwards compatible. The first cameras to use the new hotshoe are the SLT-A99, NEX-6, NEX-VG900, NEX-VG30 and DSC-RX1. An ADP-MAA adapter to the iISO flash shoe is however provided with the Sony SLT-A99, and the newest flash Sony HVL-F60M, which uses the new hotshoe comes with a reverse adapter ADP-AMA for older Sony and Minolta cameras.

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Wikipedia