Abbreviation: One Touch FC = "One Touch Focus Clutch Mechanism" (Tokina)

The abbreviation One Touch FC means "One Touch Focus Clutch Mechanism" and is seen on Tokina products.

Explanation from Tokina

A refinement of the focus clutch mechanism has been incorporated in the AT-X 280 AF PRO Nikon and Canon mount, so that now the lens’ focus ring can be snapped back to the manual focus position at any time, from any position. This improvement means it is not necessary to change the AF/MF switch (on the body with Nikon or the lens with Canon) every time the lens is changed from auto focus to manual focus mode.

See examples of effected products

	Tokina AT-X 16-28mm F2.8 PRO FX
	Tokina AT-X Pro 11-16mm F2.8 DX
	Tokina AT-X Pro 35/2.8 DX Macro

See links