B.I.G. CTCO adapter for Canon FD lens to Canon EF body

A "foreign body to foreign lens" type adapter.

In order to mount/put together a lens and a body with an unequal bayonet or thread, you need a special adapter. It goes without saying that autofocus and aperture won't work, you'll be focusing manually and working with time lapse or in manual mode to get correct exposure metering.

This particular adapter has an optical element in it that provides focusing at infinity. There are also slightly cheaper versions on the market, but these do not provide infinity focusing.

The optical element is adjustable and removable. When you take it out, you can use the adapter normally without focusing at infinity and at the same time use it as a macro ring.