I understand that my Canon 450D's (XSi/Kiss X2) passive autofocus system knows a spot in the view is in-focus when its nearby contrast is adequate. Then the camera blinks AF confirm lights to inform me which parts are in-focus (or if the chosen spot is in-focus).
I have few older all-manual lenses, which I use with an adapter. Why the AF confirm lights won't blink when the spot is in-focus while using an all-manual lens with an adapter without any connectors?
I do have an adapter which was marketed as "AF-confirm" and that it has a "chip". With it the camera does blink the AF confirm lights. What I fail to understand is why the connectors are needed? What data the camera needs from the lens? Camera does record some EXIF information when using the "chipped" adapter, but for example the "Lens" field is "1-65536" so it really couldn't be much of an use.