Question: is it possible to have something like a focus trap, that shoots whenever the AF light lights up?
People on this German forum suggested taping a contact on the lens body, which will result in the camera shooting if the trigger is pushed halfway and the camera gets an "in-focus" signal:
http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=auto&tl=en&u=http%3A%2F%2Fwww.dslr-forum.de%2Fshowthread.php%3Ft%3D165289%26highlight%3Dfokusfalle%26page%3D4
Also, is it possible to trigger the "aperture preview" by software? If yes, a function that triggers that button and holds it would be nice. The reason is that I have spacer rings for my 400d to use my standard lenses as macro lenses. This works quite well but I have to preselect the aperture via press and hold "aperture preview", unscrew the objective while holding the button, mount spacer rings, mount objective. It were better if the aperture preview could be locked so it gets more comfortable.
Cheers,
christian