Map AF-ON button to Shutter-half-press (50D etc)

Started by pulsar124, May 04, 2013, 04:37:54 PM

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I always found it very annoying that the most accurate (albeit slow) way to focus on my 50D  - using LiveView AF - can only be engaged by pressing the AF-ON button at the back of the camera. This pretty much fails when you try to do it with either long telephoto lenses (>100mm) or using macro lenses - even with a sturdy tripod, the camera shakes so much when you are pressing the AF-ON button that the focus is often not accurate. E.g., when using the new feature of Magic Lantern - dot-tune lens calibration - the very crucial first step (putting lens in exact focus) - fails for me with my 135mm and 200mm lenses, because of too much shaking.

Ideally, I'd like to be able to trigger LiveView AF using my remote shutter control, but it only works with the phase-detect AF, not with Live View AF. Apparently, many Canon cameras suffer from this deficiency: . For 50D at least there is one option - to tether camera to a laptop with Canon remote shooting software (but that defeats the purpose for using ML), but apparently even this option is not available for other cameras (Rebels).

Is it possible for ML to map AF-ON button to the half-press shutter button? That would make it possible to do LiveView AF using remote shutter control.


Another solution for the same problem - perhaps it is easier to implement? Instead of remapping any buttons, a new feature 'delayed LiveView AF' would achieve the same thing. Specifically, if there were a ML option which would introduce a delay between the moment the AF-ON button is pressed and LiveView AF action then one could achieve very accurate contrast detect AF even with telephoto lenses (no camera shaking). For this to work, the AF would have to run on its own (not as long as AF-ON is pressed, as it is now), until perfect focus is achieved, or until it times out.