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    • Yes, I agree, mirrorless is the future.

      For the here and now, dSLR technology still wins for AF in lower and lowest light. For sensitivity to subject shapes of any size and direction nothing beats the current best AF technology; Canon's Closed-Loop AF (in certain bodies and certain lens combinations) plus Double-Cross (and iterations and variations of such) Phase-Detect sensors.

      Dual-Pixel (Canon's AF solution for current high-end Live-View and Mirrorless) is currently limited to vertical-edge sensitivity, but Canon has patents which carry that technology forward by sub-dividing each pixel into quarters, bi-horizontal and bi-vertical, which allow a Cross-type Phase Detect (Vertical "and" Horizontal edges detected). By combining these AF arrays at the sub-pixel level, all sorts of AF shapes should be possible (although the AF will still be most sensitive to vertical and horizontal edges).

      Mirrorless technology has no optical viewfinder, only an electronic viewfinder when present. Electronic viewfinders are really just smaller LCD displays, subject to the same delays as larger LCD displays. As the refresh speed increases, the delay from:

      1) Image acquisition on the imager chip
      2) Image processing
      3) Image display on the viewfinder/LCD

      ... cycles does decrease, but there is always a delay before the operator sees the scene action and can respond accordingly.

      Yes, a dSLR has a blackout period between cycles, but you do see the action unfold at approximately 186,000 Miles-per-second (speed-of-light) when the mirror is down. The short bursts many sports photographers use, for instance, are not a problem for dSLR systems.

      A prediction of certainty is that soon mirrorless cameras will be able to buffer a few frames continuously, so that cameras will be able to record frames from before the user pressing the shutter button. (Some video cameras/camcorders already do this, but I don't know of any still cameras with this capability, yet.)

      To summarize, there's a reason you still see a plethora of professional photographers using dSLRs for most events requiring best system responsiveness, and especially in lower and lowest light; dSLRs still generally beat mirrorless systems for AF acquisition and for overall system responsiveness.

      In good light, mirrorless are tantalizingly good for AF acquisition, so the situation will change, but I still greatly prefer, and overall recommend, dSLR systems for still image acquisition in all lighting conditions.