Thoughts on the 7D Mark II (or whatever they call it): It appears Canon is putting a lot of effort into dual pixel technology and we’ve heard there is more to come in terms of capabilities with this sensor structure. If we want to make DSLRs better, as far as I’m concerned, one of the last remaining flaws in these cameras is autofocus for stills. Especially with lenses at f2 or wider, focus can often be off. Focus micro-adjust can mostly fix this on cameras that have this ability. I’ve shot with my f1.4 lenses wide-open occasionally and my “hit rate” for proper focus, even though the camera says I was in-focus, is not all that great. This is after I’ve micro-adjusted the lenses to the camera. Auto-focus sensors optimized for f2.8 are just not that accurate with faster lenses.
Let me proposed a way to fix this. We know a camera that knows which of its autofocus points is in-focus, can matched it to a spot on the image sensor. We can also estimate that an exposure sensor, with enough pixels, could keep track of where this point is, even if you recompose before taking the shot. Starting with this, after the shutter bottom in pushed, in single-shot mode the camera would swing the mirror up, then fire the shutter let’s say at the flash-synch speed (~1/200 sec) where the entire sensor is exposed. At this point the dual pixel sensor could fine-tune the focus at the point it knows is the intended focus point. The shutter could then close and reopen again to make the image. Another way to do this is to open the mechanical shutter and fine-tune focus, and then allow an electronic shutter to take the final image, before closing the mechanical shutter. This technique could probably be used at a low-rate continuous shooting mode (eg. 3-5 fps, as I assume the max. 10-12 fps is set more by the mirror mechanism than the mechanical shutter). This technique could only be used with decent ambient light and would not work below a certain illumination. But perhaps flash could be made to work with this technique. With enough light, this technique could allow lenses with teleconverters that produce an effective F-stop higher than f5.6 or f8 to be autofocused. I assume this would be a selectable feature on the camera and not necessarily the default. Just some thoughts on how dual pixel could make DSLRs better.
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