Intelligent AF with a 360k-pixel RGB+IR metering sensor
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Intelligent AF with a 360k-pixel RGB+IR metering sensor

The metering sensor on the 1D X II has experienced a significant increase in resolution. With 360,000 RGB+IR pixels, it's the highest resolution metering sensor we've ever seen. This should lead to accurate metering, and also enables the camera's anti-flicker shooting feature, which delays the shutter firing so that it syncs-up with the brightest moments of the fluctuations that occur with some artificial lighting. 

But the implications of a high resolution metering sensor are most exciting for autofocus. Why? Think of the metering sensor as a low resolution image sensor that can be used to find faces and recognize objects so it can tell the AF system which points to use to follow them (something Canon refers to iTR, and we generally refer to as subject tracking). The main image sensors of DSLRs can't be used to do this (as they can on mirrorless cameras), because they are blocked by the reflex mirror between exposures. However, the metering sensor, embedded in the viewfinder hump, can see the scene in front of the lens whenever the mirror is down. This has prompted the use of increasingly high resolution sensors to provide the cameras with scene and subject awareness. For example, Nikon announced a 180,000-pixel RGB metering sensor in their recent D5/500 announcements (we analyzed its implications here).

So how does it work? Our initial impressions are that subject tracking remains a bit erratic and highly dependent on your shooting scenario - in other words, on the face of it, not as versatile as Nikon's class-leading 3D tracking. While we'd expect it to remain very good at following subjects well-isolated in depth (typically distant subjects shot with telephoto lenses, such as birds), it doesn't appear to be quite accurate enough to track, say, the eye of a face.

We were somewhat surprised by this, given the pinpoint precision Nikon 3D tracking is capable of with a far lower resolution 91,000-pixel RGB metering sensor, and given the accuracy with which the 1D X II itself tended to focus on eyes of faces in One-Shot AF (with 61-point Auto AF). Our guess is that when it comes to iTR, Canon continues to rely heavily on distance information to subject track, which may serve it well for birds-in-flight, distant wildlife, and sports photography, but is known to have its limitations.

In other words, it's not just about how many pixels your metering sensor has, but how you use them. It should be noted though that these impressions are based on limited use of a pre-production camera, so we're not drawing any definitive conclusions at this stage. And at the end of the day, that the camera can focus or subject track at all at 14 fps is nothing short of impressive.