Electronic front-curtain shutter
As well as its high pixel count and 60fps 1080 output, the latest EXMOR CMOS sensor also has the ability to act as the first curtain of the shutter. It's something we've seen on Canon DSLRs dating back to the EOS 40D - the idea that you start with the physical shutter fully open, and begin the exposure by activating the sensor electronically, one line at a time. The exposure is then ended when the physical shutter travels down across the sensor, blocking off the light. The advantage of such a system is that you don't need to cock the shutter or wait for it to mechanically trigger, which improves its response time.
|This video shows the NEX-7's shutter's behavior with electronic first curtain shutter turned off, then turned on. There are four exposures in total, two taken in each shutter mode. (The AF illuminator lights briefly for each exposure because they're triggered using the IR remote control.)|
The video above demonstrates the difference as you experience it. With the electronic first curtain shutter turned off, you hear the shutter make two movements, and with it turned on, the shutter only makes one movement, to end the exposure. (Note that the menu setting for this - 'Front Curtain Shutter' - is ambiguously named, although the Help Guide display explains it means electronic, not mechanical.)
In our shooting, we see no reason not to keep Front Curtain Shutter enabled at all times. It makes no discernible difference to the image quality, and we prefer the more responsive feel of the single shutter movement. It also provides a more fluid Live View output in Continuous Shooting mode, and reduces the camera's operational noise. What's not to like?
Object Tracking AF
Like other recent Sonys, the NEX-7 gets an object-tracking AF option that's designed to maintain focus on a subject as it moves across the frame. It's enabled in the camera menu, and then co-opts the lower soft key to engage and disengage the feature (overriding any custom option you may have set).
|If Tracking AF is enabled then the lower soft-key is used to control the feature. This will override any function you've previously assigned to it, until you turn tracking off again.|
|Pressing the lower soft key brings up this activation screen. Pressing the 'OK' button selects the object in the center of the frame for tracking, based upon its colour.|
|The target then dances around the screen, attempting to track the subject (but often lagging just a little behind).|
In use, Object Tracking AF is (usually) capable of following a subject around the frame, assuming that it is of a significantly different color/tonal makeup to the background, but it isn't capable of keeping track of fast or erratic subjects. Because it works by colour, it's also easily quite confused, and prone to jumping from your actual target to another area of the scene that's the same colour. You can enable object tracking in the NEX-7's 10fps Speed Priority Continuous mode, but note that the focus is necessarily locked across all frames in a burst.
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