Sony translucent mirror technology or Sony mirrorless?

Started Feb 2, 2013 | Discussions thread
heliguy Regular Member • Posts: 410
Re: Sony translucent mirror technology or Sony mirrorless?

Kim Flowers wrote:

Hi, I am trying to choose between the a57 and one of the NEX cameras. Can anyone tell me what advantage the translucent mirror provides when compared to a mirrorless camera, if any? Not sure what it (the translucent mirror) accomplishes. Thanks so much!!

The translucent mirror provides a continuous feed to the autofocus sensors to determine distance between subject and camera. This means the camera has full time autofocus using the phase detection principle. The same autofocus system used by DSLR's in general, but DSLR's only get a signal when the mirror is down to feed both optical viewfinder and the autofocus system (the regular DSLR phase detection AF system thus goes "blind" every time the mirror flips up during exposures, live view and video).

The NEX cameras autofocus using a contrast detection system which is based on (local contrast) information gathered by the imaging sensor. The difference is that this system cannot measure distance but relies on a semi trial-error way of determining where focus is sharpest. This is inherently less capable of following subjects, especially if they move faster and less predictable.

The latest NEX cameras have a hybrid system that combines the above mentioned contrast detection with assistance from phase detection pixels on the imaging sensor itself. Because the phase detection on the imaging sensor relies on individual small pixels, it's not nearly as sensitive and responsive yet as a dedicated phase detection system as found in SLT's. Thus still not comparable when it comes to follow focus with moving objects.

In short you can sum up the differences between the autofocus systems as follows:

  • Contrast and hybrid (the combination) detection autofocus in the NEX is very accurate, but not as suitable for fast and/or unpredictable moving subjects.
  • Phase detection autofocus in SLT cameras is more reliant on a good calibration (which you can fine tune on the A77 and A99, not the other SLT's) but faster and much better suitable for follow focus.

Asside from the above, SLT cameras also have image stabilization built in the camera (sensor shift), which works with every lens attached, where as only a few NEX lenses are stabilized and the cameras themselves do not have stabilization.

Third, there's obviously a difference in size and ergonomics, factors that only you can weigh yourself by trying.

Excellent summary, always wondered @ the differences!

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