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Sony A7R II + Sony G Master Lenses: Major Focusing Bug?

See my Sony mirrorless wishlist at B&H Photo.

Sony A7R II

Update: see outdoor shooting results.

In my recent coverage of focusing, I commented on how the Sony A7R II with firmware 3.1 never opens the lens diaphragm to focus, which is a major operational flaw; it’s just not at all likely to center the zone of focus on the target consistently or reliably when stopped down past a certain point*.

*This is easily checked even without taking a picture: set the lens to f/8 or so, verify that the camera does not open the diaphragm when focusing, focus. Switch to manual focus, then open the lens to f/1.4, zoom to 12.5X, observe the blur. The amount may vary from a just a little blur to strong blur and may also depend on subject matter or lighting, but the point is the peak focus does not hit the target and the zone of sharp focus (depth of field) will be displaced from where it was intended, and may even damage sharpness where intended.

Several readers emailed to say that the A7R II did in fact open the aperture when focusing. But they tested with lenses like the Sony 55 1/8, Sony 35/1.4 and Zeiss Batis. As it turns out, they were right; we are all correct, as I investigated and determined the following:

  • With both the Sony GM lenses (85/1.4 GM and 24-70/2.8 GM), Sony A7R II does NOT open the lens diaphragm to focus, at least not under reasonably bright to somewhat dim conditions (checked over 3 different days). Setting Effect = On or Off has no effect on the behavior.
  • With Zeiss Batis 85mm f/1.8, the Sony A7R II opens up the lens diaphragm to focus, every time and regardless of shooting aperture. It’s too quick to see if it opens fully, but it definitely goes to at least f/2 or brighter.

In other words, focusing appears to be a BUG with the Sony A7R II and Sony GM lenses. Even if one rejects that idea and insists this “working as designed”, it is a fatal flaw in accuracy—nothing alters the problematic focusing errors.

Presumably it happens with the other Sony mirrorless full-frame cameras, but I cannot confirm as I don’t have any other camera bodies.

This is not a big deal when shooting at f/4 or so, right? Unfortunately, no dice:

Sony 85mm f/1.4 GM: Focus Accuracy at f/1.4 and f/4 (Lens Align Target)

Other recent autofocus coverage:

Target for this test was the Michael Tapes Lens Align target.

Out of focus at f/4
f4 @ 1/5 sec, ISO 100; 2016-04-19 16:57:06
Sony A7R II + Sony FE 85mm f/1.4 GM

[low-res image for bot]
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