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AF Micro Adj. 301

6.28 AF MICRO ADJ.

Menu Position MENU  6  AF Micro Adjust

What it Does Invokes a feature which can correct for focusing accuracy
when using certain lenses

Recommended Setting n/a

One of the things that has been plaguing Autofocus Cameras (from all
manufacturers) for over three decades has been a phenomenon commonly
called “Backfocus” – it refers to a scenario where a lens-body combination
will autofocus inaccurately – typically a centimeter or two behind or in
front of where the camera ought to be focused. If you’re doing critical
work on your camera, a Backfocus (BF) or Frontfocus (FF) issue can really
ruin a shot for you.

What causes this is a little difficult to explain – it’s not just the body and
it’s not just the lens, but the two of them each might be just enough out of
tolerance to produce a consistent focusing error when used together. If you
wanted to fix this in the olden days you’d have to send both the camera and
lens back to the manufacturer so they could be calibrated together. While
that may have worked, it was time consuming and expensive and often the
problem would be fixed with the lens you sent in but then it would start to
happen on other, previously accurately-focusing lenses.

Over the years the incidence of the problem has been reduced due to better
manufacturing and quality control methods, but still Sony has taken a very
bold step by including this feature, which publicly acknowledges the
existence of the problem. Basically, every time you mount a lens, you can
test for the focusing accuracy yourself and then dial in a correction via this
feature. Whenever you put that lens back on, the camera recalls the AF
correction amount you dialed in for that lens. The camera can remember
correction values for up to 30 different lenses.