Sony Focus-by-Wire Velocity Sensitive

[Ed_Ingold]

<p>Many have complained that focus-by-wire (FBW) used for manual focus in Sony autofocus lenses is slow and seemingly with annoying lag. That was my experience at first, but I've since purchased and used a Sony 70-200/4 extensively, as well as a borrowed Sony 35/2.8.</p>

<p>Unlike Nikon AF lenses, the focusing ring is not coupled directly to the helix, rather telegraphs signals to the AF motor via the camera electronics. With Nikon lenses (and other SLR AF lenses), the throw is very short with little resistance. We have learned to be gentle when manually focusing these lenses, almost squeezing the ring rather than consciously moving it, for fine control. That method of operation on a Sony FBW lens is sluggish to an extreme. What I found by experimentation is that a short, rapid motion spans a much larger focusing range than a slow precise motion. Used in this way, it is possible to find the focus point quickily, then fine tune it very precisely. It is actually easier to focus too slowly than too quickly, even in the fine-tune mode.</p>

<p>Oddly, this feature is not documented by Sony, nor in any of the many reviews I have read. However it is specifically mentioned by Zeiss in data sheets for the new Batis lenses due for release in July. It is not necessary to use the AF/MAN switch on the lens. Simply move the AF/AES lever near the eyepiece to the AF position and press the center button. When you do that, moving the focusing ring also automatically engages focus magnification (if enabled in the menu).</p>

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