Focus By Wire?

Discussion in 'Native Lenses' started by tjdean01, Oct 9, 2013.

  1. tjdean01

    tjdean01 Mu-43 Top Veteran

    Feb 20, 2013
    Sometimes I want to use manual focus on my native, autofocus lenses (14, 20, 14-42, 40-150) but I don't because, as I understand it, when I move the ring, it operates a wire (?) which then moves the motor which in turn moves the glass?

    The exception is the Sigma 30. When I put that on manual it's very good and easy to focus and isn't jumpy like the rest of them. Why is this one different?

    Also, the 12mm f2 has a little ring to click it into MF mode. Is that REAL MF or focus by wire? I heard it's ALMOST like MF but not really and is not fly by wire. I'm confused. It looks like the 12-40 is going to have the same thing.

  2. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    Focus by wire is kind of like a power zoom on a lens. The focus is not physically coupled to a focusing cam. Rather turning the zoom barrel activates a switch which strts a little motor which moves the focusing group.

    As with anything focus by wire can vary in quality. In the 12mm you have a good implementation (that costs more to make) so it feels more like a traditional mechanical focus. The cheaper stuff has weaker motors and longer electronic lag which means it sucks.

    I would expect the 12-40 will be better than the cheap stuff but still focus by wire. I'm happy enough with what the Panasonic 12-35 does and I susupect the 12-40 will be quite similar.

  3. tjdean01

    tjdean01 Mu-43 Top Veteran

    Feb 20, 2013
    Cool. Thanks for that. No idea why the Sigma works so well? It does have something ratting around in it when it's powered off. Maybe that has something to do with it?

    There's a lot of talk on here recently about the 12-35 and how it compares to primes and to the 12-40. I too am thinking about the 12-35 but I would miss the MF.
  4. Andym72

    Andym72 Mu-43 Veteran

    Mar 4, 2013
    Reading, UK
    "By Wire" just means there is an electrical/electronic connection between a control and what it moves, as opposed to a mechanical or hydraulic connection.

    The term comes from the aircraft industry, where the hydraulic direct connection between the stick and wing flaps have been replaced by sensors in the stick that generate digital pulses, get sent to a computer, and then the computer actuates motors in the wing. This is called Fly By Wire.

    All AF lenses for m43 are Focus By Wire, yes, even the 12mm and 12-40mm. The focus ring has sensor underneath it that generate digital pulses, these get sent to the camera body processor, and then it sends the command to focus to the lens motor, in the same way it sends focus commands during autofocus.

    The pull back focus ring (Snap Focus) is still Focus By Wire but it changes the behaviour a little. You get "end stops", where the ring won't turn anymore when you reach the limits, and the focus movement become constant rate calibrated to the focal distance markers. It's really not any more usable for MF than the "standard" Focus By Wire ring on other lenses, it just has a different "feel" (it feels closer to mechanically linked focus systems so might appeal more to people coming to m43 from another older system). Since you don't have any of the lenses with Snap Focus, how can you miss something you don't have?
  5. chipbutty

    chipbutty Mu-43 Top Veteran

    I mentioned the excellent manual focussing quality of the Sigma in another thread. I have no idea why it's so good compared to all other m43 lenses I've tried. I wish they all worked so well.
  6. MAubrey

    MAubrey Photographer

    Jul 9, 2012
    Bellingham, WA
    Mike Aubrey
    Have you tried the 75mm f/1.8? It's just about perfect.
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