Olympus about to surpass DSLR focus speed/accuracy?

Discussion in 'Digital Photography' started by RichA, Jun 15, 2011.

  1. RichA

    RichA Guest

    RichA, Jun 15, 2011
    #1
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  2. On Jun 15, 8:31 am, RichA <> wrote:
    > I'll believe it when I see it.
    >
    > http://www.43rumors.com/ft5-olympus-reinvents-the-af-system-pen-autof...


    It sounds like they've changed something in the lenses
    to help. If it's just a way to drive the elements around
    more efficiently, it could also be applied to phase-
    detect AF, and would presumably give a similar
    improvement in performance.

    I hope it's a lot more than that; re-buying lenses isn't
    high on my list of pleasant ways to spend my money.
     
    David Dyer-Bennet, Jun 15, 2011
    #2
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  3. RichA

    Bruce Guest

    RichA <> wrote:
    >I'll believe it when I see it.
    >http://www.43rumors.com/ft5-olympus...as-and-faster-than-most-canon-dslr-autofocus/



    Olympus hasn't "invented" anything here. The new AF system is the
    same one that Panasonic and Ricoh have licensed. It represents a
    major step change in the speed of contrast-detect AF systems.

    The Panasonic GH2 and G3 have very fast and accurate AF when used on
    stationary or slow-moving subjects. We have found that their AF is
    less decisive when faced with subjects that move more quickly, such as
    vehicles and children. For fast moving subjects, a DSLR is still a
    better choice.

    However, one thing that the new contrast-detect system offers is
    outstanding accuracy. Even the top pro DSLRs cannot beat it.
     
    Bruce, Jun 15, 2011
    #3
  4. RichA

    RichA Guest

    On Jun 15, 12:10 pm, bugbear <bugbear@trim_papermule.co.uk_trim>
    wrote:
    > Bruce wrote:
    >
    > > However, one thing that the new contrast-detect system offers is
    > > outstanding accuracy.  Even the top pro DSLRs cannot beat it.

    >
    > Surely it's unbeatable for accuracy, since it's literally
    > checking the focus at the sensor that will record
    > the final image. All other systems (AFAIK) need
    > to keep the focus system "in sync" with the final
    > image sensor, which must always carry some error,
    > no matter how small.
    >
    > I would welcome knowledge one way or the other.
    >
    >   BugBear


    The more plasticy the camera, the worse the phase focus accuracy
    because thermal expansion and contraction of the housings causes
    shifts in the focus distance from the lens to the sensor used for
    focusing. Mirrors and phase focusing will be gone soon.
     
    RichA, Jun 15, 2011
    #4
  5. RichA

    Bruce Guest

    bugbear <bugbear@trim_papermule.co.uk_trim> wrote:
    >Bruce wrote:
    >> However, one thing that the new contrast-detect system offers is
    >> outstanding accuracy. Even the top pro DSLRs cannot beat it.
    >>

    >
    >Surely it's unbeatable for accuracy, since it's literally
    >checking the focus at the sensor that will record
    >the final image. All other systems (AFAIK) need
    >to keep the focus system "in sync" with the final
    >image sensor, which must always carry some error,
    >no matter how small.
    >
    >I would welcome knowledge one way or the other.



    In theory, a contrast-detect AF system should always give pinpoint
    focus because, as you say, it is making its measurements on the sensor
    itself. But in practice, previous contrast-detect AF systems have
    been slow and hesitant, and the result is that they failed to focus on
    a moving subject.

    The new system is much faster, meaning that in most situations,
    results are much more decisive. But the system still falls short when
    the subject is moving quickly.

    Phase-detect systems tend to be quicker because they can sample more
    quickly. Therefore there is less scope for error. However, you are
    quite right to say that phase-detect systems include systematic
    errors, some more than others. Canon's system appears to cause more
    problems than Nikon's, but with careful calibration they will both
    produce similar results.

    So to sum up, contrast-detect systems have the potential for zero
    error but are still not as quick and decisive as phase detect systems,
    although the latest improvements close the gap or can even eliminate
    it for static and slow moving subjects. Phase-detect systems are fast
    and decisive but may include systematic errors that can only be
    eliminated by careful calibration of body and lens together.

    Personally, I'm still a fan of manual focus. ;-)
     
    Bruce, Jun 15, 2011
    #5
  6. On Jun 15, 11:10 am, bugbear <bugbear@trim_papermule.co.uk_trim>
    wrote:
    > Bruce wrote:
    >
    > > However, one thing that the new contrast-detect system offers is
    > > outstanding accuracy.  Even the top pro DSLRs cannot beat it.

    >
    > Surely it's unbeatable for accuracy, since it's literally
    > checking the focus at the sensor that will record
    > the final image. All other systems (AFAIK) need
    > to keep the focus system "in sync" with the final
    > image sensor, which must always carry some error,
    > no matter how small.
    >
    > I would welcome knowledge one way or the other.


    Matches my understanding -- and experiments.

    When focus is critical and time allows (which covers a few
    real photographic situations, and all lens-testing
    situations), I now try to use Live View in tripod mode on
    my D700, which uses contrast-based AF off the primary
    sensor, to set the focus.

    The very fast phase-detect AF in the D700 is wonderful for
    fast-moving subjects, even in quite low light, and I
    wouldn't give it up for anything I've seen from
    contrast-based AF yet (and "yet" is the important word
    there, I think). But absolutely, it's a more complex
    system, can get out of alignment, requires a mirror system
    and the corresponding thicker body, etc.
     
    David Dyer-Bennet, Jun 15, 2011
    #6
  7. RichA

    Bruce Guest

    John A. <> wrote:
    >On Wed, 15 Jun 2011 17:48:32 +0100, Bruce <>
    >wrote:
    >>bugbear <bugbear@trim_papermule.co.uk_trim> wrote:
    >>>Bruce wrote:
    >>>> However, one thing that the new contrast-detect system offers is
    >>>> outstanding accuracy. Even the top pro DSLRs cannot beat it.
    >>>>
    >>>
    >>>Surely it's unbeatable for accuracy, since it's literally
    >>>checking the focus at the sensor that will record
    >>>the final image. All other systems (AFAIK) need
    >>>to keep the focus system "in sync" with the final
    >>>image sensor, which must always carry some error,
    >>>no matter how small.
    >>>
    >>>I would welcome knowledge one way or the other.

    >>
    >>
    >>In theory, a contrast-detect AF system should always give pinpoint
    >>focus because, as you say, it is making its measurements on the sensor
    >>itself. But in practice, previous contrast-detect AF systems have
    >>been slow and hesitant, and the result is that they failed to focus on
    >>a moving subject.
    >>
    >>The new system is much faster, meaning that in most situations,
    >>results are much more decisive. But the system still falls short when
    >>the subject is moving quickly.
    >>
    >>Phase-detect systems tend to be quicker because they can sample more
    >>quickly. Therefore there is less scope for error. However, you are
    >>quite right to say that phase-detect systems include systematic
    >>errors, some more than others. Canon's system appears to cause more
    >>problems than Nikon's, but with careful calibration they will both
    >>produce similar results.
    >>
    >>So to sum up, contrast-detect systems have the potential for zero
    >>error but are still not as quick and decisive as phase detect systems,
    >>although the latest improvements close the gap or can even eliminate
    >>it for static and slow moving subjects. Phase-detect systems are fast
    >>and decisive but may include systematic errors that can only be
    >>eliminated by careful calibration of body and lens together.
    >>
    >>Personally, I'm still a fan of manual focus. ;-)

    >
    >And of course all systems are subject to the limits of how quickly and
    >precisely you can move the glass.



    Indeed. Going back a few years, that's why Canon's EOS lenses were so
    much faster to focus than "screwdriver drive" AF Nikkors, which led
    Nikon to pay for a very expensive license to use the USM technology.

    Nikon called it "Silent Wave Motor" rather than "Ultra Sonic Motor" as
    if it was their own technology, but it was Canon's. At some expense
    it transformed the focusing performance and the new AF-S Nikkors were
    every bit the equal of Canon USM lenses.

    Indeed, they were actually better, because Nikon did not share (at
    least, not to anything like the same extent) the systematic focusing
    errors that the EOS system suffered from.

    In recent years I think the patents may have expired because Nikon is
    putting silent wave motors in lenses across the range, including kit
    zooms. They would not be doing that if royalties had remained at the
    previous level.
     
    Bruce, Jun 15, 2011
    #7
  8. RichA

    Bruce Guest

    Doug Bashford <> wrote:
    >Re: Olympus about to surpass DSLR focus speed/accuracy?;
    > On Wed, 15 Jun 2011, Bruce wrote:
    >
    >> In recent years I think the patents may have expired because Nikon is
    >> putting silent wave motors in lenses across the range, including kit
    >> zooms. They would not be doing that if royalties had remained at the
    >> previous level.

    >
    >
    >As usual, when patents and copyrights expire,
    >the consumer and the economy wins!



    True, but without laws that protected intellectual property and
    allowed inventors and developers to profit from their work, a lot of
    technological development may never have happened.
     
    Bruce, Jul 1, 2011
    #8
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