Occasional poor auto-focus on Minolta A1

Discussion in 'Digital Photography' started by Martin Underwood, Jul 14, 2004.

  1. Has anyone else found that their Minolta A1 occasionally gives a "correct
    focus" indication (green dot in viewfinder) but the resulting photo is out
    of focus?

    I've eliminated camera-shake as the cause of my blurred photos (some blurred
    ones are at 1/1000 sec). It seems to be mainly when the lens is towards the
    wide-angle end of the zoom and it's when I'm taking pictures where the whole
    of the subject is at infinity - there's no window or nearby piece of grass
    that the camera could be focussing on, yet the result is as if it had
    focussed at about 1 metre. Sadly the viewfinder and back-of-camera screen
    are not good enough to use as focussing aids, and the picture appears sharp
    when viewed at normal size: you can only tell that it's blurred when you
    zoom right in.

    Before I return the camera as faulty, I wanted to gauge how widespread the
    problem is.
     
    Martin Underwood, Jul 14, 2004
    #1
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  2. Martin Underwood

    Ed Ruf Guest

    On Wed, 14 Jul 2004 15:30:03 +0100, in rec.photo.digital "Martin
    Underwood" <> wrote:

    >Has anyone else found that their Minolta A1 occasionally gives a "correct
    >focus" indication (green dot in viewfinder) but the resulting photo is out
    >of focus?
    >
    >I've eliminated camera-shake as the cause of my blurred photos (some blurred
    >ones are at 1/1000 sec). It seems to be mainly when the lens is towards the
    >wide-angle end of the zoom and it's when I'm taking pictures where the whole
    >of the subject is at infinity - there's no window or nearby piece of grass
    >that the camera could be focussing on, yet the result is as if it had
    >focussed at about 1 metre. Sadly the viewfinder and back-of-camera screen
    >are not good enough to use as focussing aids, and the picture appears sharp
    >when viewed at normal size: you can only tell that it's blurred when you
    >zoom right in.
    >
    >Before I return the camera as faulty, I wanted to gauge how widespread the
    >problem is.


    First, does the exif info contain any focus distance info to verify
    your contention?
    ________________________________________________________
    Ed Ruf Lifetime AMA# 344007 ()
    See images taken with my CP-990 and 5700 at
    http://EdwardGRuf.com
     
    Ed Ruf, Jul 14, 2004
    #2
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  3. Martin Underwood

    Clyde Guest

    Martin Underwood wrote:

    > Has anyone else found that their Minolta A1 occasionally gives a "correct
    > focus" indication (green dot in viewfinder) but the resulting photo is out
    > of focus?
    >
    > I've eliminated camera-shake as the cause of my blurred photos (some blurred
    > ones are at 1/1000 sec). It seems to be mainly when the lens is towards the
    > wide-angle end of the zoom and it's when I'm taking pictures where the whole
    > of the subject is at infinity - there's no window or nearby piece of grass
    > that the camera could be focussing on, yet the result is as if it had
    > focussed at about 1 metre. Sadly the viewfinder and back-of-camera screen
    > are not good enough to use as focussing aids, and the picture appears sharp
    > when viewed at normal size: you can only tell that it's blurred when you
    > zoom right in.
    >
    > Before I return the camera as faulty, I wanted to gauge how widespread the
    > problem is.
    >
    >


    My 7Hi does that. I use only the point focusing and never the wide, but
    every now and then I just get an out of focus image. I always check to
    make sure the dot is white too.

    I don't know why this happens, but it does make me shoot 2 or 3 of
    everything.

    Clyde
     
    Clyde, Jul 14, 2004
    #3
  4. "Clyde" <> wrote in message
    news:GecJc.78915$IQ4.30779@attbi_s02...
    > Martin Underwood wrote:
    >
    > > Has anyone else found that their Minolta A1 occasionally gives a

    "correct
    > > focus" indication (green dot in viewfinder) but the resulting photo is

    out
    > > of focus?
    > >
    > > I've eliminated camera-shake as the cause of my blurred photos (some

    blurred
    > > ones are at 1/1000 sec). It seems to be mainly when the lens is towards

    the
    > > wide-angle end of the zoom and it's when I'm taking pictures where the

    whole
    > > of the subject is at infinity - there's no window or nearby piece of

    grass
    > > that the camera could be focussing on, yet the result is as if it had
    > > focussed at about 1 metre. Sadly the viewfinder and back-of-camera

    screen
    > > are not good enough to use as focussing aids, and the picture appears

    sharp
    > > when viewed at normal size: you can only tell that it's blurred when you
    > > zoom right in.
    > >
    > > Before I return the camera as faulty, I wanted to gauge how widespread

    the
    > > problem is.

    >
    > My 7Hi does that. I use only the point focusing and never the wide, but
    > every now and then I just get an out of focus image. I always check to
    > make sure the dot is white too.
    >
    > I don't know why this happens, but it does make me shoot 2 or 3 of
    > everything.


    Ah, it happens with the 7Hi as well, does it? My dad's got a 7i and has
    never had a problem.

    I always use cross-hair (point) focussing and not rectangle (region)
    focussing - except when it changes back spontaneously and I don't notice!
    But I'm confident that I've had focussing problems with both focussing modes
    and I know that it's happened when I've had a focus confirmation rather than
    a red "cannot focus" signal.

    Unfortunately the focus distance is one of the few parameters which isn't
    recorded in the EXIF information - that was the first place I looked to see
    what the camera had focussed on. I'm guessing that it's focussing too close
    based on the fact that everything is blurred, but that closer objects look
    slightly sharper than distant objects. Unfortunately it's so rare that I
    can't do any tests to see if the focus is better at a smaller aperture than
    a large one due to depth of field.

    Could a polarising filter affect focussing? I'm not sure whether mine is a
    linear or a circular filter, but I'd have thought that if it was affecting
    focussing, it would be an all-or-nothing thing: that I'd get "failed to
    focus" rather focussing very close instead of at infinity.

    I know what you mean about needing to take several pictures. The only time
    it occurs is when I don't bother to check before leaving the scene I was
    photographing :-( I tend to take three bracketed photos anyway to choose
    the best exposure.
     
    Martin Underwood, Jul 14, 2004
    #4
  5. Martin Underwood

    Clyde Guest

    Martin Underwood wrote:

    > "Clyde" <> wrote in message
    > news:GecJc.78915$IQ4.30779@attbi_s02...
    >
    >>Martin Underwood wrote:
    >>
    >>
    >>>Has anyone else found that their Minolta A1 occasionally gives a

    >
    > "correct
    >
    >>>focus" indication (green dot in viewfinder) but the resulting photo is

    >
    > out
    >
    >>>of focus?
    >>>
    >>>I've eliminated camera-shake as the cause of my blurred photos (some

    >
    > blurred
    >
    >>>ones are at 1/1000 sec). It seems to be mainly when the lens is towards

    >
    > the
    >
    >>>wide-angle end of the zoom and it's when I'm taking pictures where the

    >
    > whole
    >
    >>>of the subject is at infinity - there's no window or nearby piece of

    >
    > grass
    >
    >>>that the camera could be focussing on, yet the result is as if it had
    >>>focussed at about 1 metre. Sadly the viewfinder and back-of-camera

    >
    > screen
    >
    >>>are not good enough to use as focussing aids, and the picture appears

    >
    > sharp
    >
    >>>when viewed at normal size: you can only tell that it's blurred when you
    >>>zoom right in.
    >>>
    >>>Before I return the camera as faulty, I wanted to gauge how widespread

    >
    > the
    >
    >>>problem is.

    >>
    >>My 7Hi does that. I use only the point focusing and never the wide, but
    >>every now and then I just get an out of focus image. I always check to
    >>make sure the dot is white too.
    >>
    >>I don't know why this happens, but it does make me shoot 2 or 3 of
    >>everything.

    >
    >
    > Ah, it happens with the 7Hi as well, does it? My dad's got a 7i and has
    > never had a problem.
    >
    > I always use cross-hair (point) focussing and not rectangle (region)
    > focussing - except when it changes back spontaneously and I don't notice!
    > But I'm confident that I've had focussing problems with both focussing modes
    > and I know that it's happened when I've had a focus confirmation rather than
    > a red "cannot focus" signal.
    >
    > Unfortunately the focus distance is one of the few parameters which isn't
    > recorded in the EXIF information - that was the first place I looked to see
    > what the camera had focussed on. I'm guessing that it's focussing too close
    > based on the fact that everything is blurred, but that closer objects look
    > slightly sharper than distant objects. Unfortunately it's so rare that I
    > can't do any tests to see if the focus is better at a smaller aperture than
    > a large one due to depth of field.
    >
    > Could a polarising filter affect focussing? I'm not sure whether mine is a
    > linear or a circular filter, but I'd have thought that if it was affecting
    > focussing, it would be an all-or-nothing thing: that I'd get "failed to
    > focus" rather focussing very close instead of at infinity.
    >
    > I know what you mean about needing to take several pictures. The only time
    > it occurs is when I don't bother to check before leaving the scene I was
    > photographing :-( I tend to take three bracketed photos anyway to choose
    > the best exposure.
    >
    >

    I don't use a polarizing filter at all. So, I doubt that's it. I don't
    know what it doing it though.

    Clyde
     
    Clyde, Jul 15, 2004
    #5
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