Spots on dark pictures

Discussion in 'Digital Photography' started by Lars Bonnesen, Jan 1, 2005.

  1. When shooting dark area like the dark wall:

    http://fotos.eberhardt-bonnesen.dk/spots/spots.jpg

    I often get spots like indicated with the red arrows on the above pcture.

    Why do the come - are they reflections, dust on lens or some defect?

    Camera used is a Canon A95.

    Regards, Lars.
    Lars Bonnesen, Jan 1, 2005
    #1
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  2. Robert J Batina, Jan 1, 2005
    #2
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  3. "Robert J Batina" <> wrote in message
    news:GTCBd.46218$...
    >
    > http://www.imaging-resource.com/ARTS/HOT/HOT.HTM
    >
    > Vile things. (I'm guessing that is the problem... I can't get to the
    > image
    > right now... DNS issues.)


    I don't think that it is hotspots. I saw some examples of these, and it does
    not look like this.

    I now have corrected the DNS issue with the correct IP, so unless the wrong
    IP has been cached, it should work now. Can I ask you to take a look again?
    Sorry for the mistake.

    Regards, Lars.
    Lars Bonnesen, Jan 1, 2005
    #3
  4. Lars Bonnesen

    Dan Daniel Guest

    On Sat, 1 Jan 2005 19:40:20 +0100, "Lars Bonnesen" <none@noneæøå.com>
    wrote:

    >When shooting dark area like the dark wall:
    >
    >http://fotos.eberhardt-bonnesen.dk/spots/spots.jpg
    >
    >I often get spots like indicated with the red arrows on the above pcture.
    >
    >Why do the come - are they reflections, dust on lens or some defect?
    >
    >Camera used is a Canon A95.
    >
    >Regards, Lars.
    >


    Are the in the same location on the image no matter how you move the
    camera? They remind me of smudges on the CCD chip of a video camera
    which occurred when the chip was replaced, except mine were most
    visible on large light areas like gray sky (lots of noise in the dark
    area of old video cameras).
    Dan Daniel, Jan 1, 2005
    #4
  5. "Dan Daniel" <> wrote in message
    news:...

    > Are the in the same location on the image no matter how you move the
    > camera? They remind me of smudges on the CCD chip of a video camera
    > which occurred when the chip was replaced, except mine were most
    > visible on large light areas like gray sky (lots of noise in the dark
    > area of old video cameras).


    No, they are never at the same position.

    Regards, Lars.
    Lars Bonnesen, Jan 1, 2005
    #5
  6. Lars Bonnesen

    Jim Townsend Guest

    Lars Bonnesen wrote:

    > When shooting dark area like the dark wall:
    >
    > http://fotos.eberhardt-bonnesen.dk/spots/spots.jpg
    >
    > I often get spots like indicated with the red arrows on the above pcture.
    >
    > Why do the come - are they reflections, dust on lens or some defect?
    >
    > Camera used is a Canon A95.


    That's dust..

    The flash is *very* close to the lens. It illuminates any dust particles
    that are floating in the air in front of the lens.

    The particles show up as blobs because they are too close to be in focus.
    Jim Townsend, Jan 1, 2005
    #6
  7. "Jim Townsend" <> wrote in message
    news:...
    > Lars Bonnesen wrote:


    > That's dust..


    It is dust floating in the air? Then I understand why it doesn't help to
    clean the lens... (-;

    > The flash is *very* close to the lens. It illuminates any dust particles
    > that are floating in the air in front of the lens.


    The house is newly build, so there are dust "above average" in the house.

    But normally it should not be any problems having the flash that close (well
    I know of red-eye and so)?

    So if I get a couple of 300 W bulps, and places them a bit from the camera,
    the problem should go away?

    Regards, Lars.
    Lars Bonnesen, Jan 1, 2005
    #7
  8. Lars Bonnesen

    Ralph Mowery Guest

    > It is dust floating in the air? Then I understand why it doesn't help to
    > clean the lens... (-;
    >
    > > The flash is *very* close to the lens. It illuminates any dust

    particles
    > > that are floating in the air in front of the lens.

    >
    > The house is newly build, so there are dust "above average" in the house.
    >
    > But normally it should not be any problems having the flash that close

    (well
    > I know of red-eye and so)?
    >
    > So if I get a couple of 300 W bulps, and places them a bit from the

    camera,
    > the problem should go away?
    >
    > Regards, Lars.


    If it is dust (most likely is) then if you turn off the flash and use the
    room lights or other lights the problem should go away. The very bright
    reflections from the flash being right at the camera causes the reflections
    off the dust near the lense and you get the out of focus reflections from
    the dust particals.
    Ralph Mowery, Jan 1, 2005
    #8
  9. Lars Bonnesen

    Jim Townsend Guest

    Lars Bonnesen wrote:

    >
    > "Jim Townsend" <> wrote in message
    > news:...
    >> Lars Bonnesen wrote:

    >
    >> That's dust..

    >
    > It is dust floating in the air? Then I understand why it doesn't help to
    > clean the lens... (-;
    >
    >> The flash is *very* close to the lens. It illuminates any dust particles
    >> that are floating in the air in front of the lens.

    >
    > The house is newly build, so there are dust "above average" in the house.
    >
    > But normally it should not be any problems having the flash that close (well
    > I know of red-eye and so)?


    The problem with digital cameras is that the lenses have very small apertures.
    Even at f/2.8, the lens opening is tiny. This is because of the very small
    focal lengths needed to match the lens to the sensor.

    35mm compact film cameras have flashes close to the lens as well, but the
    larger apertures create a shallower depth of field. Dust in front of the
    lens is still illuminated, but is SO far out of focus it isn't a problem.

    The tiny digicam apertures have a very large depth of field and manage
    to get nearby dust specs in focus enough that they are a problem.


    > So if I get a couple of 300 W bulps, and places them a bit from the camera,
    > the problem should go away?


    It should. Just use them to illumiate the room. Your camera should be able
    to take room shots using ambient lightint and no flash. (As long as there
    isn't too much movement).. a couple of 300 Watt bulbs would definitely
    help.

    Just for fun. Set turn the flash on, focus on a dark background and
    shake a dusty blanket in the air right over the lens before you shoot.
    You'll see exactly what dust can do :)
    Jim Townsend, Jan 2, 2005
    #9
  10. Lars Bonnesen

    Ron Hunter Guest

    Lars Bonnesen wrote:
    > When shooting dark area like the dark wall:
    >
    > http://fotos.eberhardt-bonnesen.dk/spots/spots.jpg
    >
    > I often get spots like indicated with the red arrows on the above pcture.
    >
    > Why do the come - are they reflections, dust on lens or some defect?
    >
    > Camera used is a Canon A95.
    >
    > Regards, Lars.
    >
    >

    If you are using a flash, they could be reflections off dust motes in
    the air. I see them sometimes on flash shots in bad air. If they
    appear in the same place on multiple pictures, suspect dust on the lens,
    or (in the case of DSLRs), on the sensor.
    Ron Hunter, Jan 2, 2005
    #10
  11. Lars Bonnesen

    Ron Hunter Guest

    Lars Bonnesen wrote:
    > "Jim Townsend" <> wrote in message
    > news:...
    >
    >>Lars Bonnesen wrote:

    >
    >
    >>That's dust..

    >
    >
    > It is dust floating in the air? Then I understand why it doesn't help to
    > clean the lens... (-;
    >
    >
    >>The flash is *very* close to the lens. It illuminates any dust particles
    >>that are floating in the air in front of the lens.

    >
    >
    > The house is newly build, so there are dust "above average" in the house.
    >
    > But normally it should not be any problems having the flash that close (well
    > I know of red-eye and so)?
    >
    > So if I get a couple of 300 W bulps, and places them a bit from the camera,
    > the problem should go away?
    >
    > Regards, Lars.
    >
    >

    Yes, so would using a lower F-stop, if your camera has aperture priority
    settings. This would lower the depth of field, perhaps enough to make
    the dust problem imperceptible. If there is adequate ambient light, I
    always prefer to shoot without flash.
    Ron Hunter, Jan 2, 2005
    #11
  12. Lars Bonnesen

    Ron Hunter Guest

    Jim Townsend wrote:
    > Lars Bonnesen wrote:
    >
    >
    >>"Jim Townsend" <> wrote in message
    >>news:...
    >>
    >>>Lars Bonnesen wrote:

    >>
    >>>That's dust..

    >>
    >>It is dust floating in the air? Then I understand why it doesn't help to
    >>clean the lens... (-;
    >>
    >>
    >>>The flash is *very* close to the lens. It illuminates any dust particles
    >>>that are floating in the air in front of the lens.

    >>
    >>The house is newly build, so there are dust "above average" in the house.
    >>
    >>But normally it should not be any problems having the flash that close (well
    >>I know of red-eye and so)?

    >
    >
    > The problem with digital cameras is that the lenses have very small apertures.
    > Even at f/2.8, the lens opening is tiny. This is because of the very small
    > focal lengths needed to match the lens to the sensor.
    >
    > 35mm compact film cameras have flashes close to the lens as well, but the
    > larger apertures create a shallower depth of field. Dust in front of the
    > lens is still illuminated, but is SO far out of focus it isn't a problem.
    >
    > The tiny digicam apertures have a very large depth of field and manage
    > to get nearby dust specs in focus enough that they are a problem.
    >
    >
    >
    >>So if I get a couple of 300 W bulps, and places them a bit from the camera,
    >>the problem should go away?

    >
    >
    > It should. Just use them to illumiate the room. Your camera should be able
    > to take room shots using ambient lightint and no flash. (As long as there
    > isn't too much movement).. a couple of 300 Watt bulbs would definitely
    > help.
    >
    > Just for fun. Set turn the flash on, focus on a dark background and
    > shake a dusty blanket in the air right over the lens before you shoot.
    > You'll see exactly what dust can do :)
    >
    >
    >

    Or, take a flash picture of a light snow falling.
    Amazing the effect you get.
    Ron Hunter, Jan 2, 2005
    #12
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