Depth of Field

Discussion in 'Digital Photography' started by yvon4jon@aol.com, Sep 9, 2006.

  1. Guest

    I recently purchased a Cannon PowerShot A520 digital camera. I've
    gotten pretty good with using many of the features, but I'm still
    having a hard time in getting the right "depth" of field shots to look
    like the background is blurred and the focus is on the object/person in
    front.

    Do I have to get a pricey SLR to achieve this effect.

    Please advise....

    Thanks,

    Vonni
    , Sep 9, 2006
    #1
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  2. Roy G Guest

    <> wrote in message
    news:...
    >I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.
    >
    > Please advise....
    >
    > Thanks,
    >
    > Vonni
    >


    Hi.

    You will need to experiment with the camera. The small sensor cameras have
    a large Depth of Field.

    The Maximum Aperture setting will reduce the Depth, the longest Focal Length
    will also reduce it, and the closer the subject is to the Camera will also
    reduce it.

    The larger the sensor, the smaller the DoF. so APS size or Full Frame might
    be the way to go.

    Before anyone nit-picks, it is not actually the sensor which determines DoF
    it is the focal length of the lenses, but those are normally tied in with
    Sensor sizes.

    Roy G
    Roy G, Sep 9, 2006
    #2
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  3. Jim Guest

    <> wrote in message
    news:...
    >I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.
    >
    > Please advise....
    >
    > Thanks,
    >
    > Vonni
    >

    If your camera does not allow you to set the aperature, you will never be
    able to control depth of field. You want a camera that has aperature
    priority exposure control and which can display the view at the taking
    aperature on the LCD screen. There aren't many cameras like that anymore.

    Another way would be to use the above described camera and consult depth of
    field tables. You need to be careful about where you get such tables for
    most of them will be computed with a circle of confusion that is appropriate
    for 35mm film images. The circle of confusion for digital cameras is almost
    certain to be different.

    By the way, it isn't especially easy to do this on a "pricey SLR" either
    because stopping down to the taking aperature has disappeared in recent
    years.
    Jim
    Jim, Sep 9, 2006
    #3
  4. wrote:
    > I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.

    An SLR makes it easier, but it can be achieved on a P&S to some extent.
    If your camera has an "A" setting, use it, and dial in the smallest
    number (which means largest aperture) that you can select. If your
    camera doesn't have the "A" setting, select a portrait program mode.
    Also, it helps to zoom in a bit.
    Doing this will make your camera use the least DOF that it is possible
    to achieve. If this still doesn't give you much out-of-focus effect,
    then you will have to upgrade to a camera with a larger sensor (and
    correspondingly longer focal length lens for any particular angle of
    view) and/or a lens that has a faster maximum aperture (ie, smaller
    number for aperture)
    >
    > Please advise....
    >
    > Thanks,
    >
    > Vonni
    >
    Graham Fountain, Sep 9, 2006
    #4
  5. <> wrote in message
    news:...
    >I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.


    You could get a Canon 350D (look for one on sale before or just after the
    400D comes out) and the 50/1.8 (about US$ 70 or so for the lens). Not all
    that pricey.

    The A520 lens is f/5.5 at the long end, so it's hard. It would be a bit
    easier with the A700, even more so with the S3.

    Set the camera to "A" (or "Av") mode, select the widest aperture (f/5.5),
    and (this is important) zoom out to the longest focal length. Another
    important thing is to get as close as possible to your subject. If it's a
    portrait, make it a tightly cropped head shot.

    The wide aperture, long focal length, and close focusing distance all work
    to blur the background.

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Sep 10, 2006
    #5
  6. Paul Rubin Guest

    writes:
    > I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.


    You can do a pretty good imitation using an image editor.

    http://www.gimpguru.org/Tutorials/SimulatedDOF/
    Paul Rubin, Sep 10, 2006
    #6
  7. ASAAR Guest

    On Sun, 10 Sep 2006 08:51:53 +0900, David J. Littleboy wrote:

    > Set the camera to "A" (or "Av") mode, select the widest aperture (f/5.5),
    > and (this is important) zoom out to the longest focal length. Another
    > important thing is to get as close as possible to your subject. If it's a
    > portrait, make it a tightly cropped head shot.
    >
    > The wide aperture, long focal length, and close focusing distance all work
    > to blur the background.


    Last night I had the strangest dream . . . In it, a lab
    technician (no bubbling beakers) tested myriad cameras and lenses,
    furiously taking notes and double checking all entries. Then he
    pondered the effect of constraining the exposure settings to some
    function of uniform photon capture, shouted "Eureka!" and promptly
    set about writing a paper titled "The Long Focal Length Myth".
    ASAAR, Sep 10, 2006
    #7
  8. jeremy Guest

    <> wrote in message
    news:...
    >I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.
    >
    > Please advise....
    >
    > Thanks,
    >
    > Vonni
    >


    Some digital cameras feature "portrait" mode, which is usually optimized for
    shallow depth of field. If your camera allows you to set the aperture,
    select the widest and shoot. You can obtain even shallower DOF by shooting
    at telephoto focal lengths, but that may not suit the kind of shot you want
    to take.

    Ironically, you don't need a "pricey SLR," just one with lenses that can be
    manually set. The old Pentax K-1000, as basic as they get, allows this with
    ease. Of course you would want to couple the camera with a fast lens, like
    the 50// f/1.4 or 50mm f/1.7, and then shoot at wide open or near wide open.

    Just one word of caution: shooting wide open typically results in images
    that are significantly softer. I had always known this, but only from
    seeing the test reports. That point was made to hit home much more when I
    saw actual comparison photos of shots taken with the same lens but at
    different aperture settings, on Ken Rockwell's web site. He actually
    concluded that one's aperture setting made more of a difference in image
    sharpness than one's choice of lens brand. So be careful to properly focus
    your shot when shooting wide open. You can have a look at the comparison
    shots at this link:

    http://www.kenrockwell.com/nikon/50-comparison/f-stops.htm
    jeremy, Sep 10, 2006
    #8
  9. tomm42 Guest


    >
    > Last night I had the strangest dream . . . In it, a lab
    > technician (no bubbling beakers) tested myriad cameras and lenses,
    > furiously taking notes and double checking all entries. Then he
    > pondered the effect of constraining the exposure settings to some
    > function of uniform photon capture, shouted "Eureka!" and promptly
    > set about writing a paper titled "The Long Focal Length Myth".


    Man, you have some weird dreams, about on par with a lab tech that once
    told me she dreamed about be raped by an enlarger. Anyway......
    What do you mean by "The Long Focal Length Myth"(all focal lengths in
    35mm terms). It is standard practice to do head shots and anything down
    to a person's waist with a 80mm or longer. Of course above 200mm you
    start to flatten everything out. You can use a 35mm for full length
    portrait or groups but anything wider will get you distortion, easy
    tests to do. Even a 50mm will give some distortion to head shots. This
    is just common knowlege of lens characteristics. Again it is easily
    testable.

    Tom
    tomm42, Sep 10, 2006
    #9
  10. tomm42 wrote:

    >> Last night I had the strangest dream . . . In it, a lab
    >>technician (no bubbling beakers) tested myriad cameras and lenses,
    >>furiously taking notes and double checking all entries. Then he
    >>pondered the effect of constraining the exposure settings to some
    >>function of uniform photon capture, shouted "Eureka!" and promptly
    >>set about writing a paper titled "The Long Focal Length Myth".

    >
    >
    > Man, you have some weird dreams, about on par with a lab tech that once
    > told me she dreamed about be raped by an enlarger. Anyway......
    > What do you mean by "The Long Focal Length Myth"(all focal lengths in
    > 35mm terms). It is standard practice to do head shots and anything down
    > to a person's waist with a 80mm or longer. Of course above 200mm you
    > start to flatten everything out. You can use a 35mm for full length
    > portrait or groups but anything wider will get you distortion, easy
    > tests to do. Even a 50mm will give some distortion to head shots. This
    > is just common knowlege of lens characteristics. Again it is easily
    > testable.
    >
    > Tom


    It wasn't a dream. It was from a thread a while back.

    The Depth-of-Field Myth and Digital Cameras
    http://www.clarkvision.com/photoinfo/dof_myth

    But start here first, then read the above article.

    Digital Cameras: Does Pixel Size Matter?
    Factors in Choosing a Digital Camera
    http://www.clarkvision.com/imagedetail/does.pixel.size.matter

    Roger
    Roger N. Clark (change username to rnclark), Sep 10, 2006
    #10
  11. wrote:
    > I recently purchased a Cannon PowerShot A520 digital camera. I've
    > gotten pretty good with using many of the features, but I'm still
    > having a hard time in getting the right "depth" of field shots to look
    > like the background is blurred and the focus is on the object/person in
    > front.
    >
    > Do I have to get a pricey SLR to achieve this effect.
    >
    > Please advise....
    >
    > Thanks,
    >
    > Vonni


    An SLR sure helps- a true SLR with optical viewfinder.

    The problem is that you must manually focus, and focus selectively on
    just the plane that you want to be in good focus. That requires the
    ability to SEE proper focus. You cannot focus a 5 or 6 MP camera by
    judging the focus on a 200KP LCD screen.
    Don Stauffer in Minnesota, Sep 10, 2006
    #11
  12. ASAAR Guest

    On 10 Sep 2006 05:23:11 -0700, tomm42 wrote:

    >> Last night I had the strangest dream . . . In it, a lab
    >> technician (no bubbling beakers) tested myriad cameras and lenses,
    >> furiously taking notes and double checking all entries. Then he
    >> pondered the effect of constraining the exposure settings to some
    >> function of uniform photon capture, shouted "Eureka!" and promptly
    >> set about writing a paper titled "The Long Focal Length Myth".

    >
    > Man, you have some weird dreams, about on par with a lab tech that once
    > told me she dreamed about be raped by an enlarger. Anyway......
    > What do you mean by "The Long Focal Length Myth"(all focal lengths in
    > 35mm terms). It is standard practice to do head shots and anything down
    > to a person's waist with a 80mm or longer. Of course above 200mm you
    > start to flatten everything out. You can use a 35mm for full length
    > portrait or groups but anything wider will get you distortion, easy
    > tests to do. Even a 50mm will give some distortion to head shots. This
    > is just common knowlege of lens characteristics. Again it is easily
    > testable.


    Just an attempt at some newsgroup satire, in that there are a
    couple of newsgroup denizens who don't appear to be satisfied with
    the advantages that their Canons (with their "superzize me" sensors)
    give them. This has resulted in several technical papers (see URL
    below for one) that delve into the intricacies of sensors, pixels,
    full wells and noise, and purport to contain mythbusters, such as
    "The f/ratio Myth" which, as described in numerous newsgroup
    messages here, attempts to show that P&S cameras, with their small
    sensors, don't really provide greater Depths Of Field than DSLRs.
    That the supposed f/ratio Myth is never really defined doesn't seem
    to matter very much, and this is easy to overlook, what with the
    arcane proof, provided with much hand waving and technical mumbo
    jumbo, complete with 24 8X10 color, glossy photos with circles and
    arrows on the front and a paragraph on the back of each one
    explaining uh, something or other. This isn't to say that the
    papers don't provide some useful or interesting information along
    the way. But their murky details are useful for facilitating the
    use of tortured, convoluted logic in the service of myth-busting.

    URL: http://www.clarkvision.com/imagedetail/does.pixel.size.matter
    ASAAR, Sep 10, 2006
    #12
  13. ASAAR wrote:
    > On 10 Sep 2006 05:23:11 -0700, tomm42 wrote:
    >
    >
    >>> Last night I had the strangest dream . . . In it, a lab
    >>>technician (no bubbling beakers) tested myriad cameras and lenses,
    >>>furiously taking notes and double checking all entries. Then he
    >>>pondered the effect of constraining the exposure settings to some
    >>>function of uniform photon capture, shouted "Eureka!" and promptly
    >>>set about writing a paper titled "The Long Focal Length Myth".

    >>
    >>Man, you have some weird dreams, about on par with a lab tech that once
    >>told me she dreamed about be raped by an enlarger. Anyway......
    >>What do you mean by "The Long Focal Length Myth"(all focal lengths in
    >>35mm terms). It is standard practice to do head shots and anything down
    >>to a person's waist with a 80mm or longer. Of course above 200mm you
    >>start to flatten everything out. You can use a 35mm for full length
    >>portrait or groups but anything wider will get you distortion, easy
    >>tests to do. Even a 50mm will give some distortion to head shots. This
    >>is just common knowlege of lens characteristics. Again it is easily
    >>testable.

    >
    >
    > Just an attempt at some newsgroup satire, in that there are a
    > couple of newsgroup denizens who don't appear to be satisfied with
    > the advantages that their Canons (with their "superzize me" sensors)
    > give them.


    It has nothing to do with Canons or any other brand.
    It is simple physics.

    > This has resulted in several technical papers (see URL
    > below for one) that delve into the intricacies of sensors, pixels,
    > full wells and noise, and purport to contain mythbusters, such as
    > "The f/ratio Myth" which, as described in numerous newsgroup
    > messages here, attempts to show that P&S cameras, with their small
    > sensors, don't really provide greater Depths Of Field than DSLRs.


    It's actually pixel size, not whether the pixels are in a P&S camera
    or a DSLR.

    > That the supposed f/ratio Myth is never really defined doesn't seem
    > to matter very much, and this is easy to overlook, what with the
    > arcane proof, provided with much hand waving and technical mumbo
    > jumbo, complete with 24 8X10 color, glossy photos with circles and
    > arrows on the front and a paragraph on the back of each one
    > explaining uh, something or other.


    Don't like the answer? Attack the messenger.

    > This isn't to say that the
    > papers don't provide some useful or interesting information along
    > the way. But their murky details are useful for facilitating the
    > use of tortured, convoluted logic in the service of myth-busting.
    >
    > URL: http://www.clarkvision.com/imagedetail/does.pixel.size.matter


    If you can find a flaw in the arguments, let me know.
    If you have a specific question, I'll try and answer it.
    But simply criticizing the work as mumbo jumbo
    and murky details does nothing to help anyone,
    and doesn't help your case.

    Here is another argument:
    http://www.stanmooreastro.com/f_ratio_myth.htm

    Roger
    Roger N. Clark (change username to rnclark), Sep 11, 2006
    #13
  14. ASAAR Guest

    On Sun, 10 Sep 2006 18:54:12 -0700, Roger N. Clark (change username
    to rnclark) wrote:

    >> Just an attempt at some newsgroup satire, in that there are a
    >> couple of newsgroup denizens who don't appear to be satisfied with
    >> the advantages that their Canons (with their "superzize me" sensors)
    >> give them.

    >
    > It has nothing to do with Canons or any other brand.
    > It is simple physics.


    You seem to be exceptionally sensitive, to the point that you're
    seeing yourself as a target or victim when it was others I had in
    mind. Another of the participants in the thread strenuously arguing
    the DOF myth was Littleboy, who is a self-admitted Canon snob or
    bigot, and who almost regularly denounces Nikons, with their
    "insanely small pixels". I don't see you showing that kind of brand
    bias, but you (and you're not the only one) do seem to avoid making
    your points as clearly and simply as possible, often making a few
    complex statements and then saying essentially "read my paper at..."


    >> That the supposed f/ratio Myth is never really defined doesn't seem
    >> to matter very much, and this is easy to overlook, what with the
    >> arcane proof, provided with much hand waving and technical mumbo
    >> jumbo, complete with 24 8X10 color, glossy photos with circles and
    >> arrows on the front and a paragraph on the back of each one
    >> explaining uh, something or other.

    >
    > Don't like the answer? Attack the messenger.


    Don't be absurd. There's no attack here and you evidently have
    either lived in a cocoon or are too young to have failed to
    recognized the humorous reference to A. Guthrie. And if you're the
    messenger (who was NOT attacked), who, precisely, created the
    message? Do try to reign in your sensitivity, or some may mistake
    it for paranoia. And if you think this is an attack, you just don't
    get it.


    > If you can find a flaw in the arguments, let me know.
    > If you have a specific question, I'll try and answer it.


    I've told you (after proofing your paper) that there was a problem
    with "The f/ratio Myth" not clearly stating what the myth actually
    was, so whatever your handwaving accomplished, it disproved nothing.
    You chose to curtly acknowledge the proofreading but ignored my
    request for a clear description of the myth.


    > Here is another argument:
    > http://www.stanmooreastro.com/f_ratio_myth.htm


    What he says is somewhat similar to what you've said, but if
    carefully read, *he* makes clear that he really hasn't disproved any
    f_ratio myth at all. He's just saying that at exposure extremes
    (such as his use of 10 minute shutter speeds), other factors begin
    to play a significant role. I really couldn't care less about your
    photon noise arguments. I've been consistently talking about depth
    of field, and if it takes a dim shot in a coal mine to prove that a
    DSLR can have as great a DOF as a P&S with a small sensor, that may
    satisfy you and Littleboy. But most people take pictures under
    conditions where their camera's sensors aren't photon starved. If
    that was the rule, there wouldn't be much point in cameras providing
    histograms.
    ASAAR, Sep 11, 2006
    #14
  15. Paul Rubin Guest

    ASAAR <> writes:
    > I've told you (after proofing your paper) that there was a problem
    > with "The f/ratio Myth" not clearly stating what the myth actually
    > was, so whatever your handwaving accomplished, it disproved nothing.
    > You chose to curtly acknowledge the proofreading but ignored my
    > request for a clear description of the myth.


    I did not see any unclarity. The myth is that if you take some
    picture with a DSLR and then take the same picture with a small-sensor
    P/S, the P/S picture will have more DOF because of P/S's shorter lens.
    E.g., imagine you're shooting at the same exposure time and f/ratio,
    say 1/125th at f/8, with the zoom set to 50mm on the DSLR and 10mm on
    the P/S. A 10mm lens will have more DOF at f/8 than a 50mm lens will
    have at f/8.

    The "disproof" is basically that the DSLR gives comparable quality at
    higher ISO, so you can stop the lens down more and get the DOF back.

    The dis-disproof is that in practice you may simply accept noisier
    images from the P/S, so you -do- get that additional DOF.

    Here's a good old article about similar considerations from the film era:

    http://www.minoxlab.com/PZ051897/peterd.htm
    Paul Rubin, Sep 11, 2006
    #15
  16. ASAAR wrote:

    > I've been consistently talking about depth
    > of field, and if it takes a dim shot in a coal mine to prove that a
    > DSLR can have as great a DOF as a P&S with a small sensor, that may
    > satisfy you and Littleboy. But most people take pictures under
    > conditions where their camera's sensors aren't photon starved. If
    > that was the rule, there wouldn't be much point in cameras providing
    > histograms.


    The argument regarding depth of field and f/ratio myths has
    nothing to do with being photon starved. All decent digital
    cameras, from the best DSLRs to small sensor point and
    shoots take images in normal conditions that are dominated
    by photon noise (Poisson statistics). It is that property
    that leads to the conclusions in my articles, whether in
    bright sunlight at ISO 100 and 1/1000 second exposures,
    or dim room light at iso 400 and seconds long exposures.
    It has nothing to do with histograms.

    Roger
    Roger N. Clark (change username to rnclark), Sep 11, 2006
    #16
  17. ASAAR Guest

    On 10 Sep 2006 21:05:41 -0700, Paul Rubin
    <http://> wrote:

    >> I've told you (after proofing your paper) that there was a problem
    >> with "The f/ratio Myth" not clearly stating what the myth actually
    >> was, so whatever your handwaving accomplished, it disproved nothing.
    >> You chose to curtly acknowledge the proofreading but ignored my
    >> request for a clear description of the myth.

    >
    > I did not see any unclarity. The myth is that if you take some
    > picture with a DSLR and then take the same picture with a small-sensor
    > P/S, the P/S picture will have more DOF because of P/S's shorter lens.
    > E.g., imagine you're shooting at the same exposure time and f/ratio,
    > say 1/125th at f/8, with the zoom set to 50mm on the DSLR and 10mm on
    > the P/S. A 10mm lens will have more DOF at f/8 than a 50mm lens will
    > have at f/8.


    That may be because you haven't seen most of the messages in the
    thread arguing this point. Examples were given with a P&S camera
    that had only a slightly smaller sensor than an APS-C DSLR. Several
    people showed that with the much smaller sensors found in the
    majority of P&S cameras, the DSLR would have to use an impractically
    small aperture to match the DOF (such as smaller than f/32 or f/45).
    It's one thing to say that if really pushed, a DSLR can take
    pictures with a very large DOF, understanding that due to
    diffraction and other effects the picture quality will suffer
    greatly, resulting in a big, expensive DSLR that takes no better
    pictures than a cheap P&S. It's another thing to hide that
    diminished quality, and boldly proclaim DLSRs have the same DOF
    capability as smaller P&S cameras.

    This was the point made by Littleboy, who conveniently left out
    the fact that he'd probably be the last person around who would
    tolerate low quality shots from his cameras. If fact he practically
    admitted that a couple of days ago when he stated that he was high
    quality photo snob. (see quote below) It doesn't make for a sound
    argument to say that a DSLR has a capability when its quality is
    such that you'd never want to take advantage of it.

    >> David J. Littleboy wrote:
    >>>
    >>>I was comparing P&S with serious (some might say pretentious) photography;
    >>>they're different beasts with different properties, regardless of whether
    >>>you are shooting film or digital.

    >>
    >> I understand what you mean by them being different, and obviously
    >> different tools are needed for different situations.
    >>
    >> But geezes, you're not one of those snobs, are you?

    >
    > Very much so. There's something incredibly beautiful about high-quality
    > photographs (real photographs, you know, the ones on paper in galleries).
    ASAAR, Sep 11, 2006
    #17
  18. ASAAR Guest

    On Sun, 10 Sep 2006 21:19:42 -0700, Roger N. Clark (change username
    to rnclark) wrote:

    >> I've been consistently talking about depth
    >> of field, and if it takes a dim shot in a coal mine to prove that a
    >> DSLR can have as great a DOF as a P&S with a small sensor, that may
    >> satisfy you and Littleboy. But most people take pictures under
    >> conditions where their camera's sensors aren't photon starved. If
    >> that was the rule, there wouldn't be much point in cameras providing
    >> histograms.

    >
    > The argument regarding depth of field and f/ratio myths has
    > nothing to do with being photon starved. All decent digital
    > cameras, from the best DSLRs to small sensor point and
    > shoots take images in normal conditions that are dominated
    > by photon noise (Poisson statistics). It is that property
    > that leads to the conclusions in my articles, whether in
    > bright sunlight at ISO 100 and 1/1000 second exposures,
    > or dim room light at iso 400 and seconds long exposures.
    > It has nothing to do with histograms.


    Dominated by photon noise? I strongly disagree, unless we're
    using totally different definitions of words allowing us to talk
    past each other without realizing it. Let me give an analogy using
    AM radios. Tune to a clear spot of the band between stations and
    turn up the volume slightly. You'll hear *noise*. That noise also
    exists on station frequencies, but you normally don't hear the noise
    because the station's signal is so much greater than the noise
    signal. But tune in to a weak station (typically found at night)
    and the noise will be clearly heard. So much so at times that the
    station's signal is unintelligible. In such conditions I'd say that
    the background noise dominates, making it difficult to hear the
    station. But this is not a typical situation for most people. They
    tend to listen to stations having much stronger signals, and so they
    wouldn't hear the background "noise". Using your word definitions
    it seems as if you'd say that even when tuned to a strong station
    under normal conditions, the sound would somehow still be dominated
    by noise. That is NOT what people experience. The only way I could
    understand you saying that is if you'd also consider the station's
    signal to be a form of noise. But if that's the case then we'll
    never get very far arguing points, since your definitions would be
    contrary to common understanding, and it would be incumbent upon you
    to declare your unusual definitions in advance, since presumably
    *you* would be aware of both definitions, but we mere mortals would
    only be aware of the non-technoid definitions.
    ASAAR, Sep 11, 2006
    #18
  19. DHB Guest

    On 9 Sep 2006 13:28:22 -0700, wrote:

    >I recently purchased a Cannon PowerShot A520 digital camera. I've
    >gotten pretty good with using many of the features, but I'm still
    >having a hard time in getting the right "depth" of field shots to look
    >like the background is blurred and the focus is on the object/person in
    >front.
    >
    >Do I have to get a pricey SLR to achieve this effect.
    >
    >Please advise....
    >
    >Thanks,
    >
    >Vonni

    Vonni,
    You already got some very good answers so I won't try to
    reinvent the wheel.

    Here is a useful on-line DOF calculator I have used to set
    some of my P&S camera's "C" Custom mode as a pre-focused mode:

    http://www.dofmaster.com/dofjs.html

    For me I generally use it to help me calculate the range of
    acceptable focus @ a given focal length, f-stop when pre-focused to
    "X" distance. This let's me take candid pictures quickly & without
    waiting for the camera to attain *focus lock* & without worry that it
    might focus on some object behind or in front of he/she/them. All I
    need to do then is make sure the subject is within the calculated
    distance range.

    So using this calculator you can easily see why the very good
    advice given to you by "David J. Littleboy" makes sense & see the
    effect of making changes.

    Best wishes, hope this site helps.

    Respectfully, DHB


    "To announce that there must be no criticism of the President,
    or that we are to stand by the President, right or wrong,
    is not only unpatriotic and servile, but is morally treasonable
    to the American public."--Theodore Roosevelt, May 7, 1918
    DHB, Sep 11, 2006
    #19
  20. "ASAAR" <> wrote:
    >
    > Dominated by photon noise? I strongly disagree, unless we're
    > using totally different definitions of words allowing us to talk
    > past each other without realizing it.


    Exactly. You don't understand what the word "dominated" means. "Dominated by
    photon noise" means that the photon noise component is the dominant
    component in the noise, and that other noise components are enough smaller
    than photon noise that they are not significant to the performance of the
    camera.

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Sep 11, 2006
    #20
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