A few technical question

Discussion in 'Digital Photography' started by Bj?rn Keil, Nov 24, 2003.

  1. Bj?rn Keil

    Bj?rn Keil Guest

    Hi,
    would you please answer me a few technical questions about digital
    cameras. I want to bid for one on ebay soon, but unfortunatly there is
    a great discrepance between I want, I need and I can efford, so I need
    to know more details to decide how much I can offer for what:

    1. There are a lot of cameras that can vary the exposure time, but
    only do this autimatically. The CCD of a camera consists of a photo
    diode matrix, and a photo diode generates voltage or it does not, no
    matter how long one waits, or am I wrong? Since you can't vary it
    manually you can't use it to generate effect when photographing moving
    objects, so what is it good for?

    2. If a camera has stiff lenses, how does it focus? With the width of
    the shutter opening? And how do macro functions work then?

    3. How sensible are CCDs to long time usage? If a camera has been used
    for year and has not fallen down or something, is the CCD of a typical
    brand camera as good as new or should you expect, that one or two
    percent of the CCD is no more working correctly?

    4. What is white balance actually? If it's only automatic, does that
    mean the camera on the wall should, because it's the brightest spot it
    can find, the it seems a bit yellow in the current light?

    5. What is a good resolution to give to a photo laboratory if you want
    to have sharp images without blurring percebtible blurring if you hold
    at 30 - 50 cm (1 - 1.5 ft.)? 720 dpi?

    6. Many cameras offer features like interpolation or digital zoom. I
    guess it's better to not use such features and manipulate the image on
    a PC or Mac afterwards if I really have to, isn't it?

    So that's all for now. If you think I forgot to ask the one really
    important question, you might consider it asked. Thanks for help.

    Bye
    Björn
     
    Bj?rn Keil, Nov 24, 2003
    #1
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  2. "Bj?rn Keil" <> wrote in message
    news:...
    > Hi,
    > would you please answer me a few technical questions about digital
    > cameras. I want to bid for one on ebay soon, but unfortunatly there is
    > a great discrepance between I want, I need and I can efford, so I need
    > to know more details to decide how much I can offer for what:
    >
    > 1. There are a lot of cameras that can vary the exposure time, but
    > only do this autimatically. The CCD of a camera consists of a photo
    > diode matrix, and a photo diode generates voltage or it does not, no
    > matter how long one waits, or am I wrong? Since you can't vary it
    > manually you can't use it to generate effect when photographing moving
    > objects, so what is it good for?


    Go for a camera that gives you the choice of overriding the automatic
    settings. It is common.
    >
    > 2. If a camera has stiff lenses, how does it focus? With the width of
    > the shutter opening? And how do macro functions work then?


    The lenses focus just like lenses in film cameras. The way it works
    automatically is a bit different. A digicam uses information from the
    sensor to set the focus' a film camera uses an infrared beam, much like
    ladar (radar with light instead of microwaves.)
    >
    > 3. How sensible are CCDs to long time usage? If a camera has been used
    > for year and has not fallen down or something, is the CCD of a typical
    > brand camera as good as new or should you expect, that one or two
    > percent of the CCD is no more working correctly?


    The sensor should not degrade with time. But if you point the camera at the
    sun, you could cause damage.
    >
    > 4. What is white balance actually? If it's only automatic, does that
    > mean the camera on the wall should, because it's the brightest spot it
    > can find, the it seems a bit yellow in the current light?


    It adjusts the color response according to the ambient light. It is a
    software function.

    >
    > 5. What is a good resolution to give to a photo laboratory if you want
    > to have sharp images without blurring percebtible blurring if you hold
    > at 30 - 50 cm (1 - 1.5 ft.)? 720 dpi?


    250 to 300 pixels per inch. B.t.w., dpi refers to the dots of ink that a
    printer puts down. Pictures are sized in pixels.
    >
    > 6. Many cameras offer features like interpolation or digital zoom. I
    > guess it's better to not use such features and manipulate the image on
    > a PC or Mac afterwards if I really have to, isn't it?
    >

    You are right on that.

    > So that's all for now. If you think I forgot to ask the one really
    > important question, you might consider it asked. Thanks for help.
    >
    > Bye
    > Björn
     
    Marvin Margoshes, Nov 24, 2003
    #2
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  3. Bj?rn Keil

    Andy Hewitt Guest

    Marvin Margoshes <> wrote:

    > > 1. There are a lot of cameras that can vary the exposure time, but
    > > only do this autimatically. The CCD of a camera consists of a photo
    > > diode matrix, and a photo diode generates voltage or it does not, no
    > > matter how long one waits, or am I wrong? Since you can't vary it
    > > manually you can't use it to generate effect when photographing moving
    > > objects, so what is it good for?

    >
    > Go for a camera that gives you the choice of overriding the automatic
    > settings. It is common.


    Indeed, a lot also have very simple focus and metering locks too - even
    in auto mode.

    > > 2. If a camera has stiff lenses, how does it focus? With the width of
    > > the shutter opening? And how do macro functions work then?

    >
    > The lenses focus just like lenses in film cameras. The way it works
    > automatically is a bit different. A digicam uses information from the
    > sensor to set the focus' a film camera uses an infrared beam, much like
    > ladar (radar with light instead of microwaves.)


    Nope, the new Z1 certainly uses an infrared beam.


    --
    Andy Hewitt ** FAF#1, OSOS#5 - BMW K100RS 8v, Honda Concerto 16v
    Windows free zone (Mac G3)
    <http://homepage.ntlworld.com/ahewitt/index.htm> (last update 12.02)
     
    Andy Hewitt, Nov 24, 2003
    #3
  4. Bj?rn Keil

    Bj?rn Keil Guest

    Thanks for your answers.

    > > 4. What is white balance actually? If it's only automatic, does that
    > > mean the camera on the wall should, because it's the brightest spot it
    > > can find, the it seems a bit yellow in the current light?

    >
    > It adjusts the color response according to the ambient light. It is a
    > software function.


    hmm... I thought it would be a way to set threshold value for the ad
    converter. If it's a software function it falls into the category:
    "You better do this your computer."
     
    Bj?rn Keil, Nov 25, 2003
    #4
  5. Bj?rn Keil

    Don Stauffer Guest

    A CCD chip is not what is ordinarily considered a photodiode matrix,
    where each photodetector is individually addressable and gives a voltage
    output.

    Rather, in a CCD each detector supplies current to charge a tiny
    capacitor. Q=ixdt, so the voltage that builds up on each capacitor
    depends directly on exposure time. When the charging is complete, the
    capacitors are then dumped to the readout circuitry.

    Bj?rn Keil wrote:
    >
    > Hi,
    > would you please answer me a few technical questions about digital
    > cameras. I want to bid for one on ebay soon, but unfortunatly there is
    > a great discrepance between I want, I need and I can efford, so I need
    > to know more details to decide how much I can offer for what:
    >
    > 1. There are a lot of cameras that can vary the exposure time, but
    > only do this autimatically. The CCD of a camera consists of a photo
    > diode matrix, and a photo diode generates voltage or it does not, no
    > matter how long one waits, or am I wrong? Since you can't vary it
    > manually you can't use it to generate effect when photographing moving
    > objects, so what is it good for?
    >
    > 2. If a camera has stiff lenses, how does it focus? With the width of
    > the shutter opening? And how do macro functions work then?
    >
    > 3. How sensible are CCDs to long time usage? If a camera has been used
    > for year and has not fallen down or something, is the CCD of a typical
    > brand camera as good as new or should you expect, that one or two
    > percent of the CCD is no more working correctly?
    >
    > 4. What is white balance actually? If it's only automatic, does that
    > mean the camera on the wall should, because it's the brightest spot it
    > can find, the it seems a bit yellow in the current light?
    >
    > 5. What is a good resolution to give to a photo laboratory if you want
    > to have sharp images without blurring percebtible blurring if you hold
    > at 30 - 50 cm (1 - 1.5 ft.)? 720 dpi?
    >
    > 6. Many cameras offer features like interpolation or digital zoom. I
    > guess it's better to not use such features and manipulate the image on
    > a PC or Mac afterwards if I really have to, isn't it?
    >
    > So that's all for now. If you think I forgot to ask the one really
    > important question, you might consider it asked. Thanks for help.
    >
    > Bye
    > Björn


    --
    Don Stauffer in Minnesota

    webpage- http://www.usfamily.net/web/stauffer
     
    Don Stauffer, Nov 25, 2003
    #5
  6. Bj?rn Keil

    Bjoern Keil Guest

    Wow,
    thanks, that's a good answer. I guess Q=ixdt means Q is the integral of
    x by the differential of t, where Q is Voltage x is light sensivity and
    t is time, is it?
    Does somebody now a place to look for an understandable, good
    description in the Internet, that explains these thing more detailed?

    Don Stauffer wrote:
    > A CCD chip is not what is ordinarily considered a photodiode matrix,
    > where each photodetector is individually addressable and gives a voltage
    > output.
    >
    > Rather, in a CCD each detector supplies current to charge a tiny
    > capacitor. Q=ixdt, so the voltage that builds up on each capacitor
    > depends directly on exposure time. When the charging is complete, the
    > capacitors are then dumped to the readout circuitry.
    >
    > Bj?rn Keil wrote:
    >
    >>Hi,
    >>would you please answer me a few technical questions about digital
    >>cameras. I want to bid for one on ebay soon, but unfortunatly there is
    >>a great discrepance between I want, I need and I can efford, so I need
    >>to know more details to decide how much I can offer for what:
    >>
    >>1. There are a lot of cameras that can vary the exposure time, but
    >>only do this autimatically. The CCD of a camera consists of a photo
    >>diode matrix, and a photo diode generates voltage or it does not, no
    >>matter how long one waits, or am I wrong? Since you can't vary it
    >>manually you can't use it to generate effect when photographing moving
    >>objects, so what is it good for?
    >>
    >>2. If a camera has stiff lenses, how does it focus? With the width of
    >>the shutter opening? And how do macro functions work then?
    >>
    >>3. How sensible are CCDs to long time usage? If a camera has been used
    >>for year and has not fallen down or something, is the CCD of a typical
    >>brand camera as good as new or should you expect, that one or two
    >>percent of the CCD is no more working correctly?
    >>
    >>4. What is white balance actually? If it's only automatic, does that
    >>mean the camera on the wall should, because it's the brightest spot it
    >>can find, the it seems a bit yellow in the current light?
    >>
    >>5. What is a good resolution to give to a photo laboratory if you want
    >>to have sharp images without blurring percebtible blurring if you hold
    >>at 30 - 50 cm (1 - 1.5 ft.)? 720 dpi?
    >>
    >>6. Many cameras offer features like interpolation or digital zoom. I
    >>guess it's better to not use such features and manipulate the image on
    >>a PC or Mac afterwards if I really have to, isn't it?
    >>
    >>So that's all for now. If you think I forgot to ask the one really
    >>important question, you might consider it asked. Thanks for help.
    >>
    >>Bye
    >>Björn

    >
    >
     
    Bjoern Keil, Nov 25, 2003
    #6
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