How does it work ?

Discussion in 'Digital Photography' started by x@x.com, Oct 6, 2006.

  1. Guest

    I've got a really basic question: Where does the image you get in the LCD
    and EVF come from ?

    Does it come from the sensor ?
    If so, how does the shutter speed works, do they close the shutter, discharge
    the sensor, and re-open the sensor for the appropriate time ?


    Thanks.
    , Oct 6, 2006
    #1
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  2. Guest

    > I've got a really basic question: Where does the image you get in the LCD
    > and EVF come from ?
    > Does it come from the sensor ?


    Usually directly from the sensor.

    > If so, how does the shutter speed works, do they close the shutter, discharge
    > the sensor, and re-open the sensor for the appropriate time ?


    There are no more shutters in many of today's digital camera. With
    electronic viewfinders, the sensor is always on. When you push the
    shutter button, it saves the image to storage (simplified version).
    Technically, it's a lot more complex with image stabilization
    synchronization, reading out the sensor, etc. But there are generally
    no more shutters . . . unles you have a digital SLR that doesn't have
    full-time electronic viewfinder.

    Chieh
    --
    Camera Hacker - http://www.CameraHacker.com/
    , Oct 6, 2006
    #2
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  3. D Russell Guest

    wrote:

    >> I've got a really basic question: Where does the image you get in the LCD
    >> and EVF come from ?
    >> Does it come from the sensor ?

    >
    > Usually directly from the sensor.
    >
    >> If so, how does the shutter speed works, do they close the shutter,
    >> discharge the sensor, and re-open the sensor for the appropriate time ?

    >
    > There are no more shutters in many of today's digital camera. With
    > electronic viewfinders, the sensor is always on. When you push the
    > shutter button, it saves the image to storage (simplified version).
    > Technically, it's a lot more complex with image stabilization
    > synchronization, reading out the sensor, etc. But there are generally
    > no more shutters . . . unles you have a digital SLR that doesn't have
    > full-time electronic viewfinder.
    >
    > Chieh
    > --
    > Camera Hacker - http://www.CameraHacker.com/



    This kinda brings up an interesting question, well to my mind at least.

    With a DSLR you've got a mirror still, usually, at least as I understand it,
    which redirects the light from the lens up into the eyepiece. This was
    always seen as much better than a small compact film camera because you
    were actually seeing through the lens hence had a better idea of what you'd
    photograph. These days an awful lot of the compact cameras now feed their
    viewscreen direct from the CCD which will actually be taking the picture.
    Does this mean it will now give you a better representation of what you'll
    photograph ?

    Now I know that's heresy to the pro-DSLR mob, so please take it with a pinch
    of salt, and if you don't even get far enough to actually read this line,
    well then you're hardly worth responding to I guess.

    D
    D Russell, Oct 9, 2006
    #3
  4. D Russell wrote:
    snip
    >
    > This kinda brings up an interesting question, well to my mind at least.
    >
    > With a DSLR you've got a mirror still, usually, at least as I understand it,
    > which redirects the light from the lens up into the eyepiece. This was
    > always seen as much better than a small compact film camera because you
    > were actually seeing through the lens hence had a better idea of what you'd
    > photograph. These days an awful lot of the compact cameras now feed their
    > viewscreen direct from the CCD which will actually be taking the picture.
    > Does this mean it will now give you a better representation of what you'll
    > photograph ?
    >
    > Now I know that's heresy to the pro-DSLR mob, so please take it with a pinch
    > of salt, and if you don't even get far enough to actually read this line,
    > well then you're hardly worth responding to I guess.
    >
    > D


    No. First of all, a good optical grade mirror produces less loss of
    image quality than the eye can detect, so the reflex view is certainly
    not degraded.

    Secondly, the lens MAY provide a higher resolution picture (if it is a
    good lens) than some of the lower resolution chips. That is, below a
    given number of MP, the chip is the limit on resolution. That is
    usually less than eye resolution.

    Most importantly, the LCD screen is FAR lower resolution than typical
    imaging chips even in low cost P&S. Most screens are well below 1MP.

    I find them completely inadequate for manual focus, for instance.
    Don Stauffer in Minnesota, Oct 9, 2006
    #4
  5. Guest

    Don Stauffer in Minnesota <> wrote:

    > D Russell wrote:


    >> With a DSLR you've got a mirror still, usually, at least as I understand it,
    >> which redirects the light from the lens up into the eyepiece. This was
    >> always seen as much better than a small compact film camera because you
    >> were actually seeing through the lens hence had a better idea of what you'd
    >> photograph. These days an awful lot of the compact cameras now feed their
    >> viewscreen direct from the CCD which will actually be taking the picture.
    >> Does this mean it will now give you a better representation of what you'll
    >> photograph ?


    This is sort of what I'm getting at, but wanted to confirm that the image on
    the LCDs were indeed coming from the sensor. I still haven't got an answer
    about the fact that sensors heat up, and therefore should not be exposed for
    too long. Is this true or a myth ?

    > Secondly, the lens MAY provide a higher resolution picture (if it is a
    > good lens) than some of the lower resolution chips. That is, below a
    > given number of MP, the chip is the limit on resolution. That is
    > usually less than eye resolution.


    > Most importantly, the LCD screen is FAR lower resolution than typical
    > imaging chips even in low cost P&S. Most screens are well below 1MP.


    > I find them completely inadequate for manual focus, for instance.


    Hmmm... Good point. But you'd think that ultimately they'll be able to produce
    really good EVF with super high resolution (same as sensor), and finally get
    rid of the mirror and prism. What a saving on space and weight ! And no more
    vibration from the mirror either.

    I wonder how many years away we're from this.
    , Oct 9, 2006
    #5
  6. Guest

    wrote:
    > > I've got a really basic question: Where does the image you get in the LCD
    > > and EVF come from ?
    > > Does it come from the sensor ?

    >
    > Usually directly from the sensor.
    >
    > > If so, how does the shutter speed works, do they close the shutter, discharge
    > > the sensor, and re-open the sensor for the appropriate time ?

    >
    > There are no more shutters in many of today's digital camera.


    That's not correct, unless you're writing about the absolute bottom of
    the range digicam.
    All digital cameras with an EVF and almost all with a LCD have a
    shutter, it is just open while giving the live preview (the image
    displayed on the EVF or LCD) and closes briefly to flush the sensor
    before taking the exposure for a still image.
    That is what gives the EVF/LCD type digicam a longer shutter lag, even
    if they are set to manual focus and exposure modes.

    > With electronic viewfinders, the sensor is always on. When you push the
    > shutter button, it saves the image to storage (simplified version).


    That may be correct for a movie mode on a digital stills camera, but
    not for normal single exposures on most digicams available today.
    , Oct 10, 2006
    #6
  7. Guest

    D Russell wrote:
    <snip>
    >
    > This kinda brings up an interesting question, well to my mind at least.
    >
    > With a DSLR you've got a mirror still, usually, at least as I understand it,
    > which redirects the light from the lens up into the eyepiece. This was
    > always seen as much better than a small compact film camera because you
    > were actually seeing through the lens hence had a better idea of what you'd
    > photograph. These days an awful lot of the compact cameras now feed their
    > viewscreen direct from the CCD which will actually be taking the picture.
    > Does this mean it will now give you a better representation of what you'll
    > photograph ?
    >
    > Now I know that's heresy to the pro-DSLR mob, so please take it with a pinch
    > of salt, and if you don't even get far enough to actually read this line,
    > well then you're hardly worth responding to I guess.


    The live preview in the EVF or on the LCD of a compact may give a
    better idea of how the exposure will look in regards to overall
    brightness and overall contrast, but the low resolution (typicaly
    640x480 pixels or less) makes them totaly useless for focusing.
    That explains why the upper end of the compacts that have manual
    focusing also have their view magnified (usualy it's the central
    portion of the live preview) when their focus control is operated, but
    this can be almost useless, especialy in low light where it can look
    very blotchy and low cotrast (where a SLR viewfinder could still be
    quite clear and easy to focus with).

    I have (and use) both a Pentax ist-Ds and a Konica-Minolta A200, so I
    do have some experience in both "camps".
    , Oct 10, 2006
    #7
  8. Guest

    wrote:

    > That's not correct, unless you're writing about the absolute bottom of
    > the range digicam.
    > All digital cameras with an EVF and almost all with a LCD have a
    > shutter, it is just open while giving the live preview (the image
    > displayed on the EVF or LCD) and closes briefly to flush the sensor
    > before taking the exposure for a still image.
    > That is what gives the EVF/LCD type digicam a longer shutter lag, even
    > if they are set to manual focus and exposure modes.


    That make sense I guess. So is that a mechanical shutter, or is the CCD
    flushed electronically.

    That definitely explains the delay that the SLR don't seem to get.
    , Oct 10, 2006
    #8
  9. John Turco Guest

    wrote:
    >
    > Don Stauffer in Minnesota <> wrote:


    <edited, for brevity>

    > > Most importantly, the LCD screen is FAR lower resolution than typical
    > > imaging chips even in low cost P&S. Most screens are well below 1MP.

    >
    > > I find them completely inadequate for manual focus, for instance.

    >
    > Hmmm... Good point. But you'd think that ultimately they'll be able to produce
    > really good EVF with super high resolution (same as sensor), and finally get
    > rid of the mirror and prism. What a saving on space and weight ! And no more
    > vibration from the mirror either.
    >
    > I wonder how many years away we're from this.



    Hello,

    I suspect that significantly better EVF's are viable, today, utilizing
    OLED (organic light-emitting diode) displays. Alas, OLED technology has
    been extremely slow, in attempting to gain any sort of a real foothold
    in the consumer electronics industry, as a whole -- thus, I wouldn't
    hold my breath, waiting for OLED-equipped digital cameras to become
    commonplace.


    Cordially,
    John Turco <>
    John Turco, Oct 13, 2006
    #9
  10. I do not own a digicam, but am looking - so I do not know the answer to
    the question that I want to ask: If a digicam had the option of viewing
    by via 'rangefinder', or LED screen, if you turned off the LCD screen,
    could you avoid the sensor/screen flushing delay?

    Rob in Calgary

    wrote:
    > wrote:
    >>> I've got a really basic question: Where does the image you get in the LCD
    >>> and EVF come from ?
    >>> Does it come from the sensor ?

    >> Usually directly from the sensor.
    >>
    >>> If so, how does the shutter speed works, do they close the shutter, discharge
    >>> the sensor, and re-open the sensor for the appropriate time ?

    >> There are no more shutters in many of today's digital camera.

    >
    > That's not correct, unless you're writing about the absolute bottom of
    > the range digicam.
    > All digital cameras with an EVF and almost all with a LCD have a
    > shutter, it is just open while giving the live preview (the image
    > displayed on the EVF or LCD) and closes briefly to flush the sensor
    > before taking the exposure for a still image.
    > That is what gives the EVF/LCD type digicam a longer shutter lag, even
    > if they are set to manual focus and exposure modes.
    >
    >> With electronic viewfinders, the sensor is always on. When you push the
    >> shutter button, it saves the image to storage (simplified version).

    >
    > That may be correct for a movie mode on a digital stills camera, but
    > not for normal single exposures on most digicams available today.
    >
    Robert Charles Young, Dec 30, 2006
    #10
  11. At least one of my film SLR cameras have the ability to 'lock-up' the
    mirror once the shot is prepared for

    Rob in Calgary

    wrote:
    > wrote:
    >>> I've got a really basic question: Where does the image you get in the LCD
    >>> and EVF come from ?
    >>> Does it come from the sensor ?

    >> Usually directly from the sensor.
    >>
    >>> If so, how does the shutter speed works, do they close the shutter, discharge
    >>> the sensor, and re-open the sensor for the appropriate time ?

    >> There are no more shutters in many of today's digital camera.

    >
    > That's not correct, unless you're writing about the absolute bottom of
    > the range digicam.
    > All digital cameras with an EVF and almost all with a LCD have a
    > shutter, it is just open while giving the live preview (the image
    > displayed on the EVF or LCD) and closes briefly to flush the sensor
    > before taking the exposure for a still image.
    > That is what gives the EVF/LCD type digicam a longer shutter lag, even
    > if they are set to manual focus and exposure modes.
    >
    >> With electronic viewfinders, the sensor is always on. When you push the
    >> shutter button, it saves the image to storage (simplified version).

    >
    > That may be correct for a movie mode on a digital stills camera, but
    > not for normal single exposures on most digicams available today.
    >
    Robert Charles Young, Dec 30, 2006
    #11
  12. Robert Charles Young <> writes:
    >I do not own a digicam, but am looking - so I do not know the answer to
    >the question that I want to ask: If a digicam had the option of viewing
    >by via 'rangefinder', or LED screen, if you turned off the LCD screen,
    >could you avoid the sensor/screen flushing delay?


    I think what you're asking is this: If a digicam has an optical viewfinder
    (not a rangefinder, because it doesn't measure distance) and you use
    that for aiming, and you turn off the LCD (not LED) live image display,
    does the camera shoot faster?

    On some Canons, at least, that does indeed seem to be true, particularly
    if you're also in manual focus mode.

    Dave
    Dave Martindale, Dec 30, 2006
    #12
  13. acl Guest

    Dave Martindale wrote:
    > Robert Charles Young <> writes:
    > >I do not own a digicam, but am looking - so I do not know the answer to
    > >the question that I want to ask: If a digicam had the option of viewing
    > >by via 'rangefinder', or LED screen, if you turned off the LCD screen,
    > >could you avoid the sensor/screen flushing delay?

    >
    > I think what you're asking is this: If a digicam has an optical viewfinder
    > (not a rangefinder, because it doesn't measure distance) and you use
    > that for aiming, and you turn off the LCD (not LED) live image display,
    > does the camera shoot faster?
    >
    > On some Canons, at least, that does indeed seem to be true, particularly
    > if you're also in manual focus mode.


    On the other hand, my first digital was (is) a Minolta Z3. This has a
    mode in which it shoots 10 shots per second (and it really does, I
    tested it). Of course, in a low resolution (presumably bandwidth
    limits).
    acl, Dec 30, 2006
    #13
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