Digital sensors

Discussion in 'Digital Photography' started by cambium, Jan 6, 2005.

  1. cambium

    cambium Guest

    I've been out of touch with new developments for a while - haven't looked at
    the new cameras for a year or so when 6 mp was the general high end. Now 8
    mp seems to be the standard.

    I would be glad of some links to info about what we can expect in the next
    year or two on new digital cameras.

    I am especially interested in the smaller sized sensors (but with higher
    density of mp), that will enable smaller sized cameras with longer telephoto
    lenses.

    Any help appreciated.
     
    cambium, Jan 6, 2005
    #1
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  2. cambium wrote:
    > I've been out of touch with new developments for a while - haven't

    looked at
    > the new cameras for a year or so when 6 mp was the general high end.

    Now 8
    > mp seems to be the standard.
    >
    > I would be glad of some links to info about what we can expect in the

    next
    > year or two on new digital cameras.
    >
    > I am especially interested in the smaller sized sensors (but with

    higher
    > density of mp), that will enable smaller sized cameras with longer

    telephoto
    > lenses.


    Since you mention smaller sized sensors, Samsung announced a 5MP phone
    camera.
    http://www.dpreview.com/news/0410/04102001samsung_schs250.asp
    - Siddhartha
     
    Siddhartha Jain, Jan 6, 2005
    #2
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  3. cambium

    cambium Guest

    That is cool. I'm all for the 'all in one' approach - I want my computer,
    phone, camera, fax, internet etc. etc. to come in one small package - I
    might even consider an implant if I could turn it off if I want to... :)

    But for now I'm intrested in buying a camera - looking at the Coolpix 8800.
    But as usual with this kind of decision, I don't want to buy something that
    is going to be 'outgraded' in a few months. If it is likely to be about as
    good as it gets (in the price range) for a year or so, I'll go for it.






    "Siddhartha Jain" <> wrote in message
    news:...
    > cambium wrote:
    > > I've been out of touch with new developments for a while - haven't

    > looked at
    > > the new cameras for a year or so when 6 mp was the general high end.

    > Now 8
    > > mp seems to be the standard.
    > >
    > > I would be glad of some links to info about what we can expect in the

    > next
    > > year or two on new digital cameras.
    > >
    > > I am especially interested in the smaller sized sensors (but with

    > higher
    > > density of mp), that will enable smaller sized cameras with longer

    > telephoto
    > > lenses.

    >
    > Since you mention smaller sized sensors, Samsung announced a 5MP phone
    > camera.
    > http://www.dpreview.com/news/0410/04102001samsung_schs250.asp
    > - Siddhartha
    >
     
    cambium, Jan 6, 2005
    #3
  4. cambium

    Stacey Guest

    cambium wrote:

    > But as usual with this kind of decision, I don't want to buy
    > something that
    > is going to be 'outgraded' in a few months.


    Then don't buy a digital camera.


    > If it is likely to be about
    > as good as it gets (in the price range) for a year or so, I'll go for it.
    >



    That isn't likely to happen.

    --

    Stacey
     
    Stacey, Jan 7, 2005
    #4
  5. cambium

    Guest

    There is a downside to the smaller sensor. A given lens f/number
    collects only so many photons per square mm on the focal plane. Given
    two sensors, each with the same number of pixels, the smaller sensor
    then gathers fewer photons per pixel, increasing noise in image. The
    result is you need either lower f/# lenses or longer exposure.
     
    , Jan 7, 2005
    #5
  6. cambium

    cambium Guest

    I know what you mean, but then it has been possible to find the plateau that
    does stay current for longer that average - for example my OLY C-2100UZ. It
    is out of date now, but it was ahead of its time for a few years in many
    ways. Even now it is no slouch, but not enough resolution.

    Still, a person will never find anthing if they don't look.




    "Stacey" <> wrote in message
    news:...
    > cambium wrote:
    >
    > > But as usual with this kind of decision, I don't want to buy
    > > something that
    > > is going to be 'outgraded' in a few months.

    >
    > Then don't buy a digital camera.
    >
    >
    > > If it is likely to be about
    > > as good as it gets (in the price range) for a year or so, I'll go for

    it.
    > >

    >
    >
    > That isn't likely to happen.
    >
    > --
    >
    > Stacey
     
    cambium, Jan 7, 2005
    #6
  7. cambium

    cambium Guest

    I wonder about this. Relative to any pixel size, photons are orders of
    magnitudes smaller, and even in low light they come in huge numbers. Do you
    have any references on this so I could understand it better? My gut feeling
    is that the supply of photons in any situation is the least of our worries.
    Rather it is the sensitivity of our sensors that needs work.


    <> wrote in message
    news:...
    > There is a downside to the smaller sensor. A given lens f/number
    > collects only so many photons per square mm on the focal plane. Given
    > two sensors, each with the same number of pixels, the smaller sensor
    > then gathers fewer photons per pixel, increasing noise in image. The
    > result is you need either lower f/# lenses or longer exposure.
    >
     
    cambium, Jan 7, 2005
    #7
  8. cambium

    Matt Ion Guest

    wrote:

    > There is a downside to the smaller sensor. A given lens f/number
    > collects only so many photons per square mm on the focal plane. Given
    > two sensors, each with the same number of pixels, the smaller sensor
    > then gathers fewer photons per pixel, increasing noise in image. The
    > result is you need either lower f/# lenses or longer exposure.


    Not entirely correct. The type of sensor and its light sensitivity is a
    factor as well.
     
    Matt Ion, Jan 8, 2005
    #8
  9. cambium

    Guest

    Surprisingly, the number of photons per unit time is NOT that great in
    very low light. In modern night vision scopes at high gain you can see
    the sparkle. Almost all good electro-optics texts discuss photon
    noise. One that I have always liked was in the Infrared Handbook
    published by IRIA.

    That said, there is an old quote that is of interest. The great guru
    at RCA, Otto Schade, of photomultiplier fame, once said, "I have never
    seen a noisy photon." Now, I am sure that that was actually said
    tongue-in-cheek. What he was really saying is that the actual noise in
    the circuit is electron noise, but clearly the statistical variation in
    the number of photons arriving is a major and unavoidable reason for
    the statistics of the noise in the photo-electron stream.
     
    , Jan 8, 2005
    #9
  10. cambium

    Guest


    >Not entirely correct. The type of sensor and its light sensitivity is

    a
    >factor as well.


    No, the sensor can have NO effect on the arrival of photons at its
    surface prior to them penetrating the sensor. I was speaking of the
    arrival rate of photons, which is completely independent of the
    sensitivity of the sensor, its material, or whatever. True, the noise
    in the resulting electron count does rely on these. However, even if
    you had a device with quantum efficiency of unity, a perfect sensor,
    the number of electrons in any pixel would vary in each exposure as a
    result of the variation in the photon arrival rate.
     
    , Jan 8, 2005
    #10
  11. cambium

    Matt Ion Guest

    wrote:

    >
    >>Not entirely correct. The type of sensor and its light sensitivity is

    >
    > a
    >
    >>factor as well.

    >
    >
    > No, the sensor can have NO effect on the arrival of photons at its
    > surface prior to them penetrating the sensor. I was speaking of the
    > arrival rate of photons, which is completely independent of the
    > sensitivity of the sensor, its material, or whatever. True, the noise
    > in the resulting electron count does rely on these.


    Yes. You said, specifically, "Given two sensors, each with the same
    number of pixels, the smaller sensor then gathers fewer photons per
    pixel, increasing noise in image."

    Would a sensor with half the area but four times the sensitivity not
    have less noise than the larger but less sensitive sensor? No it
    doesn't collect as many photons, but I was responding to your claims
    about NOISE, and the quality and/or sensitivity of the pickup itself
    DOES become a factor in that.


    However, even if
    > you had a device with quantum efficiency of unity, a perfect sensor,
    > the number of electrons in any pixel would vary in each exposure as a
    > result of the variation in the photon arrival rate.
    >
     
    Matt Ion, Jan 9, 2005
    #11
  12. "Matt Ion" <> wrote in message
    news:vVgEd.34749$Xk.21399@pd7tw3no...
    SNIP
    > Would a sensor with half the area but four times the sensitivity not
    > have less noise than the larger but less sensitive sensor?


    Most sensors have similar sensitivity. There may be differences due to
    filters used and on chip support circuitry and microlenses, but the
    silicon is basically the same. The differences will usually be within
    one stop (a factor 2) for digicams.

    Bart
     
    Bart van der Wolf, Jan 10, 2005
    #12
  13. cambium

    Guest

    The photon noise would STILL increase. The senstivity is a factor in
    the OVERALL noise, but at the limit, photon noise will be by
    definition the important factor. As it is, the basic senstivity of
    silicon CCD chips is about 40% of perfect, so we cannot expect a
    doubling of the quantum efficiency.

    Of course, there are more sources of noise than photon noise, so if the
    camera is badly limited by, say, amplifier noise, then yes, it would
    have lower noise if better circuitry were added. But if camera is
    already sensitive enough that photon noise is a major factor, (and it
    will be with very dark exposures with many current cameras), then a
    smaller sensor will be a noisier one.

    One factor, however, is lens relative aperture. The photon noise is
    affected by lens f/#, so two cameras with same chip and electronics,
    but one has lower f/# lens, that camera will show lower photon noise.
     
    , Jan 10, 2005
    #13
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