CCD Vs CMOS Sensors

Discussion in 'Digital Photography' started by Dick Campbell, Jan 3, 2004.

  1. Any thoughts on how they compare?

    Any difference in dyanamic range for example?

    A few things I can think of are:-

    1. The larger sensors seem to be CMOS so I assume that large CCDs are more
    expensive to make.
    2. My DSLR has a CMOS sensor (probably due to item 1), it does not have live
    preview and cannot take movies (not that I mind). I an not sure whether this
    is a CMOS or SLR issue.
    3. The battery life on my DLSR is very good, possbly due to the use of CMOS
    (lower power usage perhaps?) but also possibly due to the fact there is no
    live preview.

    That's my 2 cents worth, I am not even really sure of my facts though.

    Dick Campbell
     
    Dick Campbell, Jan 3, 2004
    #1
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  2. Good try :)

    Nope - you are guesses are mostly wrong.

    Photographic sensors of any quality are mostly CCD.

    There are two exceptions. Canon make CMOS sensors and
    so do Foveon.

    CMOS sensors are commonly considered too noisy and slow.
    On the other hand - they are less expensive. You can also
    put complex functionality on a CMOS chip.

    So - why do Canon make their DSLR sensors in CMOS, and
    doing so with some success? Good question :) I don't
    really know. What I have heard is that Canon uses the
    possibility to add complex functionality to (very
    succesfully) compensate for the higher noise. If that
    is true, I don't know. Sounds reasonable though.

    NOTE: really fast cameras are still CCD. The Canon CMOS
    cameras are not the fastest DSLR on the market.


    /Roland
     
    Roland Karlsson, Jan 4, 2004
    #2
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  3. Dick Campbell

    Marli Guest

    Canon have just developed the CMOS sensor to the point of being as good as a
    CCD sensor, and probably better in most cases.
     
    Marli, Jan 4, 2004
    #3
  4. Dick Campbell

    Michael Guest

    Hi,
    This is true. It's a more widely used technology.
    Nikon has started using a technology called JFET, which is somewhat similar
    to CMOS but using fewer transistors on the sensor.
    Actually CMOS sensors have a lot of benefits over CCD. They use much less
    power (something like 10x), an image can be read out of the sensor many
    times faster than from a CCD sensor, and the design itself allows for noise
    cancellation do be done directly at each fotosite. The resulting image is
    very clean as evidenced by cameras such as the Canon D30 and it's later
    replacements.

    You can also read out parts of an image from a CMOS sensor. You can't do
    that with CCD.

    I recommend the following article on the D30 for some reference information
    on CCD versus CMOS:

    http://www.imaging-resource.com/PRODS/D30/D30A4.HTM
    CMOS isn't more noisy than CCD. Also, Canon use a design where their CMOS
    sensors are very large - some are full frame, and because each fotosite is
    so much bigger than on a CCD, noise becomes much less apparent.
    What do you mean by fast. Camera speed is usually a lens issue.

    /Michael
     
    Michael, Jan 4, 2004
    #4
  5. Dick Campbell

    Michael Guest

    Hi,
    Canon's CMOS sensor has been better (meaning less noisy) than any comparable
    CCD sensor I know of since the D30.

    /Michael
     
    Michael, Jan 4, 2004
    #5
  6. Dick Campbell

    jriegle Guest

    It is both a sensor and the SLR design issue. Read here about the sensor:
    http://www.dpreview.com/learn/Glossary/Camera_System/Sensor_01.htm
     
    jriegle, Jan 4, 2004
    #6
  7. Dick Campbell

    Michael Guest

    Hi,
    CMOS is cheaper to make, mainly due manufacturing differences. CCD requires
    specialized equipment whereas CMOS is so widely used in other types of
    electronics that most production facilities can manufacture CMOS sensors
    without investing in expensive new equipment. This means more supply and so
    lower costs.
    This is an SLR issue - it has nothing to do with the type of sensor being
    used. I know of only one SLR which can give you a live preview, and that is
    the Olympus E-10.

    The SLR concept involves a mirror or prism mounted in front of the sensor,
    allowing you to see "through the lens" when you look through the viewfinder.
    This mechanism normally blocks light from reaching the sensor.

    The satisfying little click you hear when you take a picture with an SLR is
    actually the mirror flipping up to allow light to pass directly to the
    sensor.
    Both are true - LCD displays eat tons of battery and CMOS is up to 10x more
    efficient with respect to power consumption, compared to CCD.

    Check out http://www.imaging-resource.com/PRODS/D30/D30A4.HTM for some more
    in-depth information on the differences between CMOS and CCD.

    /Michael
     
    Michael, Jan 4, 2004
    #7
  8. The main difference is that CCDs are specialized chips, even though they are
    fabricated in silicon. CMOS is built from traditional transistor
    fabrication, so they adhere's to Moore's law and double in power every X
    months, etc. Foveon is way ahead of Canon in terms of chip power and
    fabrication. When Dick Merrill joined the team he brought with him the
    awsome manufacturing prowess of NSC's 0.18 micron South Portland plant,
    which is where the Pro 10M is made now.

    The interesting thing about CMOS is that peripheral electronics can be and
    are intergrated into the sensor itself, giving it on-chip processing power.
    The 10.3MP chip in the SD9 and updated for the SD10 is probably equivalent
    to about a Pentium 4 in terms of the number of transitors it has to work
    with, somewhere between 50 and 100 million (I'm guessing based on the
    original 16MP Foveon prototype, which was announced as having 70 million
    transitiors, far more than a then state-of-the-art Pentium 3). This gives
    CMOS sensors the ability to do an incredible amount of parallel work right
    on the sensor itself, which has the potential to do all sorts of image
    processing magic given enough processing power. Carver Mead liken's the
    current Foveon chip to the human eye, which does a significant amount of
    processing before shuffling the data off to the brain. Dick Merrill has
    hinted at all sorts of future possibilities like electronic focus and CA
    reduction on the sensor itself.

    Point being, the sky is the limit for CMOS optical sensors, even though the
    technology is still immature.
    Definitely. CMOS chips are manufactured like any other high volume silicon.
    National Semiconductor said they could field disposable digital cameras
    based on a verision of the Foveon CMOS at competive prices with film based
    disposables.

    NSC's large scale manufacturing ability is a key reason the 10.3MP Sigma
    DLSRs cost so much less than even prosumer digital cameras. Expect prices
    to drop dramatically on Foveon based cameras in the future. Sigma's SD
    series DSLRs certainly have the potential to sell in the same range as their
    film based SLRs, $100-$300.
    It's an SLR issue. If anything CMOS are better suited to video due to
    inherent processing power and increasing speed.
    CMOS sensors are lower power too, and will continue to scale in accordance
    with Moores law. This makes them suitable for very small/light/cheap mobile
    applications as well.
     
    George Preddy, Jan 4, 2004
    #8
  9. CCD IMAGES..... Look like digital and CMOS images Look like Photos
    ..............so

    Bob
     
    Bob Pattinson, Jan 4, 2004
    #9
  10. Thanks George,

    Very informative. Actually I think I had heard before that CMOS has much
    more inherent onboard computing power than CCD.

    I have also gained an understanding that Fovean has a built in advantage in
    that it senses all three colours at one receptor site.

    I chose the Canon 300D on price and don't regret that decision but I can see
    that a 3 MP Fovean sensor can be better than "half as good" as a 6 MP Canon
    sensor. Not that any comparison can be that simplistic.

    Over time my main investment will be lenses so hopefully by the time I need
    to replace the camera body, the choice will be obvious.

    Dick Campbell
     
    Dick Campbell, Jan 4, 2004
    #10
  11. Now if an expert would post something it would be even more interesting.
    It'll be very interesting to see where CMOS goes as chip power grows. One
    reason Foveon is good for everyone is that its competion for Canon CMOS and
    competition is inherently good. I think there are a few others out there
    waiting in the wings.
    The 300D is an excellent camera. A lot of people think I don't like it and
    that's actually quite wrong. It has strengths and weaknesses just like
    Foveon, the two actually misalign very well, so if you like/need the
    strengths of one, the other makes little sense.
    So many people underestimate the cost and importance of good lenses. I
    researched it a lot and I totally inderestimated how much I would wind up
    spending on lenses. How bout you?
     
    George Preddy, Jan 4, 2004
    #11
  12. Dick Campbell

    Azzz1588 Guest

    Well seeing as to you an $80 sigma lens is quality, I can see why.


    You just need to flip more burgers at MacDonalds.
    Than maybe you can afford a decent lens sometime................




















    "Only a Gentleman can insult me, and a true Gentleman never will..."
     
    Azzz1588, Jan 4, 2004
    #12
  13. Dick Campbell

    Bill Hilton Guest

    Bill Hilton, Jan 4, 2004
    #13
  14. Dick Campbell

    Lionel Guest

    Kibo informs me that (Bill Hilton) stated that:
    Interesting article. However, I must take issue with one statement:
    ----
    "CCDs have been mass-produced for over 25 years whereas CMOS technology
    has only just begun the mass production phase."
    ----
    As stated, that is incorrect. In fact, CMOS technology has been
    mass-produced for more than 20 years. I suspect that what they meant to
    say was that: " CMOS *imaging* technology has only just begun the mass
    production phase", which is quite correct, but gives their comments a
    somewhat different slant. CMOS design is a mature science, it's only the
    imaging side of it that needs to catch up with CCDs. I doubt very much
    that it'll take more than a few years.
     
    Lionel, Jan 4, 2004
    #14
  15. Dick Campbell

    Don Coon Guest

    Bunch of nothing -- other than "stay tuned!"
     
    Don Coon, Jan 4, 2004
    #15
  16. Dick Campbell

    jriegle Guest

    Wrong. Please see my other post.
     
    jriegle, Jan 4, 2004
    #16
  17. Dick Campbell

    Chris Brown Guest

    That's *re*view, not *pre*view.
     
    Chris Brown, Jan 4, 2004
    #17
  18. Dick Campbell

    Mark Johnson Guest

    Instead of x-view, or nex-view, or?

    I wondered if he meant by that he wasn't able to see what he shot
    after he shot it. Do you think he can't see what he shot before he
    shoots it?
     
    Mark Johnson, Jan 4, 2004
    #18
  19. So far I have spent less on lenses than on the camera but I am fairly sure
    that one day the position will be reversed. By then I will be locked into
    Canon lenses of course so it will be a question of what sort of Canon (or
    Canon compatible) body is available in say 5 years time. Perhaps Canon will
    go Fovean eventually perhaps not. I imagine they would only do it if Fovean
    become universally accepted as the way to go.

    As for the 300D, I am very happy with it. Whether 6MP CMOS is equal to or
    better than 3 MP Fovean doesn't concern me, I like the pictures I am getting
    which is what matters. See http://www.pbase.com/dickcampbell19/sydney for a
    couple of examples. Note that the "orignal" image is straight out of the
    camera, about 5 MB.
     
    Dick Campbell, Jan 4, 2004
    #19
  20. Dick Campbell

    Michael Guest

    Hi,

    (regarding live previews)
    Your other post refers to a clarification page on dpreview.com, where it is
    stated that CCD's can be controlled by software and so do not require
    mechanical shutters. You are in a sense correct that the sensor type does
    matter with respect to live previews, because you need to use CCD technology
    to obtain the live image in the first place.

    However, the SLR configuration uses a prism or a mirror mounted in front of
    the sensor to provide the TTL image for the viewfinder, so it doesn't really
    matter what sensor sits behind it - the mirror makes live previews
    impossible either way. As such my statement was correct.

    Some SLR's obtain the TTL viewfinder image directly from the sensor, in
    which case a mirror is not needed at all. But I have heard people argue that
    such a camera isn't an SLR to begin with. And then it gets kind of religious
    ... :)

    By the way, you may want to consider not quoting everything next time you
    reply. It's not very helpful.

    /Michael
     
    Michael, Jan 4, 2004
    #20
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