DLSR and Pixels

Discussion in 'Digital Photography' started by Eugene, Apr 23, 2009.

  1. Eugene

    Eugene Guest

    DLSR is supposed to be good because the pixel
    is bigger. In the Canon 300D. The pixel size is
    7.4 micron, 6+ megapixels. Now with the Canon 1000D,
    pixel size is 5.7 micron, 10+megapixel. Both has
    the same CCD size of 22.5 x 15mm. Notice the pixel
    size has gone smaller. Wouldn't this defeat the purpose
    of DSLR (Bigger Pixel Rocks)? Has anyone compared
    the quality of the 300D vs 1000D? Which is cleaner?
    Using the same 22.5 x 15mm grid, how small can
    the pixel get (or how large can the megapixels be,
    as they are inversely proportional) before noise would become bad
    enough that it won't be far from
    point&shoot CCDs?

    Eugene, Apr 23, 2009
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  2. Eugene

    Mr. Strat Guest

    Do you have any knowledge of or experience with photography?

    It doesn't look like it.
    Mr. Strat, Apr 23, 2009
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  3. Actually no. dSLRs are good because you can customize them for your
    personal needs with different lenses and other accessories.
    Better light gathering because of larger pixels is a nice added bonus.
    Surprise, surprise. It's called mathematics, you know.
    Not at all, because larger pixel size is nice added bonus, nothing more.

    Jürgen Exner, Apr 23, 2009
  4. Eugene

    Derge Guest

    Well, yes and no. The point of DSLRs isn't that they have big pixels.
    The point is that they have big sensors.

    The notion of "pixel level" noise is a bit of a red herring, since
    ultimately we, as human beings, need to view an image taken with any
    camera at fixed dimensions, whether in print or on the web. The camera
    usually doesn't determine what those dimensions are: We do! If you're
    sending snapshots to your grandmother, for instance, they're only
    going to be 800x600 JPEGs, no matter what camera took them. A
    comparison at that size would give you similar pictures. If anything,
    the images from the EOS 1000D would be *less* noisy *because* it has
    smaller pixels, which means lower read noise per unit area.

    You obviously understand the relationship between pixel size and
    noise. The other edge of the sword is this: Anything "lost" by using
    smaller pixels can be reclaimed by resizing the larger image in
    Photoshop. This only works in one direction, obviously. Smaller pixels
    give us a choice.
    Derge, Apr 23, 2009
  5. Eugene

    Eugene Guest

    What? But pixels are sensors. What you talking about?
    Or you mean bigger pixels? How can smaller pixels be less noisy?

    Eugene, Apr 23, 2009
  6. Eugene wrote:
    If you are viewing the complete image, is it better that it be made up of
    5MP or 10MP, given that each of the 10MP pixels will be smaller, slightly
    noisier, but that the 10MP image will be a little sharper?

    Perhaps the optimum varies for different images, and some shots will
    benefit more from the greater sharpness, and others from the lower noise?

    Also, bear in mind that a more recent camera may have slight improvements,
    resutling in a better signal-to-noise ratio for each pixel.

    There isn't a single answer, you see.

    David J Taylor, Apr 23, 2009
  7. Eugene

    Doug Jewell Guest

    All else being equal, bigger pixel size would be lower
    noise. But like many things, all else isn't equal. Modern
    cameras have improved sensor design, including less sensor
    area dedicated to support electronics, so the actual
    sensitive area hasn't shrunk by the same proportion that the
    MP increase would indicate. Additionally support circuitry
    has improved, post-processing (both in and out of camera)
    has improved, so once again the performance doesn't scale
    linearly with MP. While I haven't done a direct comparison,
    and I have a 450D not a 1000D, the "vibe" I get from my 12MP
    450D is that it is only slightly noisier than the older
    lower MP cameras. In some cases maybe less noisy. The
    increase in noise is also offset by a dramatic increase in
    resolution. I'm confident that a 450D image downsampled to
    6MP would be significantly better than a 300D image.
    Put it this way. The 12MP P&S digital cameras (eg SX200IS)
    have a pixel density of 43MP/cm^2. the 22.3x14.9mm sensor
    used in the cropped canon cameras has an area of 3.3227cm^2,
    so for the same pixel density an SLR could have a 142MP
    sensor. ie, a 142MP 1.6x crop DSLR would deliver similar
    noise levels to a 12MP P&S.
    The current 10-15MP cameras are obviously a long long way
    short of the pixel densities in P&S cameras, and despite
    concern that the higher pixel counts are increasing noise,
    they are still significantly better than P&S.
    Doug Jewell, Apr 23, 2009
  8. Eugene

    Derge Guest

    A sensor is a silicon chip. Its surface is divided into an array of
    photosites. Each photosite contributes to the number of pixels.
    What I said was that the *image* made *from* the smaller pixels would
    be less noisy.

    The EOS 1000D captures images at 3888x2592.

    The EOS 300D captures images at 3072x2048.

    If you resize an EOS 1000D image to 3072x2048, it will be less noisy
    than the *same* image from an EOS 300D.

    When you resize the image, the same principles that make the smaller
    pixels noisier are working in reverse.

    The fact is that the more samples you take, the less accurate any of
    them need to be. This is why there is no "sweet spot" for APS-C
    sensors. The only reason we don't have 400 megapixels DSLRs is because
    our cameras and our personal computers aren't powerful enough yet. If
    they were, we would.
    Derge, Apr 23, 2009
  9. Eugene

    Don Stauffer Guest

    The DSLR has a number of advantages over other types of cameras. I have
    never considered pixel size one of them. One can use ANY focal plane in
    a DSLR, in a compact, a rangefinder, or any other type of camera.

    To me the big advantages of an SLR are easily interchangable lenses, and
    the ability to see the actual optical focus when using manual focus.
    Also, for macro work there is no parallax error.

    I do not consider electronic viewfinders acceptable until the display
    has as many pixels as the primary sensor.
    Don Stauffer, Apr 23, 2009

  10. That may be quite some time, or quite a large camera back.
    What's the maximum number of ppi can an LCD properly display? Most
    monitors are less than 100 ppi.
    What can the human eye resolve- and when does extra resolution become
    John McWilliams, Apr 23, 2009
  11. For me it's not the resolution thats the problem, it the time lag from
    when I change something to when it changes on the LCD. Until LCD become
    as fast as an optical viewfinder it's a no sale for me.
    As it stands now, sports photography with electronic viewfinders would
    be impossible.

    John Passaneau
    John Passaneau, Apr 23, 2009
  12. Eugene

    me Guest

    You don't understand. It's just a different sport!
    me, Apr 23, 2009
  13. Why do you want it be so much better than an optical viewfinder, and
    so much better than you can see?
    Chris Malcolm, Apr 24, 2009
  14. Eugene

    Don Stauffer Guest

    I don't think I do. The optical viewfinder should be pretty close to
    res of focal plane. I can see the most minute changes in the lens focus
    on my D40. I can see MUCH more detail than I can on any LCD screen I
    have used on other cameras, like my P & S.

    I have not run the numbers on visual acuity, but I certainly can tell I
    can see FAR better in my SLRs than I can on an LCD screen.
    Don Stauffer, Apr 24, 2009
  15. Eugene

    Don Stauffer Guest

    True. Probably half or even a quarter would do.

    Some SLRs have optical focusing aids- microprisms and such. These
    increase the accuracy of focus and rely on optical "tricks." I doubt if
    an LCD viewfinder would be able to use such techniques.
    Don Stauffer, Apr 25, 2009
  16. Eugene

    J. Clarke Guest

    No, but it can magnify the image.
    J. Clarke, Apr 25, 2009
  17. Eugene

    Bob Larter Guest

    It's enough of a pain to magnify an image you've just taken, the last
    thing in the world that I want is to have to do it while focusing.
    Bob Larter, Apr 25, 2009
  18. That's just an interface issue. Some cameras have the option of
    instantly magnifying the image as soon as you move the manual focus
    Chris Malcolm, Apr 25, 2009
  19. Eugene

    J. Clarke Guest

    Yep, the problem with the ones I've seen is that they don't let you specify
    what portion of the image is to be magnified, they just magnify the center.
    Seems to me that done right it could be more convenient under some
    circumstances than using an eyepiece magnifier.
    J. Clarke, Apr 25, 2009
  20. Eugene

    Doug Jewell Guest

    My Canon 450D allows you to move the focus zone around the
    image. This is the area that it will use for contrast-detect
    auto-focus, or that it will enlarge for manual focus. You
    can use a corner of the image for focus if you really want
    to. It works ok, but personally I prefer the optical viewfinder.
    Doug Jewell, Apr 26, 2009
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