D100 and Rebel WTF??? 6MP vs 3MP Opinions please....

Discussion in 'Digital Photography' started by The Dude, Jan 6, 2004.

  1. The Dude

    The Dude Guest

    I've shot over 10,000 shots on my D100 since I got it in Aug '02. I just
    bought my wife a Canon 300D (she's always loved her film rebel). I have
    always shot at large/fine (that's 6MP, low compression jpgs). Having looked
    at the review of the Foveon based SD9 at dpreview, I wanted to test
    something. If you look at p.20 of the review, you can see that Phil shows
    us that the ressed-up 3MP images of the SD9 carry at least as much detail as
    the native 6 MP inages of the D60. Now, I know that Foveon has other issues
    (noise, moire, contrast, raw only etc) and I'm not trying to start a Foveon
    vs Bayer flame war here. Rather, it made me curious about shooting with the
    D100 and 300D in 3MP mode. Would those 3MP images, ressed-up, carry the
    detail of the native 6MP I've been shooting? Well, damn it if the answer
    isn't YES!

    I started with some of my sharpest 6MP pictures. Well exposed, from a
    tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a Photoshop
    resize of the 3000x2000 image to 2240x1498. I then saved it as small.jpg.
    I reopened it, ressed it up, and compared it, per pixel, to the original 6MP
    image. I was startled by what I saw. No discernable change in image
    quality?!?! I proceeded by shooting at medium/fine and large/fine. Again,
    no meaningful difference once the medium file was ressed up. I repeated the
    exact same observations with the Canon 300D. Please repeat these tests
    yourselves and let mw know your opinions. This revelation will save lots of
    HD space and permit far more images on CF.
     
    The Dude, Jan 6, 2004
    #1
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  2. The Dude

    Michael Guest

    Hi,

    > I started with some of my sharpest 6MP pictures. Well exposed, from a
    > tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a

    Photoshop
    > resize of the 3000x2000 image to 2240x1498. I then saved it as small.jpg.
    > I reopened it, ressed it up, and compared it, per pixel, to the original

    6MP
    > image. I was startled by what I saw. No discernable change in image
    > quality?!?!


    If you downsize an image by 25%, save it in a lossy format like jpg, then
    load it and size it back up, you will have a signifficant loss of
    information compared to the original image. My guess is something like 50%
    loss, depending on the jpeg quality setting (in your example 44% of all
    pixels are gone, plus another 5-10% in the jpeg compression).

    Photoshop does not resize simply by eliminating 1 out of every 4 pixels. It
    applies a special algorithm to reduce aliasing and preserve the original
    "look" of the image, even when it has less pixels to do it with. It does the
    same thing when it sizes back up from 3 to 4 pixels. It is not unlikely that
    it can do this so well that your eye is fooled into thinking there is no
    difference. But there is - at least 44% of the image is now synthetically
    generated by a computer program, whereas the original image was captured
    through the lens.

    Try to create a new image in Photoshop - 5x3 pixels in size. Draw a tiny
    pyramid, 5 pix at the bottom, 3 in the middle and 1 on top. Then ask
    Photoshop to scale it up to 640 x 400. You won't simply get 9 huge blocks
    stacked on top of eachother, you'll get something that "looks" more like the
    small image. Photoshop is adding what it thinks is missing to draw a big
    pyramid, based on the information it can extract from the small image. It
    doesn't look very nice but you get the idea.

    > yourselves and let mw know your opinions. This revelation will save lots

    of
    > HD space and permit far more images on CF.


    The fact that scaling a 3 mpix image up to 6 mpix in Paintshop or Photoshop
    makes the image look almost as good as a 6 mpix image is hardly a
    revelation. It's more like a testament of the effectiveness of the
    algorithms these programs apply to help people like me who are short on real
    megapixels .. :)

    /Michael
     
    Michael, Jan 6, 2004
    #2
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  3. The Dude

    Tom Thackrey Guest

    On 6-Jan-2004, "The Dude" <.> wrote:

    > I've shot over 10,000 shots on my D100 since I got it in Aug '02. I just
    > bought my wife a Canon 300D (she's always loved her film rebel). I have
    > always shot at large/fine (that's 6MP, low compression jpgs). Having
    > looked
    > at the review of the Foveon based SD9 at dpreview, I wanted to test
    > something. If you look at p.20 of the review, you can see that Phil shows
    > us that the ressed-up 3MP images of the SD9 carry at least as much detail
    > as
    > the native 6 MP inages of the D60. Now, I know that Foveon has other
    > issues
    > (noise, moire, contrast, raw only etc) and I'm not trying to start a
    > Foveon
    > vs Bayer flame war here. Rather, it made me curious about shooting with
    > the
    > D100 and 300D in 3MP mode. Would those 3MP images, ressed-up, carry the
    > detail of the native 6MP I've been shooting? Well, damn it if the answer
    > isn't YES!
    >
    > I started with some of my sharpest 6MP pictures. Well exposed, from a
    > tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a
    > Photoshop
    > resize of the 3000x2000 image to 2240x1498. I then saved it as small.jpg.
    > I reopened it, ressed it up, and compared it, per pixel, to the original
    > 6MP
    > image. I was startled by what I saw. No discernable change in image
    > quality?!?! I proceeded by shooting at medium/fine and large/fine.
    > Again,
    > no meaningful difference once the medium file was ressed up. I repeated
    > the
    > exact same observations with the Canon 300D. Please repeat these tests
    > yourselves and let mw know your opinions. This revelation will save lots
    > of
    > HD space and permit far more images on CF.


    Please examine the logic of this. Taken to its extreme you could start with
    a 1 pixel image and resize it to 6MP with no change in image quality. Except
    for trivial cases, it can't happen. This is the perpetual motion machine of
    digital imaging.

    Try this. Take a news paper and tack it to a wall. With the camera on a
    tripod, move or zoom back until you can't read the newspaper in the taken
    image at max resolution. Now move in just enough so you can read it. Change
    the settings to capture a lower resolution image and resize it to the high
    res dimensions. Can you still read the newspaper?

    There is still no free lunch.

    --
    Tom Thackrey
    www.creative-light.com
    tom (at) creative (dash) light (dot) com
    do NOT send email to (it's reserved for spammers)
     
    Tom Thackrey, Jan 6, 2004
    #3
  4. I will always shoot in the finest jpg mode or raw. One might want to crop
    later. Best to start with as much detail as possible. Also, printing your
    shots 8x10 or larger might change your mind.
     
    Charles Schuler, Jan 6, 2004
    #4
  5. The Dude

    The Dude Guest

    "Tom Thackrey" <> wrote in message
    news:9iFKb.7372$...
    >
    > On 6-Jan-2004, "The Dude" <.> wrote:
    >
    > > I've shot over 10,000 shots on my D100 since I got it in Aug '02. I

    just
    > > bought my wife a Canon 300D (she's always loved her film rebel). I have
    > > always shot at large/fine (that's 6MP, low compression jpgs). Having
    > > looked
    > > at the review of the Foveon based SD9 at dpreview, I wanted to test
    > > something. If you look at p.20 of the review, you can see that Phil

    shows
    > > us that the ressed-up 3MP images of the SD9 carry at least as much

    detail
    > > as
    > > the native 6 MP inages of the D60. Now, I know that Foveon has other
    > > issues
    > > (noise, moire, contrast, raw only etc) and I'm not trying to start a
    > > Foveon
    > > vs Bayer flame war here. Rather, it made me curious about shooting with
    > > the
    > > D100 and 300D in 3MP mode. Would those 3MP images, ressed-up, carry the
    > > detail of the native 6MP I've been shooting? Well, damn it if the

    answer
    > > isn't YES!
    > >
    > > I started with some of my sharpest 6MP pictures. Well exposed, from a
    > > tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a
    > > Photoshop
    > > resize of the 3000x2000 image to 2240x1498. I then saved it as

    small.jpg.
    > > I reopened it, ressed it up, and compared it, per pixel, to the original
    > > 6MP
    > > image. I was startled by what I saw. No discernable change in image
    > > quality?!?! I proceeded by shooting at medium/fine and large/fine.
    > > Again,
    > > no meaningful difference once the medium file was ressed up. I repeated
    > > the
    > > exact same observations with the Canon 300D. Please repeat these tests
    > > yourselves and let mw know your opinions. This revelation will save

    lots
    > > of
    > > HD space and permit far more images on CF.

    >
    > Please examine the logic of this. Taken to its extreme you could start

    with
    > a 1 pixel image and resize it to 6MP with no change in image quality.

    Except
    > for trivial cases, it can't happen. This is the perpetual motion machine

    of
    > digital imaging.


    How silly. Of course I understand that most simple concept. Let me be more
    clear in my assertion. The logic of this is as follows... the Bayer
    interpolation yields a precise 3MP image for a 6MP sensor. It seems that
    little is gained in actual resolution in the jump from 3 to 6. Those
    missing "actual" pixels that adobe guesses, are as good as the Beyer
    interpolation. Bayer requires it's own guess work. It looks like Bayer
    interpolation yields all it's detail in half of the actual CCD or CMOS pixel
    count. I have 2 cameras I have proved this with. Please give it a try
    before writing it off. Take a picture of that newspaper at 3MP and 6MP.
    You will see a nearly perfect match.
     
    The Dude, Jan 6, 2004
    #5
  6. The Dude

    The Dude Guest

    "Charles Schuler" <> wrote in message
    news:...
    > I will always shoot in the finest jpg mode or raw. One might want to crop
    > later. Best to start with as much detail as possible. Also, printing

    your
    > shots 8x10 or larger might change your mind.


    I frequently print at 13x19'. Believe me, I understand. That is why, up
    til' now, I always shot at large/fine on my D100. However, if all of the
    detail of the 6MP image can truly be resolved in the 3MP, it makes no sense
    to use the large setting. My theory is that a 6mp Bayer mosaic pattern
    yields 3MP of true detail. Likewise, a 4MP sensor would yield 2MP of true
    detail. And so on. Again, see here...

    http://www.dpreview.com/reviews/sigmasd9/page20.asp

    The ressed-up 3MP images on the left provide at least as much detail
    information as the native 6MP images on the right. My tests with the D100
    at medium vs. large show no significant difference in detail. Try this to
    prove it to yourself. Take the exact same image at large and medium.
    Increase the size of the medium to match the large and decide how much the
    "guesswork" of Adobe is inferior to the guesswork of the native 6MP Bayer
    image. Very little change. For fun, size'em both up to 12MP. Is there any
    difference in the images. Try it!!
     
    The Dude, Jan 6, 2004
    #6
  7. The Dude

    Tom Thackrey Guest

    On 6-Jan-2004, "The Dude" <.> wrote:

    > "Tom Thackrey" <> wrote in message
    > news:9iFKb.7372$...
    > >
    > > On 6-Jan-2004, "The Dude" <.> wrote:
    > >
    > > > I've shot over 10,000 shots on my D100 since I got it in Aug '02. I

    > just
    > > > bought my wife a Canon 300D (she's always loved her film rebel). I
    > > > have
    > > > always shot at large/fine (that's 6MP, low compression jpgs). Having
    > > > looked
    > > > at the review of the Foveon based SD9 at dpreview, I wanted to test
    > > > something. If you look at p.20 of the review, you can see that Phil

    > shows
    > > > us that the ressed-up 3MP images of the SD9 carry at least as much

    > detail
    > > > as
    > > > the native 6 MP inages of the D60. Now, I know that Foveon has other
    > > > issues
    > > > (noise, moire, contrast, raw only etc) and I'm not trying to start a
    > > > Foveon
    > > > vs Bayer flame war here. Rather, it made me curious about shooting
    > > > with
    > > > the
    > > > D100 and 300D in 3MP mode. Would those 3MP images, ressed-up, carry
    > > > the
    > > > detail of the native 6MP I've been shooting? Well, damn it if the

    > answer
    > > > isn't YES!
    > > >
    > > > I started with some of my sharpest 6MP pictures. Well exposed, from a
    > > > tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a
    > > > Photoshop
    > > > resize of the 3000x2000 image to 2240x1498. I then saved it as

    > small.jpg.
    > > > I reopened it, ressed it up, and compared it, per pixel, to the
    > > > original
    > > > 6MP
    > > > image. I was startled by what I saw. No discernable change in image
    > > > quality?!?! I proceeded by shooting at medium/fine and large/fine.
    > > > Again,
    > > > no meaningful difference once the medium file was ressed up. I
    > > > repeated
    > > > the
    > > > exact same observations with the Canon 300D. Please repeat these
    > > > tests
    > > > yourselves and let mw know your opinions. This revelation will save

    > lots
    > > > of
    > > > HD space and permit far more images on CF.

    > >
    > > Please examine the logic of this. Taken to its extreme you could start

    > with
    > > a 1 pixel image and resize it to 6MP with no change in image quality.

    > Except
    > > for trivial cases, it can't happen. This is the perpetual motion machine

    > of
    > > digital imaging.

    >
    > How silly. Of course I understand that most simple concept. Let me be
    > more
    > clear in my assertion. The logic of this is as follows... the Bayer
    > interpolation yields a precise 3MP image for a 6MP sensor. It seems that
    > little is gained in actual resolution in the jump from 3 to 6. Those
    > missing "actual" pixels that adobe guesses, are as good as the Beyer
    > interpolation. Bayer requires it's own guess work. It looks like Bayer
    > interpolation yields all it's detail in half of the actual CCD or CMOS
    > pixel
    > count. I have 2 cameras I have proved this with. Please give it a try
    > before writing it off. Take a picture of that newspaper at 3MP and 6MP.
    > You will see a nearly perfect match.


    I have to admit, they're much closer than I would have expected. My
    apologies. I resized the smaller image and compared them with photoshop's
    difference and the difference was virtually nill. Sad, in a way.

    --
    Tom Thackrey
    www.creative-light.com
    tom (at) creative (dash) light (dot) com
    do NOT send email to (it's reserved for spammers)
     
    Tom Thackrey, Jan 6, 2004
    #7
  8. The Dude

    Jon Noble Guest

    I too have always assumed the more pixels the better. And it is true.
    However, I have a story similar to yours. Relatives of mine recently came
    back from Africa with a full CD of pictures, shot with several cameras. One
    image caught my fancy even though it was 1.3 mp. I used Fred Miranda's SI
    plugin for Photoshop to resize this picture so it could be printed 13x19 at
    240 ppi using my Canon i9100. The results were stunning, far better than I
    ever expected.

    Everyone says you can't print pictures from a 1.3 megapixel camera at 13x19,
    but upping the rez with intelligent algorithms makes it worthwhile.

    OK, not exactly your situation, but another example of how good up rezzing
    can be.

    -Jon

    "The Dude" <.> wrote in message
    news:3ffb2d18$0$96249$...
    >
    > "Charles Schuler" <> wrote in message
    > news:...
    > > I will always shoot in the finest jpg mode or raw. One might want to

    crop
    > > later. Best to start with as much detail as possible. Also, printing

    > your
    > > shots 8x10 or larger might change your mind.

    >
    > I frequently print at 13x19'. Believe me, I understand. That is why, up
    > til' now, I always shot at large/fine on my D100. However, if all of the
    > detail of the 6MP image can truly be resolved in the 3MP, it makes no

    sense
    > to use the large setting. My theory is that a 6mp Bayer mosaic pattern
    > yields 3MP of true detail.
     
    Jon Noble, Jan 6, 2004
    #8
  9. The Dude

    Paul Rubin Guest

    "Jon Noble" <> writes:
    > I too have always assumed the more pixels the better. And it is true.


    Really not though. Compare a 5MP consumer digicam with a 1/2" sensor
    to a ~3 MP Nikon D1 or Canon D30. Size of the pixels on the sensors
    sometimes matters more than pixel count.
     
    Paul Rubin, Jan 6, 2004
    #9
  10. The Dude

    Chris Brown Guest

    In article <3ffb0a8d$0$7065$>, The Dude <.> wrote:
    >
    >I started with some of my sharpest 6MP pictures. Well exposed, from a
    >tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a Photoshop
    >resize of the 3000x2000 image to 2240x1498. I then saved it as small.jpg.
    >I reopened it, ressed it up, and compared it, per pixel, to the original 6MP
    >image. I was startled by what I saw. No discernable change in image
    >quality?!?! I proceeded by shooting at medium/fine and large/fine. Again,
    >no meaningful difference once the medium file was ressed up. I repeated the
    >exact same observations with the Canon 300D. Please repeat these tests
    >yourselves and let mw know your opinions. This revelation will save lots of
    >HD space and permit far more images on CF.


    Doubt it - you may want to consider using RAW mode, and/or applying some
    unsharp mask to your images.

    I just did this test with my 10D. Here's the result:

    http://www.narcissus.uklinux.net/6vs3.jpg

    The picture was converted from raw with no sharpening applied, duplicated.
    One of the copies was resized to 3 megapixels (2160*1440), and then back to
    6 megapixels (3072*2048) using bicubic interpolation. Each image then had
    the same level of (relatively aggressive) unsharp mask applied. Both samples
    are fragments viewed at actual-pixel size. The shot was handheld at 100 ISO,
    using a Canon EF 50mm f/1.4 lens and a 420EX flash. I find the difference in
    image quality quite discernable indeed!

    I think it should be pretty obvious which is which...
     
    Chris Brown, Jan 7, 2004
    #10
  11. The Dude

    VT Guest

    On Tue, 06 Jan 2004 22:56:43 GMT, "Tom Thackrey"
    <> wrote:

    >
    >On 6-Jan-2004, "The Dude" <.> wrote:
    >
    >> I have 2 cameras I have proved this with. Please give it a try
    >> before writing it off. Take a picture of that newspaper at 3MP and 6MP.
    >> You will see a nearly perfect match.

    >
    >I have to admit, they're much closer than I would have expected. My
    >apologies. I resized the smaller image and compared them with photoshop's
    >difference and the difference was virtually nill. Sad, in a way.


    Thanks very much to both of you for your extremely interesting dialog.

    Downsizing from 6Mp image to 3Mp then re-UPsizing appears not to have
    too many losses from your conversation.

    It would also seem taking the original image at 3Mp on a 6Mp digicam
    would also retain all the details of the image as if shot at the full
    6Mp (since I assume the camera would do the downsize from its 6Mp
    mosaic image to store the 3Mp image).

    However a digicam with only 3Mp bayer sensor could not be rez'd up to
    to get the 6Mp quality - since would only really then have 1/2 of the
    CCD element count info (ie: 1.5Mp's "worth" )

    This kind of makes sense since my understanding is the Nyquist limit
    on (linear) resolution seems to be about root(2) of the actual pixel
    count in each linear dimension for a Bayer mosaic sensor -
    whereas the Foven sensor shows that closer to a 1 pixel-row to 1 line
    resolution limit is possible for non-mosaic images.

    Thanks to both The Dude and Tom Thackrey for this very interesting
    dialog.

    --
    Vincent
    remove CLOTHES for e-mail

    http://UnknownVincent.cjb.net/
     
    VT, Jan 7, 2004
    #11
  12. The Dude

    Guest

    In message <3ffb0a8d$0$7065$>,
    "The Dude" <.> wrote:

    >I've shot over 10,000 shots on my D100 since I got it in Aug '02. I just
    >bought my wife a Canon 300D (she's always loved her film rebel). I have
    >always shot at large/fine (that's 6MP, low compression jpgs). Having looked
    >at the review of the Foveon based SD9 at dpreview, I wanted to test
    >something. If you look at p.20 of the review, you can see that Phil shows
    >us that the ressed-up 3MP images of the SD9 carry at least as much detail as
    >the native 6 MP inages of the D60. Now, I know that Foveon has other issues
    >(noise, moire, contrast, raw only etc) and I'm not trying to start a Foveon
    >vs Bayer flame war here. Rather, it made me curious about shooting with the
    >D100 and 300D in 3MP mode. Would those 3MP images, ressed-up, carry the
    >detail of the native 6MP I've been shooting? Well, damn it if the answer
    >isn't YES!
    >
    >I started with some of my sharpest 6MP pictures. Well exposed, from a
    >tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a Photoshop
    >resize of the 3000x2000 image to 2240x1498. I then saved it as small.jpg.
    >I reopened it, ressed it up, and compared it, per pixel, to the original 6MP
    >image. I was startled by what I saw. No discernable change in image
    >quality?!?! I proceeded by shooting at medium/fine and large/fine. Again,
    >no meaningful difference once the medium file was ressed up. I repeated the
    >exact same observations with the Canon 300D. Please repeat these tests
    >yourselves and let mw know your opinions. This revelation will save lots of
    >HD space and permit far more images on CF.


    You're missing the forest for the trees; an image is not a fixed pixel
    spacing; it is a collection of pixels, which vary in number. You can
    not assess the detail of an image by looking at it pixel-for-pixel or at
    any PPI resolution, unless you are comparing two images of the same
    size.

    A camera that is properly filtering the light striking the sensor can
    *NEVER* have a black pixel next to a white pixel. It is impossible, and
    any system that can sample that way at its native resolution is
    cheating, and allowing garbage to get recorded. It *is* possible if you
    leave out the filtering, or if a quick'n'dirty downsizing algorithm is
    used on the data. "Nearest Neighbor" is the quickest and dirtiest, and
    6.3MP bayer images downsized to 3.43MP with this algorithm look
    strikingly similar to SD9 images, but 1Ds images with the same target
    size look even closer. I suspect that what the SD9 is giving you is
    what you would get if you used a properly-filtered 23MP image, and used
    nearest neighbor to downsize it to 3.43MP.

    Unless you were using the very sharpest of lenses (like expensive
    telephoto primes), a 23MP APS-size image would probably look pretty
    bland "pixel for pixel", compared to the garbage you would get with the
    3.43MP Nearest Neighbor downsize, but actually contains up to 6.7x times
    as much detail (depending, of course, on the optics).

    Printing both at the same size, the one that looked better "pixel for
    pixel" will look like utter crap next to the "pixel for pixel blurry".

    And, of course, if the lens is sharp enough, the properly-filtered image
    still contains detail at legal frequencies it has attenuated that can be
    boosted with USM at sub-pixel radii; the sharper the lens, and the less
    noise you have, the better you can restore them.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Jan 7, 2004
    #12
  13. The Dude

    Guest

    In message <3ffb178e$0$95111$>,
    "Michael" <> wrote:

    >Try to create a new image in Photoshop - 5x3 pixels in size. Draw a tiny
    >pyramid, 5 pix at the bottom, 3 in the middle and 1 on top. Then ask
    >Photoshop to scale it up to 640 x 400. You won't simply get 9 huge blocks
    >stacked on top of eachother, you'll get something that "looks" more like the
    >small image. Photoshop is adding what it thinks is missing to draw a big
    >pyramid, based on the information it can extract from the small image. It
    >doesn't look very nice but you get the idea.


    It depends which algorithm you choose, but none of them do what you
    suggest. Photoshop's "image size" does not know or care that your
    pyramid has 3 edges. It sees 15 pixels, and nothing more.

    If you want a real pyramid, use the vector tools.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Jan 7, 2004
    #13
  14. The Dude

    Lew Guest

    What you have discovered is that a factor of 1.4 in resolution makes only a
    small difference in image quality in real world pictures. Even a factor of
    2.0 makes only a small noticeable difference since most objects that are
    seen in photos involve much more than one pixel in two directions. A
    difference should be seen if a picture is made of something like a picket
    fence at an angle that dissapears in the distance. The higher resolution
    photo should show separate pickets at a greater distance. If those pickets
    are colored and the camera is a Bayer type, the color will be lost and
    pickets will become grey at a distance. If a Foveon type, the color should
    remain correct, but the number of pickets should be the same as a Bayer with
    one-third the pixel count.

    The loss of color information for small items is of little consequence; your
    eye does not recognise color for very small objects. Color TV makes good use
    of this. The color resolution in a TV picture is less than one tenth the
    resolution of the picture detail and is not a problem with real world TV
    pictures.

    Printing a picture at 140 pixels per inch is only a little worse than at 200
    per inch, especially if jaggies are reduced by interpolating up in
    resolution. Very good lookng, large prints can be made for most pictures of
    real world objects with even less than 100 pixels per inch in resolution if
    interpolated and sharpened correctly. However, the picket fence picture
    would show more pickets with a high resolution image. Some stray hairs on a
    model might show with the higher resolution. However, if you did not have
    the high resolution image for comparison, you would be happy with a lower
    resolution image that did not show the stray hairs.

    Jpeg compression has been condemned by at least one earlier poster. Jpeg
    makes use of compression that minimizes loss of visible information. As with
    color TV, image data that is not required for a visual image is discarded
    for modest file size reduction. When greater file size reduction is
    required, barely visible information is lost. Repeated saving with high
    quality jpeg compression has been demonstrated to not reduce visible image
    quality and retains the advantage of reduced file size compared to
    uncompressed. Repeated saving with low quality jpeg rapidly reduces quality
    without the file size getting smaller with each save. You can verify this
    yourself by repeatedly opening and saving a photo file. Start with a tiff,
    and save as a high quality jpeg. Visually compare the tiff with the jpeg.
    Open and resave the jpeg several times and compare again. Most people see no
    difference if the jpeg quality selected is high or maximum. Everyone sees
    the difference when low quality is selected.

    Lew

    "The Dude" <.> wrote in message
    news:3ffb0a8d$0$7065$...
    > I've shot over 10,000 shots on my D100 since I got it in Aug '02. I just
    > bought my wife a Canon 300D (she's always loved her film rebel). I have
    > always shot at large/fine (that's 6MP, low compression jpgs). Having

    looked
    > at the review of the Foveon based SD9 at dpreview, I wanted to test
    > something. If you look at p.20 of the review, you can see that Phil shows
    > us that the ressed-up 3MP images of the SD9 carry at least as much detail

    as
    > the native 6 MP inages of the D60. Now, I know that Foveon has other

    issues
    > (noise, moire, contrast, raw only etc) and I'm not trying to start a

    Foveon
    > vs Bayer flame war here. Rather, it made me curious about shooting with

    the
    > D100 and 300D in 3MP mode. Would those 3MP images, ressed-up, carry the
    > detail of the native 6MP I've been shooting? Well, damn it if the answer
    > isn't YES!
    >
    > I started with some of my sharpest 6MP pictures. Well exposed, from a
    > tripod, shot through 28-70mm 2.8 AF-S... an awesome lens. I did a

    Photoshop
    > resize of the 3000x2000 image to 2240x1498. I then saved it as small.jpg.
    > I reopened it, ressed it up, and compared it, per pixel, to the original

    6MP
    > image. I was startled by what I saw. No discernable change in image
    > quality?!?! I proceeded by shooting at medium/fine and large/fine.

    Again,
    > no meaningful difference once the medium file was ressed up. I repeated

    the
    > exact same observations with the Canon 300D. Please repeat these tests
    > yourselves and let mw know your opinions. This revelation will save lots

    of
    > HD space and permit far more images on CF.
    >
    >
     
    Lew, Jan 7, 2004
    #14
  15. The Dude

    Guest

    In message <3ffb2612$0$87180$>,
    "The Dude" <.> wrote:

    >How silly. Of course I understand that most simple concept. Let me be more
    >clear in my assertion. The logic of this is as follows... the Bayer
    >interpolation yields a precise 3MP image for a 6MP sensor. It seems that
    >little is gained in actual resolution in the jump from 3 to 6.


    That depends on the quality of focus.

    >Those
    >missing "actual" pixels that adobe guesses, are as good as the Beyer
    >interpolation.


    There is no "bayer interpolation" of pixels. The only interpolation is
    the full RGB set for the pixel.

    >Bayer requires it's own guess work.


    Bayer does not "guess" anything. It "assumes" that chromatic values are
    not going to change at more than half the pixel rate. The luminance
    values are extremely accurate, if done correctly, and they are what
    count the most. We don't see RGB color with our eyes and brains; we see
    luminance with a ghost of color hovering around it, mainly fabricated by
    the brain.

    >It looks like Bayer
    >interpolation yields all it's detail in half of the actual CCD or CMOS pixel
    >count. I have 2 cameras I have proved this with. Please give it a try
    >before writing it off. Take a picture of that newspaper at 3MP and 6MP.
    >You will see a nearly perfect match.


    You are confusing a lot of issues. "Bayer" has nothing to do with any
    of this. It is just a coincidence that the only Foveon cameras
    available have no anti-aliasing filter (and the SD9 doesn't even have
    microlenses). All sensors should have some degree of anti-aliasing
    filter; at least with current sensor technology that is unable to
    out-sample the sharpest lenses used. Any number of reasons could make a
    3MP downsize seem to contain everything the 6MP contains. Motion blur
    of the camera often occurs in circles; preventing any real focus over
    the length of the exposure; zoom lenses are often soft at their max zoom
    and/or wide open. The AA filter suppresses detail that can be
    resurrected (if present) with a USM of about 0.3 to 0.5 pixel radius at
    200 to 500%, and this detail is hard to see without the USM.

    If you use a sharp lens, with a flash, focused precisely on the subject,
    you *will* lose detail downsizing to 70.7%. It's really a matter of
    degree, and it has as much to do with the lens and camera handling as it
    does with anything else.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Jan 7, 2004
    #15
  16. The Dude

    Guest

    In message <L2HKb.7424$>,
    "Tom Thackrey" <> wrote:

    >I have to admit, they're much closer than I would have expected. My
    >apologies. I resized the smaller image and compared them with photoshop's
    >difference and the difference was virtually nill. Sad, in a way.


    Well, you know, halving the pixels only reduces the height and width by
    29.3%, which really is not as much as "50%" sounds like. It's not
    really that big of a difference.

    The higher we go in megapixels, the less any image is going to suffer
    tremendously from a 70.7% resize. The benefit of increased pixel count
    is not linear; it's not even linear to a single dimension (square root
    of pixel count).
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Jan 7, 2004
    #16
  17. "The Dude" <.> writes:

    >Again,
    >no meaningful difference once the medium file was ressed up. I repeated the
    >exact same observations with the Canon 300D. Please repeat these tests
    >yourselves and let mw know your opinions. This revelation will save lots of
    >HD space and permit far more images on CF.


    When you reduce the size from 6 to 3 MP, the maximum possible linear
    resolution is reduced to 70% of what it was. Now, the full-size image
    may not have actual detail up to that limit, because the anti-aliasing
    filter necessarily removes some fine detail below the theoretical limit.
    When you downsize to 3 MP, you're using a digital filter that can be a
    bit better about keeping information than the physical AA filter. Thus,
    the 6 MP image may not lose as much as you'd expect, because it's
    somewhat weak on that high-frequency detail in the first place.

    However, there is *some* loss, if the original is sharp. For example:
    go to http://www.dpreview.com/reviews/canoneos300d/page21.asp and
    download the upper left full-size test chart. Look at the resolution
    test section just to the right of centre, a sort of sloping wedge.
    There's another wedge above that too, for testing horizontal resolution.
    Look and see how far along the wedges you can go and still see 9 clearly
    resolved black bars. You'll have to view the image at 100% scale at
    least to make any judgements. I'd say the limit on this particular test
    is somewhere between 14 and 15, which means 1400-1500 lines per picture
    height. (Note that this isn't the resolution limit, just a point up to
    which I know I can get clean images without artifacts).

    Now take this image and reduce it from 3072 to about 2172 pixels wide.
    Look at the resolution wedges again. Now the highest resolution clean
    pattern is at about 10 or 11. Resizing the image back up to 3072 wide
    does not improve that figure at all. In other words, detail that was in
    the original image has been permanently lost, at least in this example.

    Whether there is any such fine detail in your images depends on
    technique (use of tripod, shutter speed, focusing, depth of field).
    Whether you can *see* any loss of detail even if some happens depends on
    the subject of the photo. Maybe for what you shoot and the way you
    shoot, there won't be any noticeable loss. But it isn't *always*
    visually lossless.

    The other question which you haven't tested: is there any difference in
    quality between just setting the camera to 3 MP output, and shooting at
    6 MP but reducing later to 3 MP using Photoshop or Irfanview? The
    former is attractive because you can store more images on a given size
    card, but the latter gives you more control of the resizing process.

    Dave
     
    Dave Martindale, Jan 7, 2004
    #17
  18. "The Dude" <.> writes:

    >The ressed-up 3MP images on the left provide at least as much detail
    >information as the native 6MP images on the right.


    But not all of the "detail information" in the 3 MP images is actually
    real. There are a number of places where what you see in the images is
    very unlikely to be what was actually present in the original scene.
    This is a known problem with any image capture device which lacks
    adequate anti-alias filtering. The Sigma cameras record *something*
    that looks sharp when presented with too-fine detail, even if it's
    sometimes wrong. The Bayer cameras show you a blur when they can't
    resolve fine detail, which is at least theoretically the more correct
    behaviour.

    It's like the difference between starting with a 12 MP image and
    resizing down to 3 MP using "nearest neighbor" or "bicubic"
    resampling. The first looks sharp, but has problems. The second
    looks less sharp but more faithfully records the original scene.

    If the Sigma camera had used an anti-aliasing filter, like the
    Canon/Bayer camera did, the true difference in resolution would be more
    apparent. In addition, the Sigma raw converter software applies more
    sharpening in software than the Canon in-camera software, so the Sigma
    images look sharper when the fine detail content is actually the same.

    Anyway, don't conclude that 3MP = 6MP based on *this* comparison.

    Dave
     
    Dave Martindale, Jan 7, 2004
    #18
  19. The Dude

    The Dude Guest

    "Lew" <> wrote in message
    news:R%KKb.4143$...
    > What you have discovered is that a factor of 1.4 in resolution makes only

    a
    > small difference in image quality in real world pictures. Even a factor of
    > 2.0 makes only a small noticeable difference since most objects that are
    > seen in photos involve much more than one pixel in two directions. A
    > difference should be seen if a picture is made of something like a picket
    > fence at an angle that dissapears in the distance. The higher resolution
    > photo should show separate pickets at a greater distance. If those pickets
    > are colored and the camera is a Bayer type, the color will be lost and
    > pickets will become grey at a distance. If a Foveon type, the color should
    > remain correct, but the number of pickets should be the same as a Bayer

    with
    > one-third the pixel count.


    You would think. But look at the 7th picture down on this page...
    http://www.dpreview.com/reviews/sigmasd9/page20.asp

    The vertical details are actually better resolved on the ressed-up 3MP
    image.


    > The loss of color information for small items is of little consequence;

    your
    > eye does not recognise color for very small objects. Color TV makes good

    use
    > of this. The color resolution in a TV picture is less than one tenth the
    > resolution of the picture detail and is not a problem with real world TV
    > pictures.
    >
    > Printing a picture at 140 pixels per inch is only a little worse than at

    200
    > per inch, especially if jaggies are reduced by interpolating up in
    > resolution. Very good lookng, large prints can be made for most pictures

    of
    > real world objects with even less than 100 pixels per inch in resolution

    if
    > interpolated and sharpened correctly. However, the picket fence picture
    > would show more pickets with a high resolution image. Some stray hairs on

    a
    > model might show with the higher resolution. However, if you did not have
    > the high resolution image for comparison, you would be happy with a lower
    > resolution image that did not show the stray hairs.


    But doesn't this ignore the guesswork of Bayer interpolation?
     
    The Dude, Jan 7, 2004
    #19
  20. The Dude

    The Dude Guest

    "Dave Martindale" <> wrote in message
    news:btg50c$9k1$...
    > "The Dude" <.> writes:
    >
    > >Again,
    > >no meaningful difference once the medium file was ressed up. I repeated

    the
    > >exact same observations with the Canon 300D. Please repeat these tests
    > >yourselves and let mw know your opinions. This revelation will save lots

    of
    > >HD space and permit far more images on CF.

    >
    > When you reduce the size from 6 to 3 MP, the maximum possible linear
    > resolution is reduced to 70% of what it was. Now, the full-size image
    > may not have actual detail up to that limit, because the anti-aliasing
    > filter necessarily removes some fine detail below the theoretical limit.
    > When you downsize to 3 MP, you're using a digital filter that can be a
    > bit better about keeping information than the physical AA filter. Thus,
    > the 6 MP image may not lose as much as you'd expect, because it's
    > somewhat weak on that high-frequency detail in the first place.
    >
    > However, there is *some* loss, if the original is sharp. For example:
    > go to http://www.dpreview.com/reviews/canoneos300d/page21.asp and
    > download the upper left full-size test chart. Look at the resolution
    > test section just to the right of centre, a sort of sloping wedge.
    > There's another wedge above that too, for testing horizontal resolution.
    > Look and see how far along the wedges you can go and still see 9 clearly
    > resolved black bars. You'll have to view the image at 100% scale at
    > least to make any judgements. I'd say the limit on this particular test
    > is somewhere between 14 and 15, which means 1400-1500 lines per picture
    > height. (Note that this isn't the resolution limit, just a point up to
    > which I know I can get clean images without artifacts).


    True enough. There is measurable loss.
     
    The Dude, Jan 7, 2004
    #20
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