How much can I zoom?

Discussion in 'Digital Photography' started by keskew@comcast.net, Sep 21, 2006.

  1. Guest

    I am trying to find a formula or table that will enable me to predict
    how much I can zoom in on a digital photograph until it becomes
    unviewable. I know this seems vague so an example of what I mean might
    help.

    Let's say I have a circuit board that is X inches by Y inches in
    dimension. I take a picture of the circuit board using a digital
    camera with a resolution of Z mega-pixels so that the board fills the
    entire picture. Once I download the picture to my computer I want to
    be able to zoom in so that I can see the individual components on the
    circuit board. How much can I zoom in until the image becomes too
    grainy to make out the individual components?

    I know it has to do with the camera resolution and pixels-per-inch
    (ppi). I am not necessarily looking for a precise formula, but more of
    a reference guide. This is outside my realm of experience so any help
    is greatly appreciated.
    , Sep 21, 2006
    #1
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  2. Clive Guest

    I think you need to take some test shots.

    Also, megapixels aren't always the key. I could take a photo with a 17
    megapixel body without the lens on it. Although the image will be
    17megapixels, the image will not show anything. So, lens choice is very
    important.



    <> wrote in message
    news:...
    >I am trying to find a formula or table that will enable me to predict
    > how much I can zoom in on a digital photograph until it becomes
    > unviewable. I know this seems vague so an example of what I mean might
    > help.
    >
    > Let's say I have a circuit board that is X inches by Y inches in
    > dimension. I take a picture of the circuit board using a digital
    > camera with a resolution of Z mega-pixels so that the board fills the
    > entire picture. Once I download the picture to my computer I want to
    > be able to zoom in so that I can see the individual components on the
    > circuit board. How much can I zoom in until the image becomes too
    > grainy to make out the individual components?
    >
    > I know it has to do with the camera resolution and pixels-per-inch
    > (ppi). I am not necessarily looking for a precise formula, but more of
    > a reference guide. This is outside my realm of experience so any help
    > is greatly appreciated.
    >
    Clive, Sep 21, 2006
    #2
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  3. <> wrote in message
    news:...

    >I am trying to find a formula or table that will enable me to predict
    > how much I can zoom in on a digital photograph until it becomes
    > unviewable. I know this seems vague so an example of what I mean might
    > help.
    >
    > Let's say I have a circuit board that is X inches by Y inches in
    > dimension. I take a picture of the circuit board using a digital
    > camera with a resolution of Z mega-pixels so that the board fills the
    > entire picture. Once I download the picture to my computer I want to
    > be able to zoom in so that I can see the individual components on the
    > circuit board. How much can I zoom in until the image becomes too
    > grainy to make out the individual components?
    >
    > I know it has to do with the camera resolution and pixels-per-inch
    > (ppi). I am not necessarily looking for a precise formula, but more of
    > a reference guide. This is outside my realm of experience so any help
    > is greatly appreciated.


    Once you go over 100% the picture will simply pixellate so you will not be
    able to keep zooming in like they do in spy movies to see tiny details!

    You would be better off buying a microscope!
    Adrian Boliston, Sep 21, 2006
    #3
  4. Guest

    Experimentation (test shots) was my last option. I was hoping that a
    rule of thumb already existed.

    We do this quit often and you can zoom in pretty far and make out
    individual components, wire traces, etc. The problem is that we have
    never quantified it. I also know they sell special equipment and
    microscopes. These pictures are more for engineering reference than
    inspection.
    , Sep 21, 2006
    #4
  5. Clive Guest

    Why?

    Take a memory card into a store along with your circuit board and ask they
    if you can take some shots to see how they come out. Then, when you get
    home, look at the shots and decide.

    What you are asking in your OP is crazy, as there are so many variables.


    <> wrote in message
    news:...
    > Experimentation (test shots) was my last option. I was hoping that a
    > rule of thumb already existed.
    >
    > We do this quit often and you can zoom in pretty far and make out
    > individual components, wire traces, etc. The problem is that we have
    > never quantified it. I also know they sell special equipment and
    > microscopes. These pictures are more for engineering reference than
    > inspection.
    >
    Clive, Sep 21, 2006
    #5
  6. sally Guest

    In article <>,
    <> wrote:
    >I am trying to find a formula or table that will enable me to predict
    >how much I can zoom in on a digital photograph until it becomes
    >unviewable.


    Depends greatly on the quality of your equipment and also the quality of
    your zooming algorithm. If you can optimizing your zooming algorithm for
    your subject matter, you may be able to improve your results substantially
    (though it may sometimes guess wrong).
    sally, Sep 21, 2006
    #6
  7. Bill Funk Guest

    On Thu, 21 Sep 2006 20:38:19 +0100, "Adrian Boliston"
    <> wrote:

    ><> wrote in message
    >news:...
    >
    >>I am trying to find a formula or table that will enable me to predict
    >> how much I can zoom in on a digital photograph until it becomes
    >> unviewable. I know this seems vague so an example of what I mean might
    >> help.
    >>
    >> Let's say I have a circuit board that is X inches by Y inches in
    >> dimension. I take a picture of the circuit board using a digital
    >> camera with a resolution of Z mega-pixels so that the board fills the
    >> entire picture. Once I download the picture to my computer I want to
    >> be able to zoom in so that I can see the individual components on the
    >> circuit board. How much can I zoom in until the image becomes too
    >> grainy to make out the individual components?
    >>
    >> I know it has to do with the camera resolution and pixels-per-inch
    >> (ppi). I am not necessarily looking for a precise formula, but more of
    >> a reference guide. This is outside my realm of experience so any help
    >> is greatly appreciated.

    >
    >Once you go over 100% the picture will simply pixellate so you will not be
    >able to keep zooming in like they do in spy movies to see tiny details!
    >
    >You would be better off buying a microscope!
    >

    BINGO! We have a winnah!

    100% is the right answer.

    Just about any image viewer will let you zoom in to 100%; beyond that,
    pixelation set in.
    --
    Bill Funk
    replace "g" with "a"
    Bill Funk, Sep 21, 2006
    #7
  8. Mark² Guest

    wrote:
    > I am trying to find a formula or table that will enable me to predict
    > how much I can zoom in on a digital photograph until it becomes
    > unviewable. I know this seems vague so an example of what I mean
    > might help.
    >
    > Let's say I have a circuit board that is X inches by Y inches in
    > dimension. I take a picture of the circuit board using a digital
    > camera with a resolution of Z mega-pixels so that the board fills the
    > entire picture. Once I download the picture to my computer I want to
    > be able to zoom in so that I can see the individual components on the
    > circuit board. How much can I zoom in until the image becomes too
    > grainy to make out the individual components?
    >
    > I know it has to do with the camera resolution and pixels-per-inch
    > (ppi). I am not necessarily looking for a precise formula, but more
    > of a reference guide. This is outside my realm of experience so any
    > help is greatly appreciated.


    Once you reach the pixel level (100%), you're done.

    --
    Images (Plus Snaps & Grabs) by Mark² at:
    www.pbase.com/markuson
    Mark², Sep 22, 2006
    #8
  9. wrote:
    : I am trying to find a formula or table that will enable me to predict
    : how much I can zoom in on a digital photograph until it becomes
    : unviewable. I know this seems vague so an example of what I mean might
    : help.

    : Let's say I have a circuit board that is X inches by Y inches in
    : dimension. I take a picture of the circuit board using a digital
    : camera with a resolution of Z mega-pixels so that the board fills the
    : entire picture. Once I download the picture to my computer I want to
    : be able to zoom in so that I can see the individual components on the
    : circuit board. How much can I zoom in until the image becomes too
    : grainy to make out the individual components?

    : I know it has to do with the camera resolution and pixels-per-inch
    : (ppi). I am not necessarily looking for a precise formula, but more of
    : a reference guide. This is outside my realm of experience so any help
    : is greatly appreciated.

    Let me see if I can help you understand why you are getting the responses
    you are.

    If you are shooting an image of a board that is 8" x 10" and then print it
    out as an 8x10 print you would get a 1:1 magnification. But if the numbers
    printed on any single component is imaged by a single pixel each number
    would be a single dot at most. Very hard to read. So even if you "blow up"
    the image to a higher magnification you will still have each number on the
    component represented by a single dot. At a minimum you will probably need
    each number to be represented by 6 to 9 pixels to have any chance at all
    of reading the numbers. And even this will not be easy to read.

    Now if you shoot a similar image of a board that is only 4" x 5", each
    pixel will only be covering 1/4 the area of the board of the prior image.
    And so you will be able to resolve details 4 x smaller than previously.
    Notice the number of pixels and the "zoom" on the screen have little to do
    with the readability of the number. It is much more a case of how many
    pixels will image the number. So it will be the magnification (and
    clarity) of the macro lens, plus the size of the area being imaged, plus
    the size of the area that is used by each individual number to be read,
    and only then the number of pixels in the entire image, that will go into
    being able to read the numbers on the components.

    BTW the responses of 100% zoom are also mostly correct. When you "zoom in"
    on an image with an editor you can only get up to 1 pixel being displayed
    by one dot on the screen (for the purists, one "dot" being composed of one
    red, one green and one blue phosphor). Once you go above that zoom you
    will get a distorted image. Straight lines will zig-zag, and thin lines
    will become long rows of blobs. It is possible to zoom slightly beyond
    100% which will make the image larger on the screen, but the distortion
    will get larger and larger until it is difficult or impossible to
    recognize anything. Depending on your ability to mentally decode the blurs
    and blobs you may be able to zoom higher than someone else. But in general
    you won't be going much beyond 100 to 110%, IMHO. But this zoom
    number is a relationship between the number of image pixels being
    displayed by each dot on the screen, and thus has no hard and fast
    relationship to the size of the object in real life to the size of the
    image on the screen. They are related, but not absolute.

    So to answer your simple question there would have to be lots of variables
    measured first. We would need to know ALL the parameters of the lens (and
    there are a LOT of them). Then we would need to know the exact dimensions
    of the PC board to be imaged. Then we would have to know if you have the
    equipment to exactly position the board and camera to maximize the size of
    the board in the image. Then we would need the dimensions of the smallest
    number that will need to be read. Then (yes) the number of pixels per
    image. And lastly we would have to know (from experimentation) how many
    pixels per number will give us a readable image, consistantly. And after
    all that, the best we could give you is a "it MIGHT work" or a "probably
    not".

    My best advice is to experiment. Borrow a camera and see how close you
    have to get to get a consistant read of the numbers and measure the size
    of that the image covers on the original image. Then divide these
    dimensions into the total dimensions of the full sized board and then
    multiply that result by the number of pixels in the test image. Work each
    dimension (Horiz, Vert) seperately. This would be a good aprox pixel count
    target for choosing a possible camera. Then give it a try with your
    fingers crossed.

    Good luck

    Randy

    ==========
    Randy Berbaum
    Champaign, IL
    Randy Berbaum, Sep 22, 2006
    #9
  10. writes:
    >I am trying to find a formula or table that will enable me to predict
    >how much I can zoom in on a digital photograph until it becomes
    >unviewable. I know this seems vague so an example of what I mean might
    >help.


    It's actually not that difficult to do the calculations for this. All
    you need is a calculator.

    First, you need to know the size of the image produced by the camera in
    pixels. There is a formula to calculate X and Y resolution given the
    number of megapixels and the image aspect ratio, but most camera reviews
    give the image size in pixels directly, so let's assume you can get
    that. For an example, assume you have a 6 megapixel DSLR whose output
    image is 3072x2048 pixels.

    When you photograph a circuit board, you first have to figure out how
    the board will fit the image. A square board will fill the image height
    but leave 1/3 of the width unused. A long skinny board will fit the
    width but leave some of the height unused. Once you decide which
    dimension of the image will fit the board, divide the corresponding
    width/height of the image in pixels by the width/height of the board in
    inches to get a scale factor in pixels/inch.

    For example, suppose your board is 8x10 inches. At maximum size, this
    will fill the image height but not use the full width, so it is height
    that matters. The pixels/inch on the board is 2048/8 = 256. So you get
    256 pixels per inch, or every pixel is 0.0039 inches.

    So you will be able to *see* all of the parts on the board as long as
    they are more than a few thousandths of an imch in size. But to be able
    to read lettering on the components, the letters should be somewhere
    near 10 pixels high.

    If your resistors are "0406" size, 0.040 by 0.060 inches in size, that's
    about 10x15 pixels when the image is displayed at "100%" size. You
    definitely should be able to see the resistors, but being able to read
    the resistance value printed on top could be a challenge.

    On the other hand, if the board is 4x5 inches, the pixel density doubles
    and reading small text becomes much easier

    Dave
    Dave Martindale, Sep 22, 2006
    #10
  11. Guest

    Thanks to everyone who responded, especially Randy Berbaum and Dave
    Martindale. You guys confirmed the conclusion I came to last night
    after continuing to work on this. I also did some experimentation.
    While it is true that the picture begins to "pixellate" after 100%,
    the images are still viewable (at least for my purposes) up to 200%.
    In some cases the pictures were viewable up to 250%. I believe this is
    because for the camera I was using, (Cannon Power Shot S2 IS - 5
    megapixel) at the highest settings it produced 8.3" X 11.7"
    pictures at approximately 220 ppi. That allows the picture to be
    enlarged to 200%, or greater, and be viewable, though certainly not
    photo quality. Thanks again.
    , Sep 22, 2006
    #11
  12. wrote:
    > Thanks to everyone who responded, especially Randy Berbaum and Dave
    > Martindale. You guys confirmed the conclusion I came to last night
    > after continuing to work on this. I also did some experimentation.
    > While it is true that the picture begins to "pixellate" after 100%,
    > the images are still viewable (at least for my purposes) up to 200%.
    > In some cases the pictures were viewable up to 250%. I believe this is
    > because for the camera I was using, (Cannon Power Shot S2 IS - 5
    > megapixel) at the highest settings it produced 8.3" X 11.7"
    > pictures at approximately 220 ppi. That allows the picture to be
    > enlarged to 200%, or greater, and be viewable, though certainly not
    > photo quality. Thanks again.
    >


    I think you'd also find, if your monitor were large enough, and you
    could get far enough away from it, that many low ppi counts would look
    fine. Same with printing; bill boards seem to be printed with inches per
    dot, not dots per inch! Although I exaggerate, a well done bill board
    looks great from the right distance.

    --
    john mcwilliams
    John McWilliams, Sep 22, 2006
    #12
  13. dmaster Guest

    wrote:
    > Thanks to everyone who responded, especially Randy Berbaum and Dave
    > Martindale. You guys confirmed the conclusion I came to last night
    > after continuing to work on this. I also did some experimentation.
    > While it is true that the picture begins to "pixellate" after 100%,
    > the images are still viewable (at least for my purposes) up to 200%.
    > In some cases the pictures were viewable up to 250%. I believe this is


    So far so good. Yes the pictures are going to be "viewable", meaning
    recognizable to some arbitrary magnification. But, that does not mean
    you are seeing anything new! Once your eyes can see the individual
    pixels...there is nothing more to see. Sure, zooming with make the
    original
    pixels bigger, but there is no more information to see.

    > because for the camera I was using, (Cannon Power Shot S2 IS - 5
    > megapixel) at the highest settings it produced 8.3" X 11.7"
    > pictures at approximately 220 ppi. That allows the picture to be
    > enlarged to 200%, or greater, and be viewable, though certainly not
    > photo quality. Thanks again.


    Ick. You've run off the rails. The "ppi" of the file the camera
    produces
    has absolutely nothing to do with your application. Heck, if you would
    sit twice as far from the monitor, you'd magically be able to zoom
    twice
    as much, and the image would still be viewable! But as I said above,
    this is pointless. Once you can distinguish every piece of information
    (pixels) nothing more can be gained.

    Ah... That may be what is misleading you... depending on your eyes
    and distance from the monitor, you may need to zoom well beyond
    100% to see every pixel.

    Dan (Woj...)
    dmaster, Sep 22, 2006
    #13
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