high optical vs. large megapixel ?

Discussion in 'Digital Photography' started by Andy, Jul 26, 2004.

  1. Andy

    Andy Guest

    Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    theoretically).

    This weekend i was at the Sunderland Airshow, i have a Fuji Finepix 2800Zoom
    (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    on the PC monitor (and no zooming in/out of picture) the plane looks to be
    about 7cm on screen. Now, what i am trying to find out is, forgetting
    picture QUALITY, would i have got similar results with a camera with only a
    3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    picture on screen, would the plane still look to be 7cm ?.

    Hope someone knows what i'm going on about !

    Cheers
    Andy
    Andy, Jul 26, 2004
    #1
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  2. Andy

    chesham Guest

    Hello, I can see where you are coming from ... but I haven't a clue on this
    one!

    I tend to say that high pixel is better in low light conditions ... and the
    zoom is of better use in the better lighting!

    Just be sure that you AVOID digital zoom ... OK!


    Jon


    "Andy" <> wrote in message
    news:ce3aj5$84v$...
    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).
    >
    > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix

    2800Zoom
    > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    > on the PC monitor (and no zooming in/out of picture) the plane looks to be
    > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > picture QUALITY, would i have got similar results with a camera with only

    a
    > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > picture on screen, would the plane still look to be 7cm ?.
    >
    > Hope someone knows what i'm going on about !
    >
    > Cheers
    > Andy
    >
    >
    chesham, Jul 26, 2004
    #2
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  3. Andy

    Andy100 Guest

    Yeah, thanks for the info. I do tend to stay well clear of digital zoom,
    because I, probably like many others fell into the trap of using it only to
    find out it's horrible !!

    Cheers
    Andy


    "chesham" <> wrote in message
    news:ce3bpt$8pp$...
    > Hello, I can see where you are coming from ... but I haven't a clue on

    this
    > one!
    >
    > I tend to say that high pixel is better in low light conditions ... and

    the
    > zoom is of better use in the better lighting!
    >
    > Just be sure that you AVOID digital zoom ... OK!
    >
    >
    > Jon
    >
    >
    > "Andy" <> wrote in message
    > news:ce3aj5$84v$...
    > > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > > theoretically).
    > >
    > > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix

    > 2800Zoom
    > > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the

    picture
    > > on the PC monitor (and no zooming in/out of picture) the plane looks to

    be
    > > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > > picture QUALITY, would i have got similar results with a camera with

    only
    > a
    > > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > > picture on screen, would the plane still look to be 7cm ?.
    > >
    > > Hope someone knows what i'm going on about !
    > >
    > > Cheers
    > > Andy
    > >
    > >

    >
    >
    Andy100, Jul 26, 2004
    #3
  4. Andy

    Matt Ion Guest

    "Andy" <> wrote in message
    news:ce3aj5$84v$...
    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).


    Absolutely not.

    For starters, magnifaction ratings can mean two different things, and in
    either case, it's a relative reading. In the case of zoom lenses, or lenses
    with adjustable magnification, which is what we're dealing with here, it's
    simply a comparison between the highest and lowest magnification factor. A
    higher rating (6X) means you have a wider range between the lens's
    wide-angle and close-up settings.

    The other measurement is used for fixed-magnification devices like
    binoculars, telescopes, microscopes, etc. and refers to excatly how much an
    object is magnified, which is probably what you're thinking of, but that
    doesn't apply to cameras of any sort, because the final output can affect
    the size of an object in the picture as well.

    Second, megapixels is only half the story when it comes to sensors; the
    actual size of the sensor affects things as well.

    A certain lens's magnification depends first of all on the size of the
    target area. I'm a little rusty on the math, so if I'm off, someone correct
    me (nicely), but as I recall... magnification can be calculated by focal
    length divided by the diagonal of the target frame. A 35mm film frame has a
    diagonal of around 55mm, so a standard 50mm lens gives you very close to 1X
    (or 1:1) magnification. A 100mm lens would be 2X, 200mm would be 4X, and so
    on.

    When you get into digital sensors, they're typically smaller than 35mm film,
    so the magnification for a specific lens length increases. Say your sensor
    is 33mm diagonally; a 100mm lens would then be about 3X magnification and
    show a smaller area than the same lens on a 35mm camera.

    For a given size of sensor, magnification will always be the same for a
    given lens regardless of megapixels, but the actual size of the image in
    pixels will vary. As a direct comparison, my Kodak 3.2MP camera output
    images of 2080x1544; my Canon 6.3MP camera outputs at 3072x2048. For the
    sake of argument, say the sensor is the same size, and the lens the same
    length, on both cameras: both will then take the exact same image, area-wise
    (same magnification).

    The Kodak camera, however, breaks it into fewer pieces, so each piece is
    going to be larger than with the Canon. If you resized the Kodak image to
    match the pixel size of the Canon, you'd find the picture a fair bit noiser,
    with rougher edges to objects, because those 3.2 million bits of picture
    must be expanded by an uneven factor.

    > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix

    2800Zoom
    > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    > on the PC monitor (and no zooming in/out of picture) the plane looks to be
    > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > picture QUALITY, would i have got similar results with a camera with only

    a
    > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > picture on screen, would the plane still look to be 7cm ?.


    Again, in this usage, zoom factor refers only to the range of the lens from
    shortest to longest focal length. Using the numbers above, a lens that
    zooms from 50mm to 200mm would be a "4X optical zoom", regardless of the
    actual magnification numbers: magnification will be four times greater at
    the tightest angle than at the widest angle.

    Higher megapixels will let you get away with a shorter lens for the same
    quality pictures, but exactly how it affects your example above depends on
    the actual magnification involved, which will depend on the relative sizes
    of the two cameras' sensors, and the precise zoom setting you're using.
    Matt Ion, Jul 26, 2004
    #4
  5. Andy

    Ol' Bab Guest

    Andy wrote:

    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).
    >

    By 6x zoom, I'm betting you mean "a lens with twice the
    maximum focal length"

    No, the number you'd get is 1.25 Mp -ie, one quarter. The
    resolution IS doubled but the pixel count is SQUARED.

    This assumes your targets of choice are songbirds at a feeder
    across the parking lot, and you can't get closer, so whatever
    camera you use, the results must be cropped.

    So if you just can't move closer, a LONG telephoto (say 4x
    longer) will save a thunder of money: make your 5 Mp act like
    an 80 Mp !! Of course now you need a tripod, and the flash is
    hopeless.

    Trade-offs, trade-offs.

    Ol' Bab
    Ol' Bab, Jul 26, 2004
    #5
  6. "Andy" <> wrote in news:ce3aj5$84v$:

    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).


    That depends on what you are planning to photo.

    If it is something that fills the frame and where
    you want to be able to make larger prints - no.

    If it is song birds that fills just a small bit
    of the actual frame, you can actually get away with
    1.5 Mpixels at 6x zoom.

    But - in the latter case - 20x zoom would be better.


    /Roland
    Roland Karlsson, Jul 26, 2004
    #6
  7. Andy wrote:
    > Pardon my ignorance, but am i right in thinking that a camera with a
    > 3 X Optical Zoom having 5MPixels, is about the same as a camera
    > having a 6 X Optical Zoom with 2.5MPixels (i know you don't often get
    > 2.5MP, but just theoretically).
    >
    > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix
    > 2800Zoom (2.0MP, 6X Optical), i got reasonable pictures, and looking
    > at the picture on the PC monitor (and no zooming in/out of picture)
    > the plane looks to be about 7cm on screen. Now, what i am trying to
    > find out is, forgetting picture QUALITY, would i have got similar
    > results with a camera with only a 3X optical zoom, but having 4 or
    > 5MP ? (i.e. without any zooming of the picture on screen, would the
    > plane still look to be 7cm ?.
    >
    > Hope someone knows what i'm going on about !
    >
    > Cheers
    > Andy


    As, Ol' Bab pointed out, no. In addition with the 5MP camera you also
    have the option of using it at 3X or less and getting the full 5MP and the
    option of cropping it at your leisure if you like or using the full 5MP


    --
    Joseph E. Meehan

    26 + 6 = 1 It's Irish Math
    Joseph Meehan, Jul 26, 2004
    #7
  8. Andy

    Si Guest

    your ignorance has been pardonned

    take everything above with a pinch of salt

    Si

    "Andy" <> wrote in message
    news:ce3aj5$84v$...
    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).
    >
    > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix

    2800Zoom
    > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    > on the PC monitor (and no zooming in/out of picture) the plane looks to be
    > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > picture QUALITY, would i have got similar results with a camera with only

    a
    > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > picture on screen, would the plane still look to be 7cm ?.
    >
    > Hope someone knows what i'm going on about !
    >
    > Cheers
    > Andy
    >
    >
    Si, Jul 27, 2004
    #8
  9. On Mon, 26 Jul 2004 17:13:38 +0100, "Andy" <>
    wrote:

    >Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    >Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    >Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    >theoretically).


    Andy,

    Ol' Bab already wrote it, and Joseph reinforced it. Your thought
    is correct for max zoom shots including 2 x digital zoom for the
    3 x optical zoom camera.

    However, the mathematics are wrong. You'd need 10 Megapixels to
    arrive at the same 2.5 Megapixel photo.

    However, at shorter zoom settings the two cameras would be
    different. The one with the more pixels would deliver photos
    with more genuine pixels.

    Hans-Georg

    --
    No mail, please.
    Hans-Georg Michna, Jul 27, 2004
    #9
  10. Andy

    Andy100 Guest

    Thanks for all the info (wish i'd never asked !!)

    Cheers
    Andy


    "Hans-Georg Michna" <> wrote in message
    news:...
    > On Mon, 26 Jul 2004 17:13:38 +0100, "Andy" <>
    > wrote:
    >
    > >Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > >Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > >Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > >theoretically).

    >
    > Andy,
    >
    > Ol' Bab already wrote it, and Joseph reinforced it. Your thought
    > is correct for max zoom shots including 2 x digital zoom for the
    > 3 x optical zoom camera.
    >
    > However, the mathematics are wrong. You'd need 10 Megapixels to
    > arrive at the same 2.5 Megapixel photo.
    >
    > However, at shorter zoom settings the two cameras would be
    > different. The one with the more pixels would deliver photos
    > with more genuine pixels.
    >
    > Hans-Georg
    >
    > --
    > No mail, please.
    Andy100, Jul 27, 2004
    #10
  11. Andy

    Terence Guest

    "Matt Ion" <> wrote in message news:<SYdNc.119499$ek5.61064@pd7tw2no>...

    [snip]
    > > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    > > on the PC monitor (and no zooming in/out of picture) the plane looks to be
    > > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > > picture QUALITY, would i have got similar results with a camera with only

    > a
    > > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > > picture on screen, would the plane still look to be 7cm ?.

    >
    > Again, in this usage, zoom factor refers only to the range of the lens from
    > shortest to longest focal length. Using the numbers above, a lens that
    > zooms from 50mm to 200mm would be a "4X optical zoom", regardless of the
    > actual magnification numbers: magnification will be four times greater at
    > the tightest angle than at the widest angle.
    >
    > Higher megapixels will let you get away with a shorter lens for the same
    > quality pictures, but exactly how it affects your example above depends on
    > the actual magnification involved, which will depend on the relative sizes
    > of the two cameras' sensors, and the precise zoom setting you're using.


    This is something I've always wondered as well, and while I realize
    that there are many additional factors involved in calculating the
    final absolute magnification level, I'm assuming it's safe to say that
    -all else being equal- if, for example, we used the same exact camera
    body/sensor/lens to take 2 identical shots, one at 3.2mp (2048x1536),
    and one at 5.0mp (2592x1944), you are effectively achieving a 1.6x
    increase in magnification, since you can crop the 5mp image to 3.2mp
    dimensions, producing a "zoomed in" image, while printing at the same
    ppi.
    Terence, Jul 27, 2004
    #11
  12. Andy

    Don Stauffer Guest

    Only if the only reason you have the camera is to shoot objects at
    inaccessible distances.

    I personally would rather have the 5MP camera. I still shoot most of my
    pictures with a 'normal' focal length, and want as many pixels in my
    image as possible, regardless of the focal length I am using.

    Andy wrote:
    >
    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).
    >
    > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix 2800Zoom
    > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    > on the PC monitor (and no zooming in/out of picture) the plane looks to be
    > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > picture QUALITY, would i have got similar results with a camera with only a
    > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > picture on screen, would the plane still look to be 7cm ?.
    >
    > Hope someone knows what i'm going on about !
    >
    > Cheers
    > Andy


    --
    Don Stauffer in Minnesota

    webpage- http://www.usfamily.net/web/stauffer
    Don Stauffer, Jul 27, 2004
    #12
  13. Andy

    Andy100 Guest

    Yeah, same here. I just take usual run of the mill pics, but occasionally I
    do need to get close in on the action, such as the Sunderland Airshow last
    weekend. But i think i'll make do with my 2800Z for the time being which did
    give me pretty good results at 6X Optical anyway ! (was thinking about
    upgrading to the Fuji FinePix S5000 or S7000, any comments there ??)

    Cheers
    Andy


    "Don Stauffer" <> wrote in message
    news:...
    > Only if the only reason you have the camera is to shoot objects at
    > inaccessible distances.
    >
    > I personally would rather have the 5MP camera. I still shoot most of my
    > pictures with a 'normal' focal length, and want as many pixels in my
    > image as possible, regardless of the focal length I am using.
    >
    > Andy wrote:
    > >
    > > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > > theoretically).
    > >
    > > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix

    2800Zoom
    > > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the

    picture
    > > on the PC monitor (and no zooming in/out of picture) the plane looks to

    be
    > > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > > picture QUALITY, would i have got similar results with a camera with

    only a
    > > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > > picture on screen, would the plane still look to be 7cm ?.
    > >
    > > Hope someone knows what i'm going on about !
    > >
    > > Cheers
    > > Andy

    >
    > --
    > Don Stauffer in Minnesota
    >
    > webpage- http://www.usfamily.net/web/stauffer
    Andy100, Jul 27, 2004
    #13
  14. Depends upon whether you would rather keep the highlights or have them blown

    Personally I would prefer to keep highlights - tonal variations in the sky
    may compliment the pics you wish to take

    Arty

    "Andy100" <> wrote in message
    news:ce6bbf$irr$...
    > Yeah, same here. I just take usual run of the mill pics, but occasionally

    I
    > do need to get close in on the action, such as the Sunderland Airshow last
    > weekend. But i think i'll make do with my 2800Z for the time being which

    did
    > give me pretty good results at 6X Optical anyway ! (was thinking about
    > upgrading to the Fuji FinePix S5000 or S7000, any comments there ??)
    >
    > Cheers
    > Andy
    >

    <snipped to save server space>
    Arty Phacting, Jul 29, 2004
    #14
  15. Andy wrote:
    >
    > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > theoretically).
    >
    > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix 2800Zoom
    > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the picture
    > on the PC monitor (and no zooming in/out of picture) the plane looks to be
    > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > picture QUALITY, would i have got similar results with a camera with only a
    > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > picture on screen, would the plane still look to be 7cm ?.
    >
    > Hope someone knows what i'm going on about !
    >
    > Cheers
    > Andy


    Andy,

    I have been making the same calculations, when I went to the Farnborough
    airshow last weekend ... but you make a small mistake here:

    Double the Pixels only makes the image 1.4 times as big (Square root of
    2)
    So, you could compare an increase from 2.5 to 5 MPixel to an increase in
    Optical zoom of say ... from 3x to 4.2x.
    But ... that is Digital zoom, only, you are doing it at home on your
    computer.

    so ... 6x optical zoom on 2.0 MPixel would result in the same size
    airplane (in pixels) as a 5 MPixel image with:

    5/2 = 2.5
    Square root of 2.5 = 1.6
    New zoom = 6/1.6 = 3.75x

    You 'forgot' the square root. This thing comes from this:
    If you make a picture twice as large, say 10x10 pixels -> 20x20 pixels,
    the amount of pixels go from 10x10=100 to 20x20=400 pixels. That is not
    2 times, but 4 times as many!

    So if you have double the size, you have 4 times the pixels.
    Or the other way around,
    If you have double the pixels, you only have Square root of 2 = 1.4
    times the size of your photo ...


    One more thing about the 'times zoom' that is indicated on cameras:
    The Canon A70 has 3 times zoom. 35-105 mm
    The Canon S60 has 3.6 times zoom. 28-100 mm

    So, even though the 'times zoom' on the S60 is bigger, the size of the
    airplane is actually smaller!!! If you want to compare the size of the
    airplane on a photo between cameras, you should look at the 'amount of
    tele'. For the A70 that would be 105mm, and for the S60 that would be
    100mm.

    Luckily the S60 has way more pixels than the A70, so the smaller tele is
    compensated ;-)

    Have fun,

    Wouter
    Wouter Wessels, Aug 1, 2004
    #15
  16. In article <>,
    (Terence) wrote:

    > "Matt Ion" <> wrote in message
    > news:<SYdNc.119499$ek5.61064@pd7tw2no>...
    >
    > [snip]
    > > > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the
    > > > picture
    > > > on the PC monitor (and no zooming in/out of picture) the plane looks to
    > > > be
    > > > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > > > picture QUALITY, would i have got similar results with a camera with only

    > > a
    > > > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > > > picture on screen, would the plane still look to be 7cm ?.

    > >
    > > Again, in this usage, zoom factor refers only to the range of the lens from
    > > shortest to longest focal length. Using the numbers above, a lens that
    > > zooms from 50mm to 200mm would be a "4X optical zoom", regardless of the
    > > actual magnification numbers: magnification will be four times greater at
    > > the tightest angle than at the widest angle.
    > >
    > > Higher megapixels will let you get away with a shorter lens for the same
    > > quality pictures, but exactly how it affects your example above depends on
    > > the actual magnification involved, which will depend on the relative sizes
    > > of the two cameras' sensors, and the precise zoom setting you're using.

    >
    > This is something I've always wondered as well, and while I realize
    > that there are many additional factors involved in calculating the
    > final absolute magnification level, I'm assuming it's safe to say that
    > -all else being equal- if, for example, we used the same exact camera
    > body/sensor/lens to take 2 identical shots, one at 3.2mp (2048x1536),
    > and one at 5.0mp (2592x1944), you are effectively achieving a 1.6x
    > increase in magnification, since you can crop the 5mp image to 3.2mp
    > dimensions, producing a "zoomed in" image, while printing at the same
    > ppi.


    Terence,

    Don't forget the Square root.
    From 3.2 MPixel to 5 MPixel is a magnification of SquareRoot(5/3.2)=
    1.25 (approx)

    That is because the actual enlargement is not 3.2 -> 5.0 but
    2048 -> 2592 (or 1536 -> 1944)

    Wouter
    Wouter Wessels, Aug 1, 2004
    #16
  17. Andy

    Andy100 Guest

    Cheers Wouter, that has actually made it more clearer to me (of course,
    square root, i should have realised that !!)

    Cheers
    Andy



    "Wouter Wessels" <> wrote in message
    news:...
    >
    >
    > Andy wrote:
    > >
    > > Pardon my ignorance, but am i right in thinking that a camera with a 3 X
    > > Optical Zoom having 5MPixels, is about the same as a camera having a 6 X
    > > Optical Zoom with 2.5MPixels (i know you don't often get 2.5MP, but just
    > > theoretically).
    > >
    > > This weekend i was at the Sunderland Airshow, i have a Fuji Finepix

    2800Zoom
    > > (2.0MP, 6X Optical), i got reasonable pictures, and looking at the

    picture
    > > on the PC monitor (and no zooming in/out of picture) the plane looks to

    be
    > > about 7cm on screen. Now, what i am trying to find out is, forgetting
    > > picture QUALITY, would i have got similar results with a camera with

    only a
    > > 3X optical zoom, but having 4 or 5MP ? (i.e. without any zooming of the
    > > picture on screen, would the plane still look to be 7cm ?.
    > >
    > > Hope someone knows what i'm going on about !
    > >
    > > Cheers
    > > Andy

    >
    > Andy,
    >
    > I have been making the same calculations, when I went to the Farnborough
    > airshow last weekend ... but you make a small mistake here:
    >
    > Double the Pixels only makes the image 1.4 times as big (Square root of
    > 2)
    > So, you could compare an increase from 2.5 to 5 MPixel to an increase in
    > Optical zoom of say ... from 3x to 4.2x.
    > But ... that is Digital zoom, only, you are doing it at home on your
    > computer.
    >
    > so ... 6x optical zoom on 2.0 MPixel would result in the same size
    > airplane (in pixels) as a 5 MPixel image with:
    >
    > 5/2 = 2.5
    > Square root of 2.5 = 1.6
    > New zoom = 6/1.6 = 3.75x
    >
    > You 'forgot' the square root. This thing comes from this:
    > If you make a picture twice as large, say 10x10 pixels -> 20x20 pixels,
    > the amount of pixels go from 10x10=100 to 20x20=400 pixels. That is not
    > 2 times, but 4 times as many!
    >
    > So if you have double the size, you have 4 times the pixels.
    > Or the other way around,
    > If you have double the pixels, you only have Square root of 2 = 1.4
    > times the size of your photo ...
    >
    >
    > One more thing about the 'times zoom' that is indicated on cameras:
    > The Canon A70 has 3 times zoom. 35-105 mm
    > The Canon S60 has 3.6 times zoom. 28-100 mm
    >
    > So, even though the 'times zoom' on the S60 is bigger, the size of the
    > airplane is actually smaller!!! If you want to compare the size of the
    > airplane on a photo between cameras, you should look at the 'amount of
    > tele'. For the A70 that would be 105mm, and for the S60 that would be
    > 100mm.
    >
    > Luckily the S60 has way more pixels than the A70, so the smaller tele is
    > compensated ;-)
    >
    > Have fun,
    >
    > Wouter
    Andy100, Aug 1, 2004
    #17
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