True 10X optical zoom?

Discussion in 'Digital Photography' started by Don, Nov 23, 2003.

  1. Don

    Don Guest

    I just purchased a Minolta Dimage Z1. I only had it for a day, it's
    my first digital camera and I know nothing about photography, but I'm
    already creating great pictures with it.

    But I was curious as to why the 10X zoom is not quite as powerful as a
    pair of 10X binoculars I have. At full optical zoom on the camera, I
    get very crisp, clear pictures, but I noticed a sign off in the
    distance that is not quite close enough in the printed picture to make
    out the writing. The sign is readable through the binoculars, but
    with the binoculars the sign appears to be much closer than the print
    from the camera.

    I used glossy photo paper and had the camera set to it's highest
    resolution, printing at the same resolution, but this doesn't appear
    to be a matter of resolution or clarity. The printed image really
    doesn't appear to be as close as the binoculars.

    I would assume a rating of 10X is standard on any instrument.
    Am I missing something here or is that just the nature of a camera's
    zoom as compared to the telescoping effect of other instruments.

    Don
     
    Don, Nov 23, 2003
    #1
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  2. Don

    Don Guest

    I think I'll respond to my own posting. I should have mentioned that
    the print I made was 4X6. Now I'm thinking that had I made a full
    8X10 I may get a different perspective.

    I'll give that a try before I start knocking the zoom capability of
    this camera.

    Don
     
    Don, Nov 23, 2003
    #2
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  3. 10x refers to the multiplication factor between the widest focal length
    of the lens and the telephoto focal length.

    Thus a 35-70 zoom could be referred to as a 2x lens. A 38-380 lens
    would be a 10X zoom lens.

    I don't think there is any standard of magification between binoculars,
    cameras or video cameras. I could be wrong but in my experience this
    seems to be the case.
     
    Andrew McDonald, Nov 23, 2003
    #3
  4. Don

    Don Guest

    Thank you. I did just print a 7.5X10 and that only opened a new can
    of worms. I was originally going to purchase a 4MP camera, but
    decided on the Minolta Z1 when the person helping me said a 3.2 pixel
    will print fine up to 8X10 without losing any clarity.

    That is not the case in my situation. The 4X6 is very clear, but the
    larger printout loses a LOT of resolution.

    Don
     
    Don, Nov 23, 2003
    #4
  5. Don

    Andy Hewitt Guest

    Actually, there is a standard. In traditional SLR photography they never
    stated the zoom factor, only the focal length, or range of focal length.
    As a rule it roughly equated that 1x zoom was about 50mm (it was
    actually about 49mm). This offered a field of view roughly what you see
    with the naked eye. Thus a 500mm lens was about 10x magnification. As
    far as I know binoculars and telecopes work much the same way.

    As far as digital cameras go, you are correct, they simply divide the
    highest focal length by the lowest. However, the focal length of a
    digital camera is not the same as it is with traditional optics, so you
    have to convert them anyway.

    You have to watch these things quite carefully now, as this kind of
    false specification is popping up everywhere. I only found out a few
    days ago that the dpi rating of a printer is in fact the *total' number
    of pixels created by all of the print heads, so you have to divide the
    dpi by the number of print heads to get the true dpi rating.
     
    Andy Hewitt, Nov 23, 2003
    #5
  6. Don

    Jim Townsend Guest

    Zoom is the difference between maximum and minimum focal length. It has
    nothing to do with magnification.

    In 35mm terms, your Z1 has an equivalent focal length of 38mm on the wide end
    and 380mm on the telephoto.

    So.. if you divide: 380mm max by 38mm min, you get 10. The maximum focal
    length is 10 times more than the minimum. That's how the zoom is calculated.
    Think of zoom as motion. (ie zooming in, zooming out). The 'X' in the zoom
    rating shows how much the lens can -move- not magnify.

    A fixed lens has no zoom at all since you can't move it.

    Magnification gets tricky. In 35mm terms, (and only 35mm terms), a focal
    length of about 50mm is thought to most closely approximate what our eyes see.
    In other words 50mm gives you a magnification of exactly 1X..

    By dividing the total focal length, you can roughly determine the magnification
    of a lens. So your longest focal length (380mm) would provide 380/50= 7.6X
    magnification.
     
    Jim Townsend, Nov 23, 2003
    #6
  7. Don

    Mike O Guest

    To expand, as I figure it, the 10x like he said refers to 10x 38mm in the
    example Andrew gave. If your binoculers say 10x, its probably 10x
    magnification...not a measurement you can compare.

    Not positive but this sounds right to me at least :-}

    Mike
    -
     
    Mike O, Nov 23, 2003
    #7
  8. Don

    Andy Hewitt Guest

    Hmmm, are you sure it's not your printer settings. I have some images I
    printed onto A4 from my old Olympus C960z (a 1.3MP camera), and they are
    certainly quite acceptable.

    Don't forget you need to change the resolution of the image from the
    72dpi screen resolution (which is what comes out of the camera) to
    something like 300dpi for the printer.
     
    Andy Hewitt, Nov 23, 2003
    #8
  9. Don

    Don Guest

    Andy,

    Interesting you should point that out regarding the pixels. As I
    mentioned, my 7.5 X 10 printout lost a lot of resolution after the
    salesperson told me this 3.2 pixel camera would not at that size.

    But I just checked my printer's specs and see that although I shot the
    scene at 2048 X 1764, my printer supports a maximum resolution of 4800
    X 1200. Although the printer rates this as 5.8 MP, which is correct
    and my camera is only 3.2 MP, the horizontal or vertical resolution
    of the scene I shot is outside what my printer (Lexmark Z65) supports.
    So I guess that problem is not with the camera, but with the printer.

    Don
     
    Don, Nov 23, 2003
    #9
  10. Don

    Don Guest

    Thanks. I get the idea now from these replies. I guess it's not the
    problem I thought it was, then. I was comparing apples to whatever.
    I'm perfectly happy with the amount of zoom and probably even more
    satisfied now that you've all expalined that it isn't a shortcoming on
    the part of the camera.
     
    Don, Nov 23, 2003
    #10
  11. Don

    Ray Fischer Guest

    In one case "10x" refers to ten times magnification over what your eye
    normally sees. In the other case "10x" refers to the difference
    between the lowest and the highest magnification.

    The camera's lowest magnification is a wider angle view than you'd
    normally see with your eyes.
     
    Ray Fischer, Nov 23, 2003
    #11
  12. I'm not too aware of binocular terminology, but I assume the given
    magnification factor is vs. the diagonal of the projected area. In 35mm
    photography, the standard lens is 50mm as this is fairly close to the
    diagonal of a 36x24mm section of film. Therefore a 10x magnification of this
    would require a 500mm lens, which is what I assume would give a similar
    field of view as your binoculars.
    In zoom lens terminology, a magnification factor (not a common thing in
    "serious" photographic terminology) is based on the relation of the extreme
    ends of the focal range. i.e. a 35-70mm zoom is a 2x zoom and a 28-210mm is
    a 7.5x zoom. IIRC the A1 has a lens equivalent to a 38-380 or 35-350mm lens
    in 35mm terms, which (assuming my earlier statement is correct) would be
    similar to a 7x or 7.5x magnification pair of binos.
     
    Martin Francis, Nov 23, 2003
    #12
  13. I have printed many a decent 8x10 from my 3MP Coolpix 990. So it may
    not the be megapixels but some other factor affecting how your picture
    looks.

    Something to consider is that a 10x zoom lens sometimes sacrifices
    qualitly to achieve that zoom ratio. I have read that 2-3x is the most
    you want to attempt in a "good" zoom lens, thus the 70-200 or 80-200
    ranges in 35mm lenses.

    At 10x (380mm) you need at LEAST a 400th of a second to prevent camera
    shake. And that assumes proper technigue when holding the camera, no
    wind or other vibrations. Hopefully the camera is using as fast a
    shutter speed as it can but depending on the aperature you get stuck
    with when using the zoom at 10x there may only be so much the camera can
    do. So you might just be seeing camera shake.

    You also are not going to have alot of cropping room doing an 8x10 with
    a 3MP camera. Going with 200dpi as a minimum for printing, you are
    already at 8x10 (2048x1536 = 10.24" x 7.68"). This means that any
    cropping you might do will reduce the available pixels per inch for
    printing.

    So... Use a good steady tripod on a quiet day to take your pictures.
    Then don't do any cropping. See how those prints look. If it's a lens
    quality issue then you may not be able to do anything about it.
     
    Andrew McDonald, Nov 23, 2003
    #13
  14. Don

    Mark Johnson Guest

    Yeah, but for the precapture, and other auto features, I wonder if
    while film would be far superior, in detail, you'd get cleaner, more
    balanced, sharper photos with the digicam? So if the film equivalent
    is still better, for 'keeper shots', not just for any old thing (thus
    the advantage of digital, you're not buying film; think of an inkjet
    printer where you never have to buy ink), you'd have to get a good
    photo to begin with. Maybe it's easier to get that with the digicam.

    I would think, that since the 4MP is almost obsolete, at this point,
    and was only introduced maybe over a year ago, that the 10+ you see on
    the unaffordable Canon 1DS might work down to a good 'price break', in
    what - two years? Then you'd have the best of both. Of course, the
    rest of the firmware, and lenses, and maybe options, would also have
    to be a match of Canon. And the tendency to commodity doesn't always
    retain some of the best features of the leading edge. That's always
    the unfortunate part. But . . still.
     
    Mark Johnson, Nov 24, 2003
    #14
  15. Don

    Andy Hewitt Guest

    You're confuding the two resolutions above. One is total pixels, the
    other is pixels per inch. The 2048x1764 is also at 72dpi, to make this
    into 4800x1200dpi it needs to be enlarged to 136533x117588in order to
    keep the same resolution. Of course this would be ridiculous, and you'd
    never find a camera, or computer that could handle this.

    To make a working resolution you need to divide the stated dpi by the
    number of heads, I guess you have four colours, so your maximum
    resolution is in fact 1200x300. As a rule, you generally work at 300x300
    dpi for photos, even 150dpi would be sufficient on a decent printer.

    To be entirely honest though, I'd say you should be looking more to the
    printer. I have a Z53, and it cannot begin to come near the old Epson
    580 I had, which had a much lower stated resolution.
     
    Andy Hewitt, Nov 24, 2003
    #15
  16. Don

    jam Guest

    Don,

    | I just purchased a Minolta Dimage Z1. I only had it for a day, it's
    | my first digital camera and I know nothing about photography, but
    I'm
    | already creating great pictures with it.

    Welcome to digital.

    To all the good replies you've received, I'd only emphasize that you
    have to approach quality with the =entire= digital imaging chain in
    mind:

    lighting > filters > auxiliary lenses > camera > camera settings >
    photographer > post-processing > printer > paper

    Significant quality hits can arise at every link in the
    chain--particularly at the right end, after the camera. A bad paper
    choice for your printer can ruin an otherwise good picture. Crummy
    printers abound....

    I won't go into further detail, and I don't mean to discourage you,
    but you've just seen that you now have a lot of ways to screw up, and
    a lot of research and testing to do to get your setup optimized. This
    group is a great place to start (old posts are archived at
    google.groups.com--a treasure trove), and there are many other
    valuable photography resources online, not to mention in print, but...

    o Shoot more than your read.

    o Experiment like crazy. The marginal cost of another shot is now
    $0.00.

    o Get yourself a convenient, fast-loading image viewer that readily
    displays the exposure data embedded in every image file. Use it to
    examine every image that comes off your camera--especially the dogs
    and the masterpieces. After 4 years, I still like PIE shareware at
    www.picmeta.com for this purpose, but there are many good
    alternatives.

    o Have fun.

    Good luck.
     
    jam, Nov 24, 2003
    #16
  17. Andy Hewitt wrote:

    1x zoom is closer to 105mm in the 35mm standard.

    What you are talking about is this:
    A photo taken with a 49mm lens (35mm standard) when held at a distance
    away from your eyes equal to the diagonal length of the photo will look
    about the size as the view when you were standing there getting ready to
    take the picture.

    BCA
     
    Brian C. Allen, Nov 24, 2003
    #17
  18. Don

    Ron Hunter Guest

    Well, the camera has a few less photoreceptors than your eyes, and
    VASTLY less processing power working on the image provided by that
    photoreceptor.
    What you SEE is the result of some amazing massively parallel processing
    done by your brain.
     
    Ron Hunter, Nov 24, 2003
    #18
  19. 105mm? Where do you get this? 50mm is considered the "standard" focal
    length on a 35mm camera.
     
    Andrew McDonald, Nov 24, 2003
    #19
  20. Don

    Don Guest

    Following suggestions in the manual, I took the picture with the
    camera on a tripod as well as using the timer delay so my hands would
    not be touching the camera at the moment the shot was taken.
     
    Don, Nov 24, 2003
    #20
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