Film camera and lens questions

Discussion in 'Beyond the Basics' started by drlynn, Sep 30, 2003.

  1. drlynn

    drlynn TPF Noob!

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    "mm" means millimeters, and is a measure of the focal length of a lens. Your example of a 28-90mm lens is one that zooms from a wide angle of 28mm out to a telephoto 90mm. The term "f/4-5.6" refers to the maximum aperture of the lens. In this case, this lens can open up to f/4 at 28mm, and to f/5.6 at 90mm.

    The lower the f-stop number, the wider the lnes can open, and therefore the more light that can strike the film. f/4 is wider than f/5.6, and so you can use faster shutter speeds.

    There are many web sites that talk about camera basics. The only one I can think of off the top of my head is Silverlight Photography Tutorials,

    http://www.silverlight.co.uk/tutorials/toc.html

    Hope this helps. :D
     
  2. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    The profusion of mm measurments can be confusing. "I need a 49mm filter for a 50mm lens on my 35mm camera." The camera uses 35mm film. The lens has a focal length of 50mm (or a range of focal lengths in a zoom such as 28mm-200mm) and a diameter of 49mm (for attaching accessories such as filters and lens hoods).
     
  3. lukeybaby

    lukeybaby TPF Noob!

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    what is the difference between apeture when you are taking pics, to apeture of the lens?? because my pentax sf-7 35mm lens has an apeture of like f2.8-22 when i am taking photos.

    what do you exactly mean by "wide angle" and telephoto" ???

    sorry about so many Q's, i really wanna learn as much as i can about manual SLR's.

    luke z
     
  4. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Aperture (or f/#) refers to the size of the hole allowing light through the lens. Not that you need to know it but focal length divided by f/# equals aperture. Almost all lenses have a range of f/#s (like f/2.8 through f/22 on your 35mm lens), but a lens is known by it's widest aperture (so that lens is a 35mm f/2.8).

    On consumer zoom lenses the actual measure of the aperture stays the same even if you zoom out so the f/#changes (so using the formula above: an aperture of 10mm at a focal length of 40mm = f/4, and an aperture of 10mm at a focal length of 80mm = f/8). So on your 28-90mm f/4-5.6 zoom lens, when you are at a focal length of 28mm the widest aperture is f/4, but as you zoom out to 90mm you are changing the math, so at a focal length of 90mm your widest aperture is f/5.6. This same effect happens up and down the f/# scale (f/22 at 28mm becomes f/32 at 90mm).

    On "pro" zoom lenses the f/# stays the same, and the actual size of the aperture changes as you zoom.

    Are you confused yet? Most of the above really isn't that important as long as you understand how the f/# controls exposure and depth of field.

    A focal length of 50mm is considered "normal" because it renders an angle of view and perspective similar to the human eye. Focal lengths shorter than 50mm are "wide". Focal lengths longer than 50mm are "telephoto"(is this the right term, I think telephoto may actually refer to a lens design that has a perceived focal length longer than it's actual physical focal length?). Just look through your camera and play with the zoom lens for a demonstration.
     
  5. motcon

    motcon TPF Noob!

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  6. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    everywhere in the above post where you see smiley guy it's supposed to read f/two point eight
     
  7. motcon

    motcon TPF Noob!

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    lol.
     
  8. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Actually it looks like the first one is f/2.8

    and the second on is f/8

    I've been whacked by smiley guys!!
     
  9. lukeybaby

    lukeybaby TPF Noob!

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    thank you so much for your help. i understand that the smaller the apeture opens, the larger the f number will be, therefore it will let in less amount of light and your shutter speed will have to be slow(maybe 1/30) to increase the light being exposed to the film!???. the higher the f number the more depth of field, right?

    sorry!, what exactly is the focal length?? geeezee manual photography is so confusing, lol

    luke z
     
  10. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Focal length is the measure of the distance between the film plane and the optical center of the lens when focused at infinity. It's how we designate lens size; it's the mm measure you first asked about.

    Manual photography seems complicated at first, but it gets easier. You can't learn everything overnight, but as one concept is understood, you can move to the next.
     
  11. motcon

    motcon TPF Noob!

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    all you really need to grasp at the beginning is the trinity:

    shutter speed, aperture, film speed

    and how they relate. i'd start there.
     
  12. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    And when you can grasp the pebble from our hand, Grasshopper, then you will be ready to go.
     

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