Analoog <> Digital objective?

Discussion in 'Digital Cameras' started by JennyC, May 11, 2007.

  1. JennyC

    JennyC Guest


    I'm new here and have a question: Is there a difference between an analoog
    objective and a digital one?

    I had Canon 350E with a Tamron 28/200 objective.

    I treated myself to a Canon 350D (came with an 18/55 objective)

    I kept the 28/200, but does not have such a wide angle on the 350D as it
    did on the old camera.

    Any idea please??
    JennyC, May 11, 2007
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  2. JennyC

    Ed Ruf Guest

    Your 350D is NOT a full frame sensor. The sensor size is smaller than
    the 35mm film frame. So the image you see with it is a crop of a full
    film frame. So the field of view is smaller on the digital, by what is
    frequently called a crop factor. For the canon this is 1.6, so the
    field of view you see with the 18mm lens on the 350D is equivalent to
    what you would see on the 350E with a 18 x 1.6 ~ 29mm lens.
    Ed Ruf ()
    Ed Ruf, May 11, 2007
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  3. ("Lens" is the common English term for the optical element you mount on
    the front of a DSLR).

    And the answer is "not really". Mostly when manufacturers make lenses
    specific to their digital bodies (like Nikon's DX line of lenses and
    Canon's EF-S line), the primary difference is in the size of the image
    circle produced. These special lenses can't be used on full-frame film
    bodies (or full-frame digital bodies).

    (There seem to be some issues with wideangle lens design for some
    sensors, but they're not huge; also some issues with anti-reflection
    coating on the rear elements. Some manufacturers mention a lens as
    being "for digital" if it has had these issues carefully addressed, and
    they do make some difference.)
    Nearly all the DSLR bodies made today (except the Canon 5D and 1Ds) (and
    there were a couple of older ones, no longer made, like the Kodak
    DCS/14n) have a digital sensor smaller than the full 35mm film frame
    (smaller than 24mm x 36mm). The pictures you get from them are
    equivalent to cropping the center portion out of the full film image in
    the darkroom.

    The Canon consumer DSLRs have what's referred to as a 1.6x crop factor
    -- this means that the field of view you get with (for example) a 50mm
    lens on your 350D is the field of view you'd get with an 80mm lens on a
    full-frame 35mm camera. If you're familiar with what field of view to
    expect on a 35mm film camera, keeping this 1.6x factor in mind can ease
    the transition. If you're not, don't worry about it, and just learn
    what the lenses do on your camera.

    (To confuse things, Canon actually makes DSLRs with *three* sensor
    sizes; as mentioned the 5D and 1Ds have full-frame sensors, and the 350D
    and nearby models, up to the 30D, have 1.6x sensors. In addition to
    that, the 1DmkII (note the absence of an "s") has a 1.3x sensor.)
    David Dyer-Bennet, May 11, 2007
  4. JennyC

    JennyC Guest

    Thanks Ed and David,

    All is clear to me now.

    I think I shall be looking at a Tamron 18-250 XR Di II...............

    JennyC, May 11, 2007
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