Sigma - difference between DG and older lenses

Discussion in 'Digital SLR' started by Belgos, Apr 5, 2006.

  1. Belgos

    Belgos Guest

    Hi all

    Regarding the sigma 70-300 apo macro, what is the difference between the
    older one made for 35mm and the new 'DG' one ? Is the fov for both changed
    to the equivalent of x1.6 on dslrs ? Can the DG be used on a 35mm, and can
    an older non-DG model fit the rebel xt?

    Also, do extension tubes work the same way (regarding macro reproduction
    ratio) when used on a dslr ? I hope I am not too mixed up.

    Thanks in advance
    Kostas
     
    Belgos, Apr 5, 2006
    #1
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  2. Belgos

    John Bean Guest

    Sigma suffixes are confusing.

    "DG" simply means it's been "optimised" for digital use -
    probably just lens coatings - but otherwise it's
    functionally the same as the non-DG lens and it covers full
    frame as well as smaller sensors, or 35mm film.

    "DC" means it can only be used with APS-C sized sensors (or
    smaller) and the image circle is too small to cover a
    full-frame sensor (or 35mm film).
     
    John Bean, Apr 5, 2006
    #2
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  3. DG means improved coatings. I am not able to tell the difference,
    but some people claims that DG is less prone to ghosting.
    No. The focal width remains unchanged.
    Yes. All Sigma's DG lenses are FF.

    Sigma uses the tag DC to designated smaller image circles, but a
    Sigma DC will physically fit on a film camera (but will vignette),
    while a Canon EF-S will not.
    Yes. The reproduction ratio (1:1) tells you that 1 millimeter in
    "real life" will measure 1 millimeter on the film/sensor. That
    doesn't change even if the sensor becomes smaller. Of course, if you
    were to photograph a ruler at 1:1, you would capture 36 mm of it on
    film, but only 22.5 mm with a Rebel XT.
     
    Gisle Hannemyr, Apr 5, 2006
    #3
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