Sigma and Tamron 18-200 for Pentax

Discussion in 'Pentax' started by Charlie Self, Jul 18, 2007.

  1. Charlie Self

    Charlie Self Guest

    I'm curious as to which of these is supposedly the best. Are the tests
    or opinions I've missed (probably many)?

    I'm not enamored of the f/6.3, but otherwise they seem decent, with
    the Sigma having a pretty good price edge.
    Charlie Self, Jul 18, 2007
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  2. Charlie Self

    Roger Guest

    I've had the Sigma for about 1 1/2 years now and have been happy with it.
    It's small, light, and has excellent zoom range.
    I've done some comparisons with my 17-40 F4L and have been absolutely
    amazed - as long as you stop it down. It is definitely not a fast lense
    but if you have enough light to get to f/8 or so, it actually does very
    very well. Mind you, barrel distortion at less than about 22mm gets pretty
    significant but nothing DXo can't repair. I cannot comment on the Tamron.
    Roger, Jul 18, 2007
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  3. When I was choosing between them two years ago for a 300D I went with
    the Sigma. Main reasons were I didn't like the play in the Tamron's
    barrel when it was extended and I thought the Sigma's image quality was
    a little more to my taste. I suggest you look hard at the Tamron
    18-250mm. It appears to be better than either of the 18-200mm lenses.
    It is a new lens from Tamron. Here's a link:
    Michael Johnson, Jul 18, 2007
  4. Charlie Self

    Pete D Guest

    Have a look at the tests on you may be better going for
    the Tamron 18-250.
    Pete D, Jul 18, 2007
  5. Charlie Self

    babaloo Guest

    I have had the Sigma for about two years and more recently the Nikon 18-200
    Optically there is not much to distinguish one lens from the other. In fact
    in my side by side comparisons the Sigma seems to have less barrel
    distortion at the wide end while the Nikon does not vignette as much wide
    open at 18mm. Barrel distortion, if it bothers you, is easily
    corrected/minimized in an image processor. Both the Sigma and Nikon have far
    less chromatic aberration, which is often not correctable, than the average
    18-50 class kit zooms that I have seen.
    All these 18-200 lenses are great for travelling. The Sigma, bereft of image
    stabilization, is much lighter to carry around than the Nikon. As a class
    they are, in my experience comparing them to the execrable Nikon 55-200,
    optically superior to that 55-200 lens through that part of their zoom
    Obviously glass of this zoom range will not have ideal performance at all
    focal lengths/apertures. These are not Leica single focal length hand
    crafted range finder lenses. But for what they are the 18-200s on a dSLR are
    very good values.
    I have trekked through Asia and Europe with the Sigma: I have no complaints
    about it. The barrel locking tab, so the zoom does not extend while you are
    walking with the camera dangling from your neck, is a very convenient touch.
    The only reason I got the Nikon was that I just can't hold the camera as
    steady as I used to. With the Pentax dSLRs optical stabilization is already
    wisely built into the camera.
    babaloo, Jul 18, 2007
  6. Charlie Self

    Bengt C Guest

    I recently bought an XTi and imediatelly discovered how poor the kit
    lens is. Coming from Fuji F10 compact, I certainly expect improvement
    in every aspect except price and weight. In particular I think you
    should be able to use apertures larger than F/8. Not so with a Canon.
    (First bought Olympus E-410; Very good kit-lens, unfortunately useless
    in low light though.)

    According to and Sigma 18-200 has soft
    borders at ~35 mm. Unfortunatelly that is a very useful focal length
    and I would be suspicious about that lens for this reason. I instead
    just bought Sigma 18-125 the other day because it doesn't have this
    weakness. I tested it on tripod for several hours in the shop and
    compared it against a few other lenses. I tested at 18 mm and 50 mm
    and only large appertures F/4 and F/5.6 (All lenses are good at F/8
    which is why lens tests at are entirely useless.)

    * Sigma 18-125 has much better resolution and contrast than the Canon
    kit lens at all appertures, not only in the borders but everywhere.

    * Sigma 18-125 has better contrast and slightly better resolution
    than Canon EF-S 17-85.

    * Sigma 18-125 has slightly lower cromatic aberation than Canon 17-18
    and the kit lens. Cromatic aberation is more red than purple though.

    * Canon 17-85 did not focus more reliably in dark conditions under a
    table. It "hunted" faster, with less sound, but it did not pick focus
    more reliably. It missed just as often as the Sigma. (No assist light)

    * Canon 17-85 has image stabilisation which of cource is very useful
    indoors (evident without tripod in the shop). But it's also 100 g
    heavier, *much* larger and almost $600 more expensive, in my case.
    (Half of that money buys a big flash should 1600 ASA not suffice.)

    I bought the Sigma 18-125 as it's disappearing from the market at this
    very moment. I I got a good deal on the shop's demo which was the one
    I tested and thus the one I wanted to buy. I think the 18-200 range is
    more of a compromise and I also doubt 200 mm is useful without image
    stabilisation. (I have no interes carrying tripod nor fiddle with it)
    Only strange thing is 18-200 gets higher user reviews than 18-125,
    despit it should (clearly?) be the other way around. Strange?

    After buy, I took it to a tower and did a long range test (shooting
    over a city) Again it outperformed the kit lens everywhere, *except*
    at the right border, 18mm and large appertures. I have to investigate
    that a little further though. Conditions were not 100% controlled.
    Sun came and went and I didn't use the hood. Perhaps my breath caused
    something. (Unlikelly?) I'm not sure where the focus was. I don't know
    if it foucused at infinity or only perhaps 15 m in front of the cam.
    The kit-lens rendered a part of the tower at 10m more blurry than the
    Sigma. But FWIW, I didn't see any problems in the middle or left part
    of the picture.

    Anyway, good luck with your choice. Rest assure all lenses are better
    than the Canon kit lens. I think even a Sigma 18-50 F/3.5-5.6 should
    be sharper at large appertures (and almost as light weight).
    Bengt C, Jul 20, 2007
  7. Charlie Self

    Mark B. Guest

    Nobody else mentioned this, but take a look at the new version of the Sigma
    which is optically stabilized. Assuming the IQ is no worse, and hopefully
    better, it would make the f/6.3 easier to use.

    Mark B., Jul 20, 2007
  8. Charlie Self

    gerrit Guest

    Why would the OP use an image stabilised lens since it will be used on
    Pentax body which already has IS built in?

    gerrit, Jul 21, 2007
  9. Charlie Self

    Sander Guest

    Doesn't matter. None of the optically stabilised lenses are available in
    Pentax mount anyway.

    Sander, Jul 21, 2007
  10. Charlie Self

    Mark B. Guest

    Ok, you're right, I missed that.

    Mark B., Jul 22, 2007
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