New Sigma HSM ONLY tele zooms for Pentax

Discussion in 'Pentax' started by renatoa, Feb 12, 2008.

  1. I emphasize once again HSM ONLY :( AF will not work on bodies with AF via
    embeded motor ...

    http://www.photographyblog.com/index.php/weblog/comments/sigma_50_150mm_and_70_2
    00mm_lenses_for_sony_and_pentax/
     
  2. I don't think this is a :( at all. It's a sensible move on Sigma's part since it means they can make the lenses mechanically the same as those for other mounts with support for in-lens motors.
     
  3. The complete link.

    I have to agree with Matthew; if you own a digital Pentax from the last year you have no problems whatsoever. It makes complete business sense for Sigma to do this as they need the HSM to stay competitive, and the other option may have been to simply not have Pentax mount versions at all. Of course, those people with non-Super K100D's and *ist's won't be able to benefit from these new lenses, but I'm sure Sigma expects most of these users will upgrade their camera within a year or two.
     
  4. Personally, I haven't used any HSM lenses but I doubt I would upgrade my camera just because two lenses came out. Pentax is known to be backwards compatible so Sigma's move does not impress me at all.
     
  5. I just sold the Sigma 50-150 f/2.8 and a Tamron 17-50 f/2.8 with my Canon EOS gear and put the money toward my K10D and DA* and limited lenses.

    I have nothing but praise for this Sigma lens it's one of the sharpest and highest quality zooms I've ever used. It holds it's own nicely against some of Canon's finest namely the 70-200 L's. Were it shipping right now I'd buy another one, but I'm ordering the DA*50-135 this week as I have to have the range covered before the Sigma will ship. And has been mentioned the DA* will work on my K100d too.

    I think Sigma did the right thing here. The lens uses a ring style ultrasonic motor. And I can tell you it focused faster and smoother on my Canon than the DA*16-50 does on my K10d which apparently uses a micro ultra sonic motor to drive the screw shaft rather than a ring type ultrasonic motor. In real world shooting they will both get the job done; the ring style is a bit faster. I think Pentax has made a sight focusing speed compromise to maintain backward compatibility and keep the screw drive focus mechanism.

    Making the Sigma compatible with a screw drive would likely have require a significant redesign of the lens. Where as making it HSM only should have been a matter of adapting the connections and electronics. They did the right thing having available in Pentax is an asset. It's a GREAT lens.
     
  6. If Pentax can do it, so could Sigma- that is make lenses compatible with both body styles, having the SDM version of HSM. This is especially limiting with their full frame 70-200mm f/2.8 because Pentax has never made a FF film camera with SDM. So for me, the new Tamron $700 70-200mm is the attraction. But at least Sigma did finally make some pro style lenses with the HSM available for Pentax. Maybe too much of a redesign to make them all around compatible.

    And just when Pentax is dropping the K100D Super!!
     
  7. " And I can tell you it focused faster and smoother on my Canon than the DA*16-50 does on my K10d which apparently uses a micro ultra sonic motor to drive the screw shaft rather than a ring type ultrasonic motor."

    My goodness. If Pentax is putting micro USM in its lenses this is sad indeed. Micro USM is a complete waste of time. Ring USM is where it is at.
     
  8. mountainvisions

    mountainvisions Moderator

    Geoff,

    I might be wrong but I think Canon uses both!!!

    At least I've read that.

    There are advantages to both.
     
  9. mountainvisions

    mountainvisions Moderator

    Whats interesting about the text below is that it states Ring Type allows for spot manual focusing but micro doesn't. Interestingly, Pentax if it is using "micro motor" is using an improved version because holding my 50-135 in AF mode, I'm surely manual focusing without changing a setting. And I'm not worried about breaking a thing because right in the book it says to do so.

    Also, the "noisy" gear train isn't quite fitting to a T. That is it's near perfectly silent. But on my ist D it sure as heck makes noise.

    I'm thinking Pentax micro USM is a bit different than the one Canon came out with in the early 1990s. With 18 years to work on it, I'd hope so!

    In hind sight backwards compatibility for DA lenses does seem pointless as digital bodies come and go, but lets say they went full frame, I'm certain a few of those DFA SDM lenses would find their way onto film bodies like the PZ-1P, or ist 35mm or any other camera with body controllable aperture.

    That said, for shooting action I'd probably lean more to the Sigma with the faster Ring type for the same money. Choices are never simple are they?


    ------

    From DP Review:

    http://forums.dpreview.com/forums/read.asp?forum=1029&message=15260787

    The original and best USM, known as a "ring type USM", was introduced by Canon in the early 1990's. This type doesn't even look like a motor and instead appears to be nothing more than two large rings with a few wires poking out of them. One ring is connected to the focusing parts of the lens and the other to the barrel, and when one part is made to vibrate at ultrasonic frequencies (hence the name) this translates into rotational movement of the other. This type is fast, almost completely silent (except to dogs and bats!) and there is no need for a gear train or other noisy mechanicals. Ring USM also has another advantage - full-time manual focussing or FTM in which, once auto-focus has completed, the lens focus can be "touched up" using the manual focus ring without having to switch the lens from AF to MF. Canon uses ring type USMs on nearly all its mid-range and L-series lenses except for a few very early designs which were introduced before USM was invented.
    Ring type USMs:

    The other (and lesser) type USM is known as a "micro-USM". This is a form of USM motor that Canon designed for their less expensive lenses so they can bill them as "ultrasonic" - essentially for marketing purposes and to cash in on the reputation of the ring-USM. These little motors operate on the USM principle but still use a noisy mechanical gear train and so are really no different or better than their cheaper micro-motor alternative. They also (except for the 50/1.4 and 28-105/4-5.6) lack FTM focussing and have a fairly poor record reliability-wise.
     

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