Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-20-2010, 07:50 AM   #1
Forum Member




Join Date: Sep 2009
Location: Houston, TX
Posts: 78
DC vs SDM?

I saw from a quick blurb about the new announced 18-135 WR lens and how it uses a DC (direct current) motor for autofocus. The DC is part of the lens name.

How is this different from SDM, or is it exactly SDM? The 17-70, and DA* have SDM in the lens name. Why not just have SDM in the lens name? Or is it to differentiate between DA* (fast lens+WR+SDM) lenses and consumer (slower) lenses ?

09-20-2010, 08:06 AM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,030
From my understanding, the DC motor is a type of motor used for the SDM system. Doubt it stands for direct current, though.

Perhaps it's faster!

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

09-20-2010, 08:27 AM   #3
Veteran Member




Join Date: Sep 2007
Location: La Crescenta, CA
Posts: 7,452
It does stand for Direct Current, per the official Pentax page for it.
09-20-2010, 09:01 AM   #4
REM
Forum Member




Join Date: Sep 2009
Location: Houston, TX
Posts: 78
Original Poster
Yes, it says Direct Current on the spec page for the lens on pentaximaging.com. just the thing to find out later is:

Is DC just a marketing term? (DC is same SDM technology, just used to separate DA* from DA WR lenses with SDM).

or is DC a new/different/updated SDM technology(SDM 2.0)?

Given the current state of SDM, I hope it is more reliable first, faster speed an extra perk!

09-20-2010, 12:27 PM   #5
Veteran Member




Join Date: Jun 2007
Location: Owego, NY
Posts: 976
To me, a DC motor implies a brushless DC micromotor, not an ultrasonic ring motor like found in higher-end in-lens focusing systems.
09-20-2010, 02:08 PM   #6
Veteran Member
womble's Avatar

Join Date: Apr 2010
Location: Hertfordshire
Photos: Gallery
Posts: 1,325
Here is the patent application for the new motor: ROTARY ACTUATOR
09-20-2010, 02:43 PM   #7
Pentaxian
Aegon's Avatar

Join Date: Jan 2008
Location: Portland, OR
Posts: 1,413
QuoteOriginally posted by womble Quote
Here is the patent application for the new motor: ROTARY ACTUATOR
Thanks womble.

QuoteOriginally posted by the Patent Application:
According to the present invention, a rotary actuator is achieved, in which torque in the circumferential direction is produced by magnetic force between the coil body and the multi-polar magnet by controlling currents supplied to the coil body. Accordingly, a reduction gear device becomes unnecessary, and miniaturization and a weight reduction of the actuator become possible. In addition, a high-voltage circuit for driving a motor such as an ultrasonic motor becomes unnecessary. Therefore, in the case where a rotary actuator according to the present invention is used as a drive source for an AF mechanism of a photographic lens, miniaturization of the AF mechanism becomes possible, so that miniaturization and a weight reduction of the photographic lens can be achieved.
So the new motor has more torque so it doesn't need a gearbox. And it can operate at lower voltages so it requires fewer electronic parts.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
da*, dc, k-mount, lens, lenses, name, pentax lens, sdm, slr lens, wr
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
645D, K-m2 and NEW LENSES DA*10-16/4 SDM, DA*20/2 SDM, DA*28/2 SDM ogl Pentax News and Rumors 165 08-11-2010 03:26 AM
DA 17-70mm SDM vs DA* 16-50mm SDM? shang Pentax SLR Lens Discussion 4 07-02-2010 06:09 AM
New 55mm SDM 645D lens means no SDM II? alehel Pentax News and Rumors 11 03-14-2010 09:43 AM
New SDM rear TC, SDM only or SDM + screw drive? morfic Pentax SLR Lens Discussion 1 10-01-2008 08:23 AM
Lens offer from Amazon: DA* 50-135 SDM & DA* 16-50 SDM f8 Pentax SLR Lens Discussion 4 03-25-2008 04:45 AM



All times are GMT -7. The time now is 09:31 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top