Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
10-11-2010, 05:14 AM   #1
Veteran Member
bc_the_path's Avatar

Join Date: Mar 2007
Location: Ankara, Turkey
Photos: Gallery
Posts: 390
Sigma 17-50mm f/2.8 EX DC with OS (~SDM)

As a former (happy) user of Sigma's versatile 17-70mm f/2.8-4.5 lens; I have just got the new offering with fixed maximum aperture today. I will report my experiences here soon (perhaps reviving this thread).
In the meantime, you can perhaps look at the two reviews about this new kid on the block (on different mounts):
1) Photozone:
Sigma AF 17-50mm f/2.8 HSM DC EX OS - Review / Test Report

2) Lenstip (a useful Polish site) :
Sigma 17-50 mm f/2.8 EX DC OS HSM review - Introduction -

A comparative analysis with Tamron 17-50mm f/2.8 would be nice (as the Pentax lens with the similar range is pricier than both). I believe the reported user experiences with the Tamron was very good.

My first impression is positive and the lens seems to be focusing normally (no front- or backfocus). More will follow

10-11-2010, 06:02 AM   #2
Veteran Member
pop4's Avatar

Join Date: Aug 2007
Location: YMML
Photos: Gallery
Posts: 1,877
Yay, another person with this lens. I posted a few of my initial thoughts about the lens here:
Hmm, I probably should update that
10-12-2010, 01:40 AM   #3
Veteran Member
bc_the_path's Avatar

Join Date: Mar 2007
Location: Ankara, Turkey
Photos: Gallery
Posts: 390
Original Poster

- There is no front- or back focus.
- The lens is internally focusing. The length changes only with the focal length.
- AF is fast. Really, very fast (and, naturally, quiet). This is due in part to the very short focus travel; about 30 degrees, perhaps. So, from 30cm to infinity the barrel takes not more than a 1/10th of a full turn.
- MF is possible but unlikely to be precise, see above.
- Optical stabilization (turning the SR off) is very good and probably a bit better than the in-body system. However I have not done any systematic testing. I already got the impression that OS may be consuming a bit more battery power than the SR. Time will tell.
- The barrel does move during AF but this is hardly a problem since the travel is usually a few millimeters only.
- Resolution and contrast are very good (again, without formal testing yet).

Last edited by bc_the_path; 10-14-2010 at 02:31 PM.

  • 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!
17-50mm, dc, f/2.8, f/2.8 ex dc, k-mount, lens, os, pentax lens, sigma, sigma 17-50mm f/2.8, slr lens, tamron
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Another SDM Failure - 16-50mm f/2.8 Donkeypunch Pentax SLR Lens Discussion 40 12-05-2011 05:09 PM
DA 17-70mm SDM vs DA* 16-50mm SDM? shang Pentax SLR Lens Discussion 4 07-02-2010 06:09 AM
D-FA 50mm f/1.0 SDM jaad75 Pentax News and Rumors 219 05-31-2009 04:21 PM
New SDM rear TC, SDM only or SDM + screw drive? morfic Pentax SLR Lens Discussion 1 10-01-2008 08:23 AM

All times are GMT -7. The time now is 11:57 AM. | See also:, 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?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]