Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-11-2007, 07:21 AM   #1
Veteran Member




Join Date: Mar 2007
Location: Munfordville, Ky.
Photos: Gallery
Posts: 370
Sigma 17-70 2.8-4.5 lens

I've been taking some sample shots with a recently purchases Sigma 17-70 lens. I've noticed that I'm unable to obtain a wider aperature than 3.5 despite the fact that the lens is supposed to open up to 2.8. Any suggestions other than sending the lens back to the seller or to Sigma? Thanks.

05-11-2007, 08:39 AM   #2
Site Supporter
pschlute's Avatar

Join Date: Mar 2007
Location: Surrey, UK
Photos: Gallery
Posts: 702
Apologies if you know this already, but i think you will find that f2.8 is only possible at 17mm zoom. As you zoom in the minimum aperture will get slower.
05-11-2007, 09:38 AM   #3
Veteran Member




Join Date: Dec 2006
Location: Outside of Philly
Posts: 1,564
That's why it's called the "Sigma 17-70mm f/2.8-4.5", note the "f/2.8-4.5" part At 17mm, you can open up to f/2.8, but at 70mm, the maximum aperture is f/4.5

If you want f/2.8 throughout the entire zoom range, you need to buy the Sigma 18-50mm f/2.8 and/or the Sigma/Tamron 24/28-70/75mm f/2.8...
05-11-2007, 11:40 AM   #4
Veteran Member




Join Date: Mar 2007
Location: Munfordville, Ky.
Photos: Gallery
Posts: 370
Original Poster
Max aperature of 3.5 at 17mm

I'm aware of the fact that I'm only supposed to get 2.8 at 17mm. The problem is that the camera will only show a maximum aperature of 3.5 at 17 mm. (At 70mm I get 4.5 just as I'm supposed to.) I don't have any faster lenses to put on my K10D, so I'm wondering if the problem is with the lens or with the aperature indicator on my camera???


Last edited by Clem Nichols; 05-11-2007 at 11:43 AM. Reason: Additional info
05-11-2007, 01:00 PM   #5
Senior Member




Join Date: Mar 2007
Location: Ålesund, Norway
Photos: Gallery
Posts: 170
Sounds like a problem with your lens.
05-13-2007, 06:06 AM   #6
Inactive Account




Join Date: Mar 2007
Location: Long Island, N.Y.
Photos: Gallery
Posts: 1,124
Make sure you're not in the MTF mode. I just checked my 17-70 which I have set in P & MTF and the max aperture shows as F4.0. I can turn the dial to get 2.8, or if I put it back in straight P mode it goes to 2.8 fine.
Brian
05-13-2007, 11:04 AM   #7
Veteran Member




Join Date: Mar 2007
Location: Munfordville, Ky.
Photos: Gallery
Posts: 370
Original Poster
No luck! Nothing seems to work. There seems to be nothing mechanically wrong with the aperature blades in the lens, as they open fully to 4.5 at f70. It's too bad there's no one close with another Pentax camera I could check the lens on or a faster lens I could check on my camera. That should certainly tell me if the problem is with the lens or the aperature indicator on my K10D.
05-13-2007, 11:43 AM   #8
Inactive Account




Join Date: Mar 2007
Location: Norfolk , Va.
Photos: Gallery
Posts: 133
If there is a camera store near you that deals in Pentax cameras you may be able to check your camera with another lens they carry in stock or try your lens on a store camera.
I hope you get the problem figured out soon.Best of luck .
Kenn

05-13-2007, 12:45 PM   #9
Site Supporter
slip's Avatar

Join Date: Oct 2006
Location: 2 hours north of toronto ontario canada
Photos: Gallery | Albums
Posts: 3,515
this sounds to simple and you might have already tried it but take the lens off and put it back on. my camera was acting weird with my sigma flash one day and I did this and it seemed to clear up the problem.

randy
05-13-2007, 02:45 PM   #10
Veteran Member




Join Date: Mar 2007
Location: Munfordville, Ky.
Photos: Gallery
Posts: 370
Original Poster
Already tried removing and replacing the lens to no avail. Thanks anyway.
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!
k-mount, lens, pentax lens, sigma, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: [US] Sigma EF-530 DG ST flash, AF Sigma 28-200mm f3.5-5.6 lens rockmaster1964 Sold Items 2 02-24-2010 10:07 AM
For Sale - Sold: Pentax Lens Blowout; 50mm 1.4, Sigma 10-20mm, Sigma 400mm, etc. nufenstein Sold Items 13 03-30-2009 12:00 PM
Sigma lens, OneStop Digital customer service, Sigma again vytas Pentax SLR Lens Discussion 3 10-30-2008 03:23 PM



All times are GMT -7. The time now is 03:30 AM. | See also: NikonForums.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