Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
03-30-2013, 12:06 PM   #1
Senior Member

Join Date: Nov 2011
Posts: 120
K5IIs and Sigma 30mm focus issues

Been using the Siggy for a week or so now and not really checked for any focus problems until today.

I took some shots using the far left and far right focus points. At f1.4 the camera confirmed focus but nothing was in focus at all. the whole pics came out as a blur. It got slightly better starting at f2.8, but not great.

Once you move in to the next left and right focus points in, the problem goes.

I tried out the 18-135 and this shows no such issues.

Is this common with primes or Sigma lenses?

Just a quick edit... if I use MF i can get what i want in focus on both the left and right focus points.

I tried fine tuning the AF to both -5 and -10 and +5 and +10 and it did not make a lot of difference if any.

Edit again... was using far left focus point and item in frame on front right was in focus! Think I have issues with this lens!!

Last edited by JayX2A; 03-30-2013 at 12:56 PM.
03-30-2013, 01:03 PM   #2
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
with fast lenses the field of focus is often quite curved, so the focus across the frame wide open can be all over the place. also these lenses aren't very much corrected ate the edges so the focus can easily be fooled.

and also... the edge focus points aren't that accurate to begin with.
03-30-2013, 01:19 PM   #3
Senior Member

Join Date: Nov 2011
Posts: 120
Original Poster
Ahh thanks for the reply. I'm going to to a focus chart test just to check its not back/front focussing.
03-30-2013, 02:20 PM   #4
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
fast lenses can be problematic though, good luck. I returned my first 30mm when I bought it. I could not get it to focus right. second one was almost perfect out of the box. you need to get a bit lucky.

03-30-2013, 02:25 PM   #5
Senior Member

Join Date: Nov 2011
Posts: 120
Original Poster
Seems to be focussing ok in most occassions bar the far left and right points. I'm not sure how often I would be using them with this lens anyway! Apart from that the IQ seems very good. Maybe its just as you mentioned, the curved view and the fact the sigma is meant to be quite soft at the edges.

Not sure whether to try another copy or not. It might just be how this lens behaves TBH, I doubt many people have tried the left and right focus points with it!
03-30-2013, 02:54 PM   #6
Senior Member

Join Date: Jun 2012
Photos: Gallery
Posts: 218
Where did you buy it? Did you buy it at a good price? I'm still looking for this lens.
03-31-2013, 06:20 AM   #7
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
All of these fast lenses have soft corners and a curved field,it's the nature of the beast.

If you can get the center focus to shift infront and back the subject with -10 and +10 focus adjustment it mens you can adjust the lens.
My first sigma needed over -10 so i could not get it right on my camera.

Both the lens and camera have a small error so if my camera has -5 error and the sigma lens -7 the effect would result in -12 so out of the range of adjustment.
Someone else with +7 camera would be very happy with that lens.

These numbers are actually measurements of 10 μm (0.000001 of a meter) just to show how small these errors actually are.
04-02-2013, 01:38 AM   #8
Senior Member

Join Date: Nov 2011
Posts: 120
Original Poster
Camera is not back or front focussing in the centre from what I can see. I'm thinking it may be the nature of the lens as mentioned that the far left and right focus points send it in to meltdown!

Can anyone test theirs to see if it does the same?


  • 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!
camera, dslr, focus, issues, k-5, k-5 ii, k-5 iis, k5, pentax k-5, sigma
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Anyone have the k5iis and the sigma 15 - 30mm ex dg combo? slip Pentax K-5 0 12-05-2012 05:39 PM
Question about Focus on a used Sigma 30mm 1.4 tanporakuda Pentax SLR Lens Discussion 9 10-19-2012 11:25 AM
Focus/shot and exposure issues Homey16 Troubleshooting and Beginner Help 2 01-24-2012 10:52 AM
Sigma Zoom Focus Issues dadipentak Pentax SLR Lens Discussion 2 10-06-2011 04:18 AM
Sigma 70-200 focus issues, worth sending to Sigma? nobbsie Pentax SLR Lens Discussion 4 11-17-2008 03:06 PM

All times are GMT -7. The time now is 08:28 PM. | 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]