Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
07-23-2013, 09:52 AM   #1
New Member

Join Date: Sep 2012
Photos: Albums
Posts: 23
Question about focus lock indicator on manual focus lens

Hey everyone, I've been shooting with my K-r for some time now and I've found the auto-focus to be pretty good most of the time with AF lenses. But I've been seeing some strange behavior (to me anyway) when using my SMC Pentax-A 50mm F1.7 which is a manual focus lens.

Firstly it seems that in lower light the camera will do a good job with an auto focus lens and will focus for me, but with the manual focus lens it often will not give me a focus lock indicator at all in the same low light, or it will be way out to lunch.

Secondly, in good light it seems that the focus lock indicator is often way off. If I'm shooting anything where I have to get the shot right the first time then I can't go anywhere near the fast side of this lens or I'm guaranteed to have a focus problem even if I get focus confirmation from the camera. To make things more interesting, the camera will indicate focus lock at a little different position depending on which direction I'm turning the MF ring. This lens is SHARP and the results are spectacular if I happen to nail the focus, but the indicator in the camera only seems useful to get me in the ballpark (which I could have done by eye anyway), and then it's a pure numbers game firing off enough shots in multiple setups hoping that one of the setups will yield a proper focal point.

I've done a few events, will be shooting my first wedding this weekend, and am getting enquiries for another wedding. Wondering if it might be time to step up to a K5ii with a better AF system...

One more comment, when I fire up the camera with the 50mm prime on the body it asks for the focal length. Should I be telling it that it's 50mm or 75mm? (APS-C equivalent with a FF lens on a smaller sensor). I've experimented with both settings but it doesn't seem to make any noticeable difference.

Thanks in advance for any advice.

07-23-2013, 06:01 PM   #2
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 49,830
Af confirmation with manual lenses has a fairly big tolerance, so I'd recommend stopping the lens down to make up for it with the dof.

You should be setting the fl to 50mm.

Adam Webmaster (Site Usage Guide | Site Help | My Photography) server and development costs are user-supported. You can help cover these costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

07-23-2013, 11:18 PM   #3
New Member

Join Date: Sep 2012
Photos: Albums
Posts: 23
Original Poster
Thanks for the reply Adam, confirms some things for me. I wonder if I might get more consistent results with an AF 50mm prime, letting the AF do it's job then recomposing the shot. The AF / MF switch probably wouldn't like that treatment though.
07-23-2013, 11:42 PM   #4
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 10,928
QuoteOriginally posted by jostafew Quote
To make things more interesting, the camera will indicate focus lock at a little different position depending on which direction I'm turning the MF ring.
With a bit of practice, you can hit the middle of the indicated "acceptable" range.
I often go back and forth with the focus, exploring the end points of the "acceptable" range and then try to hit the middle point. This often works well for me.

I'm not sure whether your K-r supports "catch in focus" but this once worked well for me. Another time, with another lens, it didn't but I haven't tried to get to the bottom of this.

Finally, if feasible, using a high magnification factor in live view can yield excellent results.

07-24-2013, 05:16 AM   #5
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,365
I also have the K-A 50, f/1.7 lens. Frankly, 90% of the time I ignore the focus indicator and just use my own eyes; and then I select an aperture at least a couple stops down from wide open.
07-24-2013, 09:30 AM   #6
New Member

Join Date: Sep 2012
Photos: Albums
Posts: 23
Original Poster
All good advice, thanks everyone.
07-24-2013, 10:50 AM   #7
Junior Member

Join Date: Aug 2010
Posts: 36
QuoteOriginally posted by jostafew Quote
All good advice, thanks everyone.
i have the same issue. same lens same k-r. i use live view and the focus locks perfectly.

  • 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!
50mm, camera, focus, indicator, k-r, kr, lens, light, pentax k-r, time, wedding
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Focus Indicator Accuracy With Old Manual Lens Siegfried Pentax K-5 24 04-28-2012 06:37 PM
Question of focus with a manual lens on a K-01 visual zen Pentax K-01 3 02-18-2012 10:27 AM
Question about manual focus on 18-55 kit lens Matso Pentax K-r 6 03-09-2011 12:15 PM
Question about using manual focus lens. XMACHINA Photographic Technique 3 02-13-2008 08:23 AM
Focus Lock/Recompose with Manual Lens Panache Pentax DSLR Discussion 15 05-15-2007 03:32 PM

All times are GMT -7. The time now is 09:17 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]