Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-05-2017, 08:34 AM   #1
Junior Member




Join Date: Apr 2011
Location: Nashville
Posts: 38
SMC Pentax DA50mm f 1.8 - Auto focus hunting issue

Just had my new lens, Pentax SMC DA 50mm f1.8 delivered. I tried it on my K-5 and noticed that the lens is struggling to autofocus and it keeps hunting. Tried in Auto, Av, P and Sv. The manual focus seems to be working.

I tried an 18-135mm WR lens to eliminate that it's not the camera body and I was able to take pictures without autofocus issues. So I am sure the camera body is working.

Any help would be much appreciated. I want to make sure it's faulty before returning.

10-05-2017, 10:31 AM   #2
Forum Member




Join Date: Apr 2015
Location: Normandy
Photos: Gallery | Albums
Posts: 59
QuoteOriginally posted by iamarunr Quote
Just had my new lens, Pentax SMC DA 50mm f1.8 delivered. I tried it on my K-5 and noticed that the lens is struggling to autofocus and it keeps hunting. Tried in Auto, Av, P and Sv. The manual focus seems to be working.

I tried an 18-135mm WR lens to eliminate that it's not the camera body and I was able to take pictures without autofocus issues. So I am sure the camera body is working.

Any help would be much appreciated. I want to make sure it's faulty before returning.
Try it on the trepied, in good light and in LiveView; if it makes always the same, change it; good luck !
10-05-2017, 11:05 AM   #3
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 11,183
can you describe the issue a little more? Is the AF slow, or does it just never lock? Or does it lock focus, but the photo is misfocused?


QuoteOriginally posted by iamarunr Quote
Tried in Auto, Av, P and Sv. The manual focus seems to be working
This should not matter. Auto doesn't let you choose AF modes, but the others let you choose AF.S, AF.A or AF.C and AF point selection. Either way, this should not be a big effect on locking focus, only on where the camera looks for focus and whether it looks for focus once, or continuously.

The DA 50mm f1.8 is a really fast aperture lens, so it should be able to lock focus even in lower light conditions than the DA 18-135mm. But at wide apertures (low f-number), the Depth of focus will be very shallow, so the tolerance of "correct" focus is much higher. If you misfocus only a little at f1.8, it will be quickly visible.

General recommendations I can give:
a) Update camera firmware to the latest version. This is a good idea any time you are using a newer lens, just in case that lens wasn't included in the firmware. Note this can change some of your settings back to defaults. And you need to use a formatted SD card
b) Do a test with tripod and 2 sec timer, Centre point AF.S in good daylight, pointed at an obvious, contrasty subject.
c) Make sure lens is clean and free of damage, grime. Check the back lens element and camera mount. Check the aperture lever works normally

These might not fix the issue directly, but hopefully they will lead to indicators as to what the problem is.
10-05-2017, 11:17 AM   #4
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 5,867
The 18-135 can focus slightly closer so maybe if you were right at 45cm (kind of 17 and three-quarters in ultraprecise American inches) from the subject to the focal plane, the DA 50 f1.8 would appear to struggle. The 18-135 can focus at 40cm, a couple of inches less. Or you can have trouble close to infinity if the 50mm lens is not quite able to reach infinity. (In that case the lens should be returned.) The only other reason I can think of a normal focusing difference between these two lenses is that the 18-135 is set much wider. If it's at 18mm, just the subject being much smaller could give the AF system enough to lock, while the 50mm doesn't get there. Otherwise, the 50mm is letting in at least three times as much light to the AF sensors, so it ought to work great.

10-05-2017, 06:01 PM   #5
KDD
Veteran Member




Join Date: Sep 2013
Photos: Gallery | Albums
Posts: 403
Try to RESET your camera body!!!!
10-05-2017, 10:38 PM   #6
Junior Member




Join Date: Apr 2011
Location: Nashville
Posts: 38
Original Poster
Thanks everyone for your suggestions. I really appreciate it. I tried all the mentioned troubleshooting steps but no joy. I really love the lens though. I tried taking some shots in manual and the pictures are stunningly gorgeous. Can't wait to get the replacement and see how it turns out. Thanks again team! Cheers!

---------- Post added 10-06-17 at 12:38 AM ----------

QuoteOriginally posted by KDD Quote
Try to RESET your camera body!!!!
Tried this step but no luck.

---------- Post added 10-06-17 at 12:39 AM ----------

QuoteOriginally posted by Na Horuk Quote
can you describe the issue a little more? Is the AF slow, or does it just never lock? Or does it lock focus, but the photo is misfocused?



This should not matter. Auto doesn't let you choose AF modes, but the others let you choose AF.S, AF.A or AF.C and AF point selection. Either way, this should not be a big effect on locking focus, only on where the camera looks for focus and whether it looks for focus once, or continuously.

The DA 50mm f1.8 is a really fast aperture lens, so it should be able to lock focus even in lower light conditions than the DA 18-135mm. But at wide apertures (low f-number), the Depth of focus will be very shallow, so the tolerance of "correct" focus is much higher. If you misfocus only a little at f1.8, it will be quickly visible.

General recommendations I can give:
a) Update camera firmware to the latest version. This is a good idea any time you are using a newer lens, just in case that lens wasn't included in the firmware. Note this can change some of your settings back to defaults. And you need to use a formatted SD card
b) Do a test with tripod and 2 sec timer, Centre point AF.S in good daylight, pointed at an obvious, contrasty subject.
c) Make sure lens is clean and free of damage, grime. Check the back lens element and camera mount. Check the aperture lever works normally

These might not fix the issue directly, but hopefully they will lead to indicators as to what the problem is.

Great suggestions. Thank you for taking the time to write to me but it didn't work and I am shipping it back. Thanks though.
10-06-2017, 03:57 AM   #7
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 11,183
Yeah, sometimes you just get a lens that is not working properly Hope you get a great copy to enjoy next!
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!
af, aperture, auto, auto focus, autofocus, body, camera, check, da 50mm lens hunt, f1.8, firmware, focus, lens, pentax, pentax help, photography, smc, smc pentax da50mm, thanks, time, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Broken aperture on DA50mm/f1.8 OkiDoki Repairs and Warranty Service 5 07-02-2017 10:29 PM
Pentax DA50mm + 52mm Teleconverter :? wbgenetic Pentax SLR Lens Discussion 6 05-03-2016 08:56 AM
90mm 2.8 D FA 645 Macro Focus Hunting Issue r2studios Pentax Medium Format 9 02-17-2016 08:19 PM
Hunting lens or hunting camera? JohntheThird Troubleshooting and Beginner Help 18 05-08-2015 04:41 AM
Pentax DA50mm 1.8 fevbusch Pentax DSLR Discussion 9 02-04-2015 04:55 AM



All times are GMT -7. The time now is 08:55 AM. | 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