Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-24-2016, 07:51 AM   #1
New Member




Join Date: Apr 2016
Posts: 5
Disappointing Continuous Autofocus AF-C with K-S2 and 18-135WR

New Pentax owner here (well, not so new, I have a Spotmatic II and some Super Takumars)! I just recently got a K-S2 and 18-135WR as a weather-sealed kit to complement my Micro Four Thirds kit. The weather resistance and fully articulated screen were the main advantages, but I was also hoping that it would improve on the Continuous Autofocus performance of my mirrorless camera.

I went out to test the AF-C with my dog at the park, and I was really disappointed with the hit-rate. Probably less than 10% of the shots had the focus nailed properly. Now granted, despite how mundane it is, I realize that having a dog running quickly and erratically towards the camera is probably one of the single most difficult conditions to test a camera's autofocus, but I found that often his tail or hindquarters will be in sharp focus rather than his face, so I know it's not insufficient shutter speed. It's like the camera locked focus on the right plane and then took the photo a split second afterwards rather than continuously adjusting it.



Mostly was shooting with these settings:

Tv @ 1/800s
AF-C
Continous High burst rate
Auto-5 or Spot AF point

I guarantee that my technique could be improved, and I know many people have been able to get good results with this AF system on the K5 II. I guess my main question is whether I simply have much too high an expectation about the continuous autofocus performance of any <$1000 camera, or if there are settings and techniques that I should be using instead to get better results?

Would AF-A be better than AF-C?
Would SEL-Expanded be better than Auto-5 or Spot AF point modes?
Can the AF motor in the 18-135 keep up properly with this kind of shooting?

I don't think the lens is backfocusing, since it seems to work fine and deliver sharp results in static conditions, but I am out of my element when it comes to AF micro-adjustment, having come from a background of manual focus film and then a variety of digital cameras without mirrors, so I might be missing something!

I do this kind of shooting rarely, so it's not a top priority and I am sure I will enjoy the camera plenty for its originally intended applications on camping trips, winter, and rainy days, but I just want to make sure I'm not missing anything totally obvious and getting an unfair impression of the camera.

Thanks in advance, any tips, tricks, and recommendations are greatly appreciated!

04-24-2016, 08:32 AM   #2
amp
Site Supporter




Join Date: Dec 2015
Posts: 163
I, like you, don't do much action shooting, but I will say that my results improved when I started using back button af. It seems that the camera does a better job of doing two things at the same time.
04-24-2016, 08:46 AM   #3
Loyal Site Supporter




Join Date: Jun 2014
Location: Los Angeles, CA (San Gabriel Valley region)
Photos: Albums
Posts: 205
Along with back button, I use center point focus. That way I can control what I am focusing on rather than let the camera decide.

It took some practice with center point only but I get a higher hit rate now.

Not sure if that was the 'right' way, but it works for me. Someday I'll learn to use the full array of focus points.
04-24-2016, 09:33 AM   #4
Forum Member
FozzFoster's Avatar

Join Date: Jan 2016
Location: Alberta
Posts: 62
In the Live View settings, you can find tracking-focus. It's not the best I've seen at tracking, but that may also help you photograph your pets(?)

04-24-2016, 12:28 PM   #5
Loyal Site Supporter
clackers's Avatar

Join Date: Jul 2013
Location: Melbourne
Photos: Albums
Posts: 9,017
I use screwdrive lenses for sport and action, Turbofrog. But if you want to keep using yours on this situation, switch to MF, zone focus and take a burst as your dog enters it.

As a film/SuperTak user I'm sure you know the drill.

04-24-2016, 12:59 PM   #6
Senior Member




Join Date: Jul 2015
Photos: Gallery
Posts: 104
1/800 seems overkill to freeze the motion of a dog jogging toward you. I would bring that down a bit so you can raise your aperture. I don't know what you shot at but it looks like the field of view is very small. With a moving subject and a small F stop I don't think you will get the results you are looking for without something like clackers mentioned (catch in focus)
04-24-2016, 02:08 PM   #7
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,128
I would recommend trying 11-point mode. Also, make sure that "focus priority" is selected in the custom function menu. Using the back button to focus is also a good recommendation, so I would experiment with that.

The 18-135mm obviously isn't the best choice for tracking because of the slower aperture, but it should still allow you to get sharp photos in a daytime scenario like this one. Give it another try and hopefully you'll get better results

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

04-24-2016, 02:35 PM   #8
Loyal Site Supporter




Join Date: Jun 2014
Location: Los Angeles, CA (San Gabriel Valley region)
Photos: Albums
Posts: 205
QuoteOriginally posted by Adam Quote
I would recommend trying 11-point mode. Also, make sure that "focus priority" is selected in the custom function menu. Using the back button to focus is also a good recommendation, so I would experiment with that.

The 18-135mm obviously isn't the best choice for tracking because of the slower aperture, but it should still allow you to get sharp photos in a daytime scenario like this one. Give it another try and hopefully you'll get better results
Does the 11-point AF system recognize eyes vs tail on deciding what to keep on focus?

04-24-2016, 03:10 PM   #9
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 43,128
QuoteOriginally posted by realitarian Quote
Does the 11-point AF system recognize eyes vs tail on deciding what to keep on focus?
I think that would be asking for a bit much But it should try to keep the closest point in focus.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

04-24-2016, 10:54 PM   #10
Senior Member




Join Date: Oct 2015
Posts: 216
QuoteOriginally posted by Turbofrog Quote
New Pentax owner here (well, not so new, I have a Spotmatic II and some Super Takumars)! I just recently got a K-S2 and 18-135WR as a weather-sealed kit to complement my Micro Four Thirds kit. The weather resistance and fully articulated screen were the main advantages, but I was also hoping that it would improve on the Continuous Autofocus performance of my mirrorless camera.

I went out to test the AF-C with my dog at the park, and I was really disappointed with the hit-rate. Probably less than 10% of the shots had the focus nailed properly. Now granted, despite how mundane it is, I realize that having a dog running quickly and erratically towards the camera is probably one of the single most difficult conditions to test a camera's autofocus, but I found that often his tail or hindquarters will be in sharp focus rather than his face, so I know it's not insufficient shutter speed. It's like the camera locked focus on the right plane and then took the photo a split second afterwards rather than continuously adjusting it.



Mostly was shooting with these settings:

Tv @ 1/800s
AF-C
Continous High burst rate
Auto-5 or Spot AF point

I guarantee that my technique could be improved, and I know many people have been able to get good results with this AF system on the K5 II. I guess my main question is whether I simply have much too high an expectation about the continuous autofocus performance of any <$1000 camera, or if there are settings and techniques that I should be using instead to get better results?

Would AF-A be better than AF-C?
Would SEL-Expanded be better than Auto-5 or Spot AF point modes?
Can the AF motor in the 18-135 keep up properly with this kind of shooting?

I don't think the lens is backfocusing, since it seems to work fine and deliver sharp results in static conditions, but I am out of my element when it comes to AF micro-adjustment, having come from a background of manual focus film and then a variety of digital cameras without mirrors, so I might be missing something!

I do this kind of shooting rarely, so it's not a top priority and I am sure I will enjoy the camera plenty for its originally intended applications on camping trips, winter, and rainy days, but I just want to make sure I'm not missing anything totally obvious and getting an unfair impression of the camera.

Thanks in advance, any tips, tricks, and recommendations are greatly appreciated!
were you using your camera in live view??

live view doesn't provide the fastest results in focusing (unless you have on sensor phase detection like canon). If you're using OVF & still getting bad results then I guess it could also be lens issue.

Also I've heard Pentax AF-C isn't that good like Nikon or even Canon, (may be now they have improved with K-3 & K-3 II but not sure about K-S2).
04-25-2016, 05:38 AM   #11
New Member




Join Date: Apr 2016
Posts: 5
Original Poster
Thanks for the useful suggestions, everyone!

I've been thinking about using back-button AF generally, this might be the incentive I need to give it a shot in earnest. It surprises me that BBAF would work better than simply keeping the shutter half-depressed in AF-C, but it's worth a shot.

Catch-in focus is another one I hadn't thought of that's definitely worth trying.

In most of those shots I was between f/5.6 and f/8, which really doesn't seem like too large an aperture for a situation like this at <135mm. 1/800s was what I switched to after some early shots (mostly at 1/400s) so as to completely rule out motion blur from my testing. After all, people use the 200mm/2.8 and 300mm/f4 wide open, which have much longer focal lengths and so much shallower depth of field.

I'll also try 11-point AF. My thinking was to limit it entirely to the smaller central area or to use the center point only and keep the center point entirely on my dog's head as I was following him so that the AF wouldn't get confused and focus somewhere else on his body. But maybe with the additional flexibility of 11-point the camera can make smarter decisions after all?

I was definitely using the OVF / PDAF for all the shots in the park, but afterwards I briefly tried the Live View / Contrast AF Tracking, but it's noticeably worse than my Panasonic which itself is not particularly good at continuous focusing since it uses contrast detect AF only.
04-25-2016, 06:18 AM   #12
Senior Member




Join Date: Oct 2015
Posts: 216
QuoteOriginally posted by Turbofrog Quote
Thanks for the useful suggestions, everyone!

I've been thinking about using back-button AF generally, this might be the incentive I need to give it a shot in earnest. It surprises me that BBAF would work better than simply keeping the shutter half-depressed in AF-C, but it's worth a shot.

Catch-in focus is another one I hadn't thought of that's definitely worth trying.

In most of those shots I was between f/5.6 and f/8, which really doesn't seem like too large an aperture for a situation like this at <135mm. 1/800s was what I switched to after some early shots (mostly at 1/400s) so as to completely rule out motion blur from my testing. After all, people use the 200mm/2.8 and 300mm/f4 wide open, which have much longer focal lengths and so much shallower depth of field.

I'll also try 11-point AF. My thinking was to limit it entirely to the smaller central area or to use the center point only and keep the center point entirely on my dog's head as I was following him so that the AF wouldn't get confused and focus somewhere else on his body. But maybe with the additional flexibility of 11-point the camera can make smarter decisions after all?

I was definitely using the OVF / PDAF for all the shots in the park, but afterwards I briefly tried the Live View / Contrast AF Tracking, but it's noticeably worse than my Panasonic which itself is not particularly good at continuous focusing since it uses contrast detect AF only.
do post your experience after you have shot using the improved settings. :-)

Hopefully the K-S2 will do better now

Last edited by anu l; 04-25-2016 at 06:52 AM.
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, af-c, af-c with k-s2, autofocus, autofocus af-c, camera, dog, focus, k-s1, k-s2, performance
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Pentax K-S2 with 18-135 WR Lens rrwilliams64 Sold Items 4 04-15-2016 09:38 AM
Continuous and Single Shot AF with the Back Button nanhi Pentax DSLR Discussion 4 01-27-2016 02:36 PM
K-S2 with 18-135 Lens photo dawn Pentax Price Watch 31 06-21-2015 03:20 PM
K-S2+18-135WR Kit Setter Dog Pentax DSLR Discussion 17 02-19-2015 05:50 PM



All times are GMT -7. The time now is 09:34 PM. | 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