Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-07-2012, 08:35 PM   #16
Senior Member




Join Date: Jul 2011
Location: Tokyo
Posts: 115
ok so can you guys explain a way to over come this problem does zooming in focusing and zooming out solves the problem

05-07-2012, 08:42 PM   #17
Pentaxian
twitch's Avatar

Join Date: Nov 2009
Posts: 4,571
QuoteOriginally posted by nirVaan Quote
ok so can you guys explain a way to over come this problem does zooming in focusing and zooming out solves the problem
Only if you have a parafocal lens like the DA*50-135
05-08-2012, 05:01 AM   #18
Senior Member




Join Date: Jul 2011
Location: Tokyo
Posts: 115
i dont know about the OP but this is my only zoom others are all prime and they focus really well.and btw how do you know if a zoom is a parafocal or not
05-09-2012, 02:25 AM   #19
Forum Member




Join Date: Dec 2010
Location: Silkeborg, Denmark
Posts: 82
Original Poster
Does anyone know if the AF areas are square or rectangular?

If they are rectangular in shape, I guess some precision could be gained from holding the camera vertically when shooting mountain bikers head on.
Or using the long AF points in the sides, those that are shown as a line, assuming of course that these AF points are rectangular.

05-09-2012, 03:11 AM   #20
Pentaxian
twitch's Avatar

Join Date: Nov 2009
Posts: 4,571
QuoteOriginally posted by mikknu Quote
Does anyone know if the AF areas are square or rectangular?

If they are rectangular in shape, I guess some precision could be gained from holding the camera vertically when shooting mountain bikers head on.
Or using the long AF points in the sides, those that are shown as a line, assuming of course that these AF points are rectangular.
Af points are cross type, as in they look like a plus sign --> +
05-09-2012, 07:28 AM   #21
Forum Member




Join Date: Dec 2010
Location: Silkeborg, Denmark
Posts: 82
Original Poster
QuoteOriginally posted by twitch Quote
Af points are cross type, as in they look like a plus sign --> +
Does that mean it will mainly focus along the cross lines, picking whatever fits AF criteria the most?
05-09-2012, 07:56 AM   #22
Pentaxian




Join Date: Feb 2010
Location: East Bay Area
Photos: Gallery
Posts: 775
Btw, were you pre-focusing on the incoming biker location and then took the shot when she came into the frame or were you trying to catch it on the fly? I did a few tests a couple days ago trying to catch the back of the bikers who rode past by me. By the time the camera can confirm focus and then I took the shot, the biker is already slightly blurred because they have moved from camera's focus point and I can see the ground slightly behind the biker (where the biker was when the camera confirmed focus) is totally in focus.
05-10-2012, 03:38 AM   #23
Forum Member




Join Date: Dec 2010
Location: Silkeborg, Denmark
Posts: 82
Original Poster
QuoteOriginally posted by ruggiex Quote
Btw, were you pre-focusing on the incoming biker location and then took the shot when she came into the frame or were you trying to catch it on the fly? I did a few tests a couple days ago trying to catch the back of the bikers who rode past by me. By the time the camera can confirm focus and then I took the shot, the biker is already slightly blurred because they have moved from camera's focus point and I can see the ground slightly behind the biker (where the biker was when the camera confirmed focus) is totally in focus.
I do tend to pre-focus, but the AF system will still start focusing on whatever has the most contrast or is the most lit. I was out yesterday and got around 96 usable pictures and about 78 where the focus had mainly fallen on some grass/moss in the background, a few had focus in the foreground, again grass in focus. It could almost seem like my K-5 have a fondness for bright green forest growth.

It can focus on the background even though the rider is entirely in focus and wearing bright colours, maybe grass reflect light better or something, but it is annoying me a fair bit now.

This picture is an example of focus landing on the hill behind the rider, though it is not as pronounced as some of the other pictures I took, can't show one of those because I haven't had the time to upload one yet:
All sizes | IMGP2531 | Flickr - Photo Sharing!

Same goes for this picture, different place, not sure if the reason is wrong focus, actual back focus, the lens focusing too slowly or the rider just being too fast:
IMGP2634 | Flickr - Photo Sharing!

05-10-2012, 07:10 AM   #24
Pentaxian




Join Date: Feb 2010
Location: East Bay Area
Photos: Gallery
Posts: 775
QuoteOriginally posted by mikknu Quote
I do tend to pre-focus, but the AF system will still start focusing on whatever has the most contrast or is the most lit. I was out yesterday and got around 96 usable pictures and about 78 where the focus had mainly fallen on some grass/moss in the background, a few had focus in the foreground, again grass in focus. It could almost seem like my K-5 have a fondness for bright green forest growth.

It can focus on the background even though the rider is entirely in focus and wearing bright colours, maybe grass reflect light better or something, but it is annoying me a fair bit now.
Have you tried your Sigma again (using same f stop) now you probably have better understanding of your camera's focus behavior and compare the results? Do you have the option of trying different copy of DA 50-135? If the results are so much better with either case, there might be something wrong with your copy of the 50-135. If the results are about the same, then it's something else.

I don't shoot action shots too often but I do notice that whenever I'm in a hurry the chance of getting wrong focus is way higher because the K-5 likes to pick focus point that's not really my intention. When I do have time to carefully pick my focus point, there are definitely times when I'd focus on something using only the center point and the focus is still a bit off. I'd move like 1mm to the side and it would pick the right focus on the second try. Like Marc said earlier, the camera's software algorithm will pick whatever is the "easiest" point for it to focus on, which may not be your intended point. In the case where I pre-focus for a shot, I also turn to MF after pre-focusing so that the camera doesn't try to out smart me when taking the actual shot.

Last edited by ruggiex; 05-10-2012 at 07:16 AM.
05-10-2012, 10:42 AM   #25
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by nirVaan Quote
ok so can you guys explain a way to over come this problem
Sure - don't rely on AF for subjects smaller than AF sensors. Meaning, either pick something large to focus on (eg, a person's torso rather than face), or switch to MF for that shot (one reason I pretty much won't consider an AF lens without quick shift).
05-10-2012, 01:56 PM   #26
Forum Member




Join Date: Dec 2010
Location: Silkeborg, Denmark
Posts: 82
Original Poster
QuoteOriginally posted by Marc Sabatella Quote
Sure - don't rely on AF for subjects smaller than AF sensors. Meaning, either pick something large to focus on (eg, a person's torso rather than face), or switch to MF for that shot (one reason I pretty much won't consider an AF lens without quick shift).
Taking into account that the DA*50-135 is apparently par-focal and a bit slow at focusing, same goes for the K-5, could it be possible to use that to my advantage by zooming in to focus with AF-C and then quickly zoom out and hit the shutter button in one swift go to capture the image?
I know it sounds unlikely, but I will try that on Sunday during the next race.
05-10-2012, 10:25 PM   #27
Forum Member




Join Date: Dec 2010
Location: Silkeborg, Denmark
Posts: 82
Original Poster
QuoteOriginally posted by ruggiex Quote
Have you tried your Sigma again (using same f stop) now you probably have better understanding of your camera's focus behavior and compare the results? Do you have the option of trying different copy of DA 50-135? If the results are so much better with either case, there might be something wrong with your copy of the 50-135. If the results are about the same, then it's something else.
I probably should try out the Sigma again in order to compare results. I decided to go with the DA* because I wanted less focal length, yet still have some zoom. Keeping in mind that the K-5 works better if zoomed in, standing at the same distances the Sigma could get better focus due to the fact that it is more zoomed in and the subject therefore is larger in the viewfinder. It's a theory anyway.

I did have 3 races in a row with the DA* where the majority of pictures were in focus as intended, more or less, which is why I think Marc made a good case towards the large sensor points being my actual problem.
05-14-2012, 03:36 AM   #28
Forum Member




Join Date: Dec 2010
Location: Silkeborg, Denmark
Posts: 82
Original Poster
Another day out

Yesterday I was out again, used mainly AF-S to set a focus point and then switched to MF on the DA*. It worked a charm but I can see on several images that the focus point is still behind what I focused on, as can be seen on the picture below, where I focused on the blue mat, yet the PoF is behind it.


I found out early, so I just worked around it, but had it been a more sporadic sport like soccer/football, I still have the feeling it wouldn't work well.
The few times I did try AF-C, it gave the same poor focus results, only nailing it on one image. I did however have sucess with panning shots using the catch-in-focus option + trailing curtain with flash on.
All in all a lot more manual work on my behalf but it worked out great

Still can't figure out if this is suppose to be normal behaviour or not.
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!
adjustment, af, da*, f/2.8, focus, issues, k-mount, lens, light, model, pentax lens, slr lens, window
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Focus problems with the DA 18-135? dshombert Pentax SLR Lens Discussion 4 02-16-2012 06:45 AM
DA* Focus Ring 50-135 Problem AMBIVALENCE Pentax SLR Lens Discussion 2 06-21-2011 09:25 PM
DA* 50-135 vs 60-250: focus breathing? Loren E Pentax SLR Lens Discussion 2 04-16-2011 08:33 PM
18-135 mm auto focus Jed Mooar Pentax SLR Lens Discussion 3 03-21-2011 06:48 PM
K10 Focus screen confusion Steve Beswick Pentax DSLR Discussion 5 05-18-2009 09:46 AM



All times are GMT -7. The time now is 12:20 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