Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-06-2010, 04:19 AM   #1
Senior Member




Join Date: Jul 2009
Location: Perth, Australia
Posts: 180
K-7 I think something is wrong :(

Hi Everyone

Hoping someone can help me out here. I'm not sure if this is a camera AF issue or lens issue.

I notice that my pictures are horribly out of focus (front focus) with my Sigma 100-300mm but I'm not sure what the cause is. Is it the lens or the AF?

Here are some test shots. Note that I don't recall having these issues on my Pentax K10D before I sold it and in camera focus adjustment doesn't improve the image.

This is AF focused at the "Focus Here' Text



This is AF focused just outside the square box



This is focused manually.



Unfortunately most of my lenses are MF and this is the only AF lens I've got. The only reason I just noticed it is because this is the first time I've used this lens on my K-7 since purchasing it in January.

Like I said, I haven't noticed this issue with my 100-300mm and the K10D before selling it.

Anyone able to shed some light onto the problem? I hope it's a camera issue and not lens as it's easier to replace the body then a lens, although both are still under warranty.

07-06-2010, 04:30 AM   #2
Veteran Member
Zebooka's Avatar

Join Date: May 2008
Location: Russia, Siberia, Novosibirsk
Posts: 323
1) Read camera's manual. K-7 has custom function for adjusting autofocus.
2) If correction range is not enough (using this custom function) - you can use debug mode and adjust AF there too.
07-06-2010, 04:40 AM   #3
Veteran Member




Join Date: Jul 2008
Location: Var, South of France
Photos: Albums
Posts: 1,071
And, I'd try with another AF lens (do you know someone around shooting Pentax?).
07-06-2010, 04:44 AM   #4
Senior Member




Join Date: Jul 2009
Location: Perth, Australia
Posts: 180
Original Poster
QuoteOriginally posted by Zebooka Quote
1) Read camera's manual. K-7 has custom function for adjusting autofocus.
2) If correction range is not enough (using this custom function) - you can use debug mode and adjust AF there too.
Already tired the in camera autofocus adjustment.

How do I get into the debug mode on the K-7 without affecting the warranty?

QuoteOriginally posted by dlacouture Quote
And, I'd try with another AF lens (do you know someone around shooting Pentax?).
No I don't have another AF lens but know someone who does although it's only a kit lens and not sure the IQ will be there to make a conclusive test.

07-06-2010, 07:24 AM   #5
Inactive Account




Join Date: Aug 2008
Location: Michigan, USA
Photos: Gallery | Albums
Posts: 7,484
Is it safe to assume you've tried the lens with a Real subject (not a paper chart)?

If you want to play with it, and haven't updated to the latest firmware,

Welcome to Pentax Hack

I mention the firmware because this is FW dependent and they don't have support for the latest. I could not get into the debug menu using these methods on mine. Keep in mind that the AF adjustment you make in the debug mode, will affect ALL lenses.

07-06-2010, 08:21 AM   #6
Pentaxian
aleonx3's Avatar

Join Date: Jul 2007
Location: Brampton, Ontario
Photos: Gallery | Albums
Posts: 3,888
Like JeffJS said, do you have the latest firmware update on it?

If it is a Pentax lens, you can send both to Pentax repair center to correct any focus errors (beyond the on camera adjustment limit I guess). Unfortunately, they will not be able to provide any support for third party lenses. That is one small thing (perhaps inconvenience) about getting non-Pentax lenses.
07-06-2010, 01:56 PM   #7
hcc
Pentaxian
hcc's Avatar

Join Date: Nov 2009
Location: Brisbane, Australia
Photos: Gallery | Albums
Posts: 3,531
To follow up the post of aleonx3, did you buy new both the Pentax K-7 body and Sigma lens ?

In the affirmative, both Pentax and Sigma are distributed in Australia by CR Kennedy, and you should contact them straight away as part of the warranty.

More, you may contact directly CR Kennedy about the Pentax debug functions. CRK is approachable as several AUS Pentaxians know and they may be able to assist you.
07-06-2010, 02:03 PM   #8
Veteran Member




Join Date: Jul 2009
Posts: 1,296
For those chart tests to be accurate, you need the paper lined up properly and the camera on the right angle too

07-06-2010, 05:26 PM   #9
Pentaxian
aleonx3's Avatar

Join Date: Jul 2007
Location: Brampton, Ontario
Photos: Gallery | Albums
Posts: 3,888
I would have preferred testing focus accuracy (or for lack of accuracy) using AA batteries lined up one another and take test shots aiming at the middle one. Of course Aperture has to be reasonably wide open.
07-06-2010, 05:30 PM   #10
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Testing using batteries is nowhere near as precise as using a well-designed test chart, but either way, you do have to set the test up correctly.
07-06-2010, 05:37 PM   #11
Pentaxian
aleonx3's Avatar

Join Date: Jul 2007
Location: Brampton, Ontario
Photos: Gallery | Albums
Posts: 3,888
QuoteOriginally posted by Marc Sabatella Quote
Testing using batteries is nowhere near as precise as using a well-designed test chart, but either way, you do have to set the test up correctly.
Marc, I agree. I was thinking of "lack of" accuracy by wide margin can sometimes be easily tested using that method.
07-06-2010, 08:35 PM   #12
Senior Member




Join Date: Jul 2009
Location: Perth, Australia
Posts: 180
Original Poster
Thanks for the replies everyone.

Yes, the test was conducted at the right angle (45 deg).

I had the zoom set to 300mm and f4, hence why it's slighly scewed to one side. That in reality shouldn't affect focus to that degree anyway.

No matter what f stop I used, all my images were out of focus. Focus issues were most visible from 200mm onwards hence why I used the 300mm setting.

I will be contacting CR Kennedy here in Perth and talking to them directly about warranty. I will have to test with another Pentax AF lens first to make sure it's not my K-7 that's faulty.

EDIT: Yes I have the latest firmware on my K-7.

Last edited by CrazyNuts; 07-06-2010 at 08:42 PM.
07-06-2010, 09:09 PM   #13
Pentaxian
jeffshaddix's Avatar

Join Date: Jun 2010
Location: Albuquerque, NM
Posts: 1,371
It could very well be the lens. While I love Sigma's IQ, they have a really bad habit of screwing up with front/back focusing. If you find out it's the lens and not the camera (which I doubt), Sigma will be happy to calibrate it for you.
07-06-2010, 09:16 PM   #14
Inactive Account




Join Date: Aug 2008
Location: Michigan, USA
Photos: Gallery | Albums
Posts: 7,484
QuoteOriginally posted by CrazyNuts Quote
Thanks for the replies everyone.

Yes, the test was conducted at the right angle (45 deg).

I had the zoom set to 300mm and f4, hence why it's slighly scewed to one side. That in reality shouldn't affect focus to that degree anyway.

No matter what f stop I used, all my images were out of focus. Focus issues were most visible from 200mm onwards hence why I used the 300mm setting.

I will be contacting CR Kennedy here in Perth and talking to them directly about warranty. I will have to test with another Pentax AF lens first to make sure it's not my K-7 that's faulty.

EDIT: Yes I have the latest firmware on my K-7.
A different lens will likely yield different results.

When I try to use that focus chart, I have a stand made that holds the chart at 45 degrees and keeps it completely flat. That way, I can just move closer or further away from the chart. As long as I've set the camera to the same height as the focus line, and leveled the camera (on a tripod), I don't have to worry about getting the angle of the camera correct. The chart holder does that for me.

Another thing to keep in mind, if it hasn't been mentioned, at maximum aperture, the DOF is rather thin on any lens. At 300mm it might help to pull back some (see above) if you are going to test at f4. The closer you get, the thinner the DOF (as you probably already know).

Lastly, Incandescent light is murder on those focus charts. It would benifit you to set up an outdoor rig in natural light. With indoor lighting (unless we are talking about studio lighting), a given lens can (and has been) dead on with the first shot, and 20mm front (or back) focused on the next. Same lens, No adjustments except to re-focus.

Lastly (really this time) I THINK that when you do a Zoom lens, you are supposed to do it mid zoom range (200mm on your Sigma).

Anyway, Good luck with it. Let us know how you make out.

07-07-2010, 02:20 AM   #15
Senior Member




Join Date: Jul 2009
Location: Perth, Australia
Posts: 180
Original Poster
QuoteOriginally posted by JeffJS Quote
A different lens will likely yield different results.

When I try to use that focus chart, I have a stand made that holds the chart at 45 degrees and keeps it completely flat. That way, I can just move closer or further away from the chart. As long as I've set the camera to the same height as the focus line, and leveled the camera (on a tripod), I don't have to worry about getting the angle of the camera correct. The chart holder does that for me.

Another thing to keep in mind, if it hasn't been mentioned, at maximum aperture, the DOF is rather thin on any lens. At 300mm it might help to pull back some (see above) if you are going to test at f4. The closer you get, the thinner the DOF (as you probably already know).

Lastly, Incandescent light is murder on those focus charts. It would benifit you to set up an outdoor rig in natural light. With indoor lighting (unless we are talking about studio lighting), a given lens can (and has been) dead on with the first shot, and 20mm front (or back) focused on the next. Same lens, No adjustments except to re-focus.

Lastly (really this time) I THINK that when you do a Zoom lens, you are supposed to do it mid zoom range (200mm on your Sigma).

Anyway, Good luck with it. Let us know how you make out.

I had my tripod set to 45 deg. I used a clinometer to confirm my angle; and I was about 2m away from the sheet of paper due to min focus distance requirements with this lens.

I tried all F stops and all yelded the same results. There was only a very marginal improvement at higher F stops.

The reason I chose 300mm is because that's when the problem was most prominent. You could see it at 200mm but 300mm really exacerbated the issue.

Yes, I also tried it in realy word situations and that's when I initially noticed the problem, hence my further testing.

Also my light source wasn't incandescent. It was a standard halogen globe.
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!
100-300mm, af, camera, dslr, focus, issue, k-7, k10d, lens, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
sometimes it is just wrong devisor Post Your Photos! 5 07-24-2009 12:19 PM
What am I doing wrong here ? holdgaj Troubleshooting and Beginner Help 9 04-30-2009 10:40 PM
what have I done wrong here? johngs Post Your Photos! 12 01-28-2009 01:58 AM
What's right and what's wrong? dws1117 Photo Critique 2 01-08-2008 09:13 PM
Help! What am I doing wrong? clarenceclose Pentax DSLR Discussion 21 04-08-2007 06:09 AM



All times are GMT -7. The time now is 11:11 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