Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-22-2009, 10:55 AM   #1
Senior Member




Join Date: Apr 2008
Location: Barcelona, Spain
Posts: 264
My DA* 50-135 and BF?

Hello.

I have been noticing on my lens some back focus issue. When shooting around f6.7 or f8 it seems quite normal, I have many portraits taken with this lens without advising the problem but when using the lens wide open the problem seems quite obvious, even landscapes photos seem a bit unsharp.

I did some tests on f2.8 and had to make 4 shots to have a sharp one, all the rest presented BF problem (I was shooting at about 2 meters of the object, f2.8, 1/250, ISO 200 and hand-held). In fact, it seems the lens get out-of-focus pictures randomly, no matter distance and F (I always shoot using AF).

I sent the pictures to the spanish Pentax Service and they told me that sometimes the problem is not on the lens itself but on the body, since it is the one who choose the focus point, or maybe it is a combination of my lens with my body (K10D).

They told me to send both lens and body for testing and maybe they only have to adjust the system without having to repair anything.

Did anybody had a similar problem? Will they make use of the in-camera hidden calibration menu to solve my problem?

Any similar experiences? I am afraid my problem wont get solved just cleaning the contacts... :-(

Thanks.

01-22-2009, 12:27 PM   #2
Senior Member
azcavalier's Avatar

Join Date: Oct 2007
Location: Blacksburg, VA
Photos: Gallery
Posts: 135
I had the same problem, with the same lens, and since i'm assuming you're talking about a K10D, the same camera. They said that they would adjust it for free (since the lens was less than a year old). But then I tried using the debug mode, and it now works great. Sharp as a tack.
01-22-2009, 12:32 PM   #3
Senior Member




Join Date: Apr 2008
Location: Barcelona, Spain
Posts: 264
Original Poster
Thanks for your answer... helps a lot to know more people having the same problem.

Yep, a K10D also... and after doing the debug mode adjust, did you have any issue with any other lens from your collection?

Thanks.
01-22-2009, 12:40 PM   #4
Senior Member
azcavalier's Avatar

Join Date: Oct 2007
Location: Blacksburg, VA
Photos: Gallery
Posts: 135
QuoteOriginally posted by cooldude14es Quote
Thanks for your answer... helps a lot to know more people having the same problem.

Yep, a K10D also... and after doing the debug mode adjust, did you have any issue with any other lens from your collection?

Thanks.
Nope. I'd post some here, but i'm not at my desk where I they're saved. I'll put them up in a few hours so you can see. But I should point out that I had noticed it with other lenses before as well. But the 50-135 is my main lens, and so that's the one I adjusted with. It's also my highest quality lens.

01-22-2009, 04:33 PM   #5
Veteran Member
Hannican's Avatar

Join Date: Oct 2007
Location: Irvine, CA
Photos: Gallery
Posts: 480
What is debug mode? And how does it work?
01-22-2009, 05:42 PM   #6
Senior Member
azcavalier's Avatar

Join Date: Oct 2007
Location: Blacksburg, VA
Photos: Gallery
Posts: 135
OK, here's the pictures to show you. Some of these were taken with my DA* 50-135, and some of them were taken with my Sigma 10-20 ultrawide. The first two are before I used debug mode, the rest are after.
Attached Images
         
01-22-2009, 06:23 PM   #7
Senior Member
azcavalier's Avatar

Join Date: Oct 2007
Location: Blacksburg, VA
Photos: Gallery
Posts: 135
QuoteOriginally posted by Hannican Quote
What is debug mode? And how does it work?
Debug mode can only be activated if you haven't upgraded your K10D to the latest firmware. If you have, you have to download an application and have it hooked up to your PC.

When it's activated, there is an extra menu option which allows you to tweak some settings. Most of them don't make much sense just by looking at them, but one of them is the focusing adjustment. So you can tweak back focus or front focus problems. The worry is that it only really works with the lens that you have on the camera as you mess with it. I found that it solved the problem for all my lenses.

Here's the link to the thread about it, which also has a link to the website where you can get the app. Also, if you just Google "K10D debug mode" you'll find lots of help and directions.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/27040-k10d-firmwar...unleashed.html

Also, I should add that one of the nice things about the K20D is that the ability to tweak the focus is included in the setup menu...without having to enter debug mode.
01-22-2009, 06:53 PM   #8
Veteran Member
Hannican's Avatar

Join Date: Oct 2007
Location: Irvine, CA
Photos: Gallery
Posts: 480
Thank You!

I believe my K10D experiences a little bit of a back focusing issue, which I've only noticed during "Focus Tests", so it's probably nothing I should mess with, but I will take a look at that link just in case it can help me make things better!

01-22-2009, 06:54 PM   #9
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by cooldude14es Quote
In fact, it seems the lens get out-of-focus pictures randomly, no matter distance and F (I always shoot using AF).
If its random, it isn't backfocus - it's simply a matter of the camera choosing a different subject to focus on than the one you intended. If there is a backfocus problem, it will be present on shot beyond a certain aperture, and in the same amount for a given focus distance. Posting some pictures would help, but you should also perofmr a focus test using a good test chart like the one at Home
01-23-2009, 12:44 AM   #10
Senior Member




Join Date: Apr 2008
Location: Barcelona, Spain
Posts: 264
Original Poster
Thank you all for your answer. Azcavalier, I think my BF is not so 'heavy' as yours was. In fact I did some portraits and it seemed ok, even landscapes seem ok...

I am posting some photos I took for checking the issue. I think I will also check with the focus chart later.

So, first one is the complete picture, no cropping. The focus point was on the white book (Vicente Segrelles). f2.8, 1/250, ISO 200, hand-held. The book on the right was about 6 inches behind.




And here it is a 100% crop of the focus point:




As you can see, it is out of focus. Next one is a 100% crop of the book on the right, which was a few inches behind:



This one is quite on focus.


I had to repeat the test 4 times to get a good one (focus on Vicente Segrelles), or at least a not so out-of-focus pictures on the white book.


Maybe the problem is based on what Marc says ('the camera choosing a different subject to focus on than the one you intended').

I have some walking around pictures with a similar problem, in fact it is more obvious when shooting close distances and wide open.

Ok, thanks for your comments.
01-23-2009, 05:37 AM   #11
Senior Member
azcavalier's Avatar

Join Date: Oct 2007
Location: Blacksburg, VA
Photos: Gallery
Posts: 135
Yeah, mine was really very obvious, and definitely not user error. Not that i'm not able to make mistakes... But look at those first two pictures! I had a lot of photos turn out like that with multiple lenses, and it was very consistent.
01-23-2009, 02:03 PM   #12
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by cooldude14es Quote
So, first one is the complete picture, no cropping. The focus point was on the white book (Vicente Segrelles).
...
Maybe the problem is based on what Marc says ('the camera choosing a different subject to focus on than the one you intended').
Were you using center-point mode or user-select mode with the center selected, or were you allowing the camera to choose the focus point? If you're sure the center focus point was being used, then this test looks like pretty good evidence, but I'd still use a chart. Real world tests leave too much room for error.
01-23-2009, 02:48 PM   #13
Senior Member




Join Date: Apr 2008
Location: Barcelona, Spain
Posts: 264
Original Poster
QuoteOriginally posted by Marc Sabatella Quote
Were you using center-point mode or user-select mode with the center selected, or were you allowing the camera to choose the focus point? If you're sure the center focus point was being used, then this test looks like pretty good evidence, but I'd still use a chart. Real world tests leave too much room for error.
I was using center-point mode. Yes, I think I will try using the chart.

In case a focusing problem exists, do you recommend using debug mode or sending the system to Pentax Service? Azcavalier case was obvious but mine is weird because I can not find a pattern, i mean, a BF problem should be always present but, as I told you, on my forth test the camera focused quite ok... so I dont think that playing on debug mode would help a lot.. Since I discovered the way to enter on debug mode using an exe file from the computer via USB I am really tempted..
01-23-2009, 04:17 PM   #14
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by cooldude14es Quote
In case a focusing problem exists, do you recommend using debug mode or sending the system to Pentax Service?
If it's inconsistent, that demonstrates the problem is *not* the straightforward one the debug mode adjustment is designed to workaround. So you'd probably find the results equally inconsistent after adjustment. I'd test like crazy to see if I could figure out where the problem *really* was, and not take any actual action until then. But assuming it does indeed turn out to be a real problem with the equipment that the debug mode adjustment can't fix, sending it in for service seems the only choice. I just wouldn't go there until I was sure where the problem was and how to reproduce it reliably and could explain it adequately. You'd hate to send the camera off, be without it several weeks, and then have it come back with a note saying "we couldn't find a problem".
01-24-2009, 09:40 AM   #15
Senior Member




Join Date: Apr 2008
Location: Barcelona, Spain
Posts: 264
Original Poster
Thanks for your help.. I will try to check both camera and lens deeply, and I will try to find somebody else owning a K10D to check lens with a different body, that would also help a lot.
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!
body, f2.8, focus, k-mount, lens, pentax lens, pictures, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Chinon 135 & Chinar 135 , Good Bad or Ugly seacapt Pentax SLR Lens Discussion 1 02-26-2010 09:03 PM
shoot out DA*50-135 v.s. A50 A*85 A100 A*135 Douglas_of_Sweden Pentax SLR Lens Discussion 42 12-11-2008 10:44 AM



All times are GMT -7. The time now is 10:55 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