Forgot Password
Pentax Camera Forums Home
 

Closed Thread
Show Printable Version Search this Thread
11-13-2012, 09:17 AM   #1
New Member




Join Date: Nov 2012
Posts: 16
the damndest thing at 5.6

Last week i bought a Tamron 17-50 for my new k30.

Did some test shots at 17,24,35 and 50mm. Aperture 4.0 was what you would expect from this lens. 5.6 was blurry. (i know this lens quite well from my canon years)

I thought maybe the lens was bugged. Got me another one.
Same thing. 5,6 looked like out of focus.

Then I a third TAMRON. Again 5.6 really blurry.

Must be the camera right?


Last edited by mckracken; 11-16-2012 at 11:14 AM.
11-13-2012, 09:19 AM   #2
Inactive Account




Join Date: Dec 2008
Location: North Carolina
Photos: Albums
Posts: 1,720
Post some examples, it is impossible to tell without seeing it.
11-13-2012, 09:34 AM   #3
Senior Moderator
Loyal Site Supporter
Parallax's Avatar

Join Date: Apr 2008
Location: South Dakota
Photos: Gallery
Posts: 15,103
QuoteOriginally posted by mckracken Quote
Must be the camera right?
Not necessarily. The Tamron 24-75 that I had would focus or not depending on, well, I never did figure out what variables affected it; zoom position, aperture, Moon in the seventh house, Jupiter aligned with mars, whatever. It was a known phenomenon with the 24-75 and I have come across a few references of similar issues with the 17-50 Tamron, so it may not be an issue with the camera.
11-13-2012, 09:52 AM   #4
New Member




Join Date: Nov 2012
Posts: 16
Original Poster
Huh? But i bought a lens that says Tamron 17-50mm for Pentax?
Am i missing something? I tested 3 lenses. This is unbelievable.

Well, tomorrow im installing firmware 1.01. Wish me luck. (samples tomorrow)

11-13-2012, 10:07 AM   #5
Senior Moderator
Loyal Site Supporter
Parallax's Avatar

Join Date: Apr 2008
Location: South Dakota
Photos: Gallery
Posts: 15,103
I think it's unlikely that it's the camera. The camera isn't doing anything differently at f4.0 than at f:5.6. By f8.0 depth of field is sufficient to compensate for any focus shift characteristics of the lens.

diglloyd - Focus - Focus Shift and Spherical Aberration
11-13-2012, 10:08 AM   #6
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,318
Did you try focusing regularly, with PD AF, and also with live view (CD AF)? Using a tripod, defocusing manually between tests on a fixed subject. I doubt its a focusing problem, because the camera always uses AF with the lens wide open and then only stops down when taking the shot. So the problem might just be with the lens itself, but this is a popular lens so maybe someone who uses it a lot can chime in.
11-13-2012, 10:11 AM   #7
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 4,989
So if you focus, then turn off AF so you don't refocus between shots and take the exact same shot with f4 and f5.6, then f5.6 is blurrier? If you set it on manual focus and 5.6, if you hold down the optical preview and focus (so that you are focusing with the lens stopped down to 5.6), can you get a sharp shot then? (i.e. is a focus shift occuring?)
11-13-2012, 11:08 AM   #8
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,576
I have a Tamron 17-50, and it works fine on my K200D, K-x and K-5. I doubt it would suddenly work erratically on the K-30.

There are duds lenses out there, of course, but the issue you are describing is not one I've heard of with the Tamron. f5.6 is normally good at all focal lengths.

You probably need to revisit your testing technique to make sure you are doing everything precisely, and aren't seeing for example ordinary motion blur. You also need to say whether you were using AF or manually focussing. If you are just testing the lens optics, you don't need to use AF.

11-13-2012, 01:54 PM   #9
New Member




Join Date: Nov 2012
Posts: 16
Original Poster
been messing around real quick with liveview focus and viewfinder focus.

seems that the liveview AF works fine. (manual too)
the regular AF is a lot worse and almost unuseable.
11-13-2012, 02:00 PM   #10
Pentaxian
JinDesu's Avatar

Join Date: Jun 2011
Location: New York City
Photos: Gallery
Posts: 5,624
Well that's just.. weird. If it focuses at F2.8, it should focus at any aperture. Your camera checks focus at the widest aperture, and stops down after. So if there is nothing inherently wrong with the lens at F5.6 (from CDAF and manual focusing), then I don't know what to say..
11-13-2012, 02:52 PM   #11
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,576
QuoteOriginally posted by mckracken Quote
been messing around real quick with liveview focus and viewfinder focus. seems that the liveview AF works fine. (manual too)
the regular AF is a lot worse and almost unuseable.
Please describe the issue or problem more clearly.

You seem to be saying at f5.6, at all focal lengths, you get blurry images, but only with regular AF. However, when manually focussing, and when using liveview focus, your images are not blurry at f5.6.

This seemingly rules out any optical problems with the lens, or any problems with the AF mechanism in the lens too.

So the remaining things to look into are (a) the regular phase-detection 'viewfinder' AF and/or (b) your testing technique.

What settings have you been using for your viewfinder AF? And are you using anything like a UV filter on the lens?
11-13-2012, 03:08 PM   #12
New Member




Join Date: Nov 2012
Posts: 16
Original Poster
I will post back tomorrow, the hour is getting late.
thank you all so far for your interest in my problem.
11-14-2012, 06:20 AM   #13
New Member




Join Date: Nov 2012
Posts: 16
Original Poster
Expanded area af: off and on
Af active area selectable, center selected
af assist light on.
Shake RD on and off

I tried a lot of variations but the problem persists:
at 5.0 sharp, 5,6 blurry, 6.3 sharp again.
11-14-2012, 06:52 AM   #14
Site Supporter
altopiet's Avatar

Join Date: Sep 2010
Location: The Great Karoo, South Africa
Photos: Gallery | Albums
Posts: 1,915
Have you tested with any other lenses?
11-14-2012, 06:53 AM   #15
New Member




Join Date: Nov 2012
Posts: 16
Original Poster
(sorry cant edit my posts yet)

after another batch of tests, i did not get a sharp pic at 5.6 and above....
Closed Thread

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!
blurry, k-30, k-50, lens, pentax k30, pentax k50, tamron
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Tokina AT-X 80-400mm f/4.5-5.6 hiep2503 Sold Items 5 03-24-2012 08:54 PM
For Sale - Sold: Tokina AF 24-200mm f3.5-5.6 SD AT-X 242AF *LN* cheekygeek Sold Items 3 12-10-2011 01:38 PM
For Sale - Sold: Tokina AT-X II AF 80-400mm f/4.5-5.6 zoom for PENTAX mmzymxf Sold Items 3 08-01-2011 08:19 PM
For Sale - Sold: Tokina AT-X AF 80-400mm f/4.5-5.6 (near mint) (Worldwide) JP_Seattle Sold Items 4 01-09-2011 02:06 PM



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