Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-15-2012, 05:28 PM   #1
Veteran Member
GabrielFFontes's Avatar

Join Date: Jul 2011
Location: Rio de Janeiro, Brazil
Posts: 647
Sigma 70-200 2.8 APO EX super frontfocus :(

Hi guys!
I finally got my Sigma 70-200 2.8 APO EX (no hsm, no macro, no os) MK1 lens
I'm already suffering from a severe frontfocus problem, even in bright daylight!
If i zoom in to 200mm, the image will come out out of focus, but at 70mm its fine
What can i do?
AF Fine Adjustment doesn't solve this...if i dial in some correction (with the help of debug), 200mm 2.8 will become sharp, but 70mm will become out of focus...
Can you guys help me?
I'll be travelling next week! :/

07-15-2012, 06:12 PM   #2
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,828
Out of curiosity, what focus distance are you using to make your assessments of FF/BF?

There is also something about effective focal length varying by subject distance that I recall being discussed here by some users of telephoto zooms like the Pentax 60-250. Your issues may relate to that.
07-15-2012, 06:19 PM   #3
Veteran Member
GabrielFFontes's Avatar

Join Date: Jul 2011
Location: Rio de Janeiro, Brazil
Posts: 647
Original Poster
Rawr, any focus distance.
40 meters, 5 meters, infinity, etc etc
Check out some examples :


So unlucky i've been waiting for this lens for 3 months
07-15-2012, 06:37 PM   #4
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,828
What AF mode were you using? Centre-spot? Then focus/recompose?

Remember too that the AF doesn't mean the little dots in the viewfinder are exactly where the focal point is. The AF works on horizontal or vertical regions of contrast, not little laser dots.

Also it doesn't look like you were shooting perpendicular to your target, but at an angle. Hence the focal plane was at an angle.

07-15-2012, 06:39 PM   #5
Veteran Member
vievetrick's Avatar

Join Date: Sep 2006
Location: Easthampton - Massachusetts - USA
Photos: Gallery
Posts: 5,175
Can I ask a way stupid question and please don't shoot me - what setting do you have the focus point at? Center/auto/select?
07-15-2012, 06:44 PM   #6
Veteran Member
Sol Invictus's Avatar

Join Date: Aug 2011
Location: Calgary, Alberta
Photos: Gallery
Posts: 392
Not really helpful but just wanted to quickly comment. When people ask for sample pictures to diagnose a problem, this is what they mean. Bravo!
07-15-2012, 06:47 PM   #7
Veteran Member
GabrielFFontes's Avatar

Join Date: Jul 2011
Location: Rio de Janeiro, Brazil
Posts: 647
Original Poster
Hi guys! I was using Center-spot autofocus and AF.S
I know that focus points are not exactly on the center, put they're not on the corner of the image either. :/
It's funny...
here is an example when the camera focused where i wanted
(although i think i had activated AF micro adjust on this one, not sure)

I'll test more tomorrow...
07-15-2012, 07:00 PM   #8
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,828
Shoot something square on (perpendicular) with some items before and in front of your focus target so that you can at least eliminate the fact that you are shooting at an angle from the equation... The classic row of AA batteries (or beer cans - whatever may be more practical for telephoto) springs to mind.

07-15-2012, 07:58 PM   #9
Veteran Member
GabrielFFontes's Avatar

Join Date: Jul 2011
Location: Rio de Janeiro, Brazil
Posts: 647
Original Poster
Hi guys!
I did a quick test using AA batteries as object, and it would still frontfocus
The funny thing is that it wouldn't take a sharp picture even when using live view (?)
And it can't be optical problem, since i took a couple of sharp pictures, right?
I'll test it in daylight again tomorrow
07-16-2012, 01:42 AM   #10
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,193
In the first shot it looks like the camera focused on the lines that cross in front of the white object.

Note that the AF areas are areas, not points. The test targets you chose are unsuitable to check for FF/BF.

The fact that even CDAF (LiveView) did not succeed, suggests that there may not be a lens FF/BF issue.

While of course it is possible that the lens has a FF/BF issue, you need to make a better of ensuring that the camera is presented with an unambiguous focus target.

You may want to consider my AF adjustment hints.
07-16-2012, 05:04 PM   #11
Pentaxian
Edgar_in_Indy's Avatar

Join Date: May 2010
Location: Indiana, USA
Photos: Gallery
Posts: 2,636
I don't think there's anything necessarily wrong with your lens. It sounds like the lens simply needs calibrated to your camera. If you were in the United States, I would just recommend that you send the camera and lens to Sigma to have the lens perfectly calibrated to the body. I did this with my Sigma 30mm 1.4, and they calibrated it and sent it back the same day they received it, and it came back focusing perfectly.

I sent it to Sigma in New York, and they performed the calibration for free, but I don't know what your options are in Brazil. But if I remember right, you practically stole the lens with the price you paid, so even if you have to pay to have it calibrated you're still getting a great deal.
07-16-2012, 09:32 PM   #12
Pentaxian
Edgar_in_Indy's Avatar

Join Date: May 2010
Location: Indiana, USA
Photos: Gallery
Posts: 2,636
According to the following page, Sigma's service center in Brazil is a place called "Digital Center" in Foz do Iguaçu in Paraná. Their telephone number is (45)3025-7740, and here is a link to their website:

:. Digital Center .:
07-17-2012, 11:42 AM   #13
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
I can;'t help but notice that you had previously posted about getting a lens like this and were having discussions with the seller about internal dust, and the lens would be cleaned before you got it.

I think this falls into the implied warranty that the lens was in good working condition.
07-17-2012, 12:47 PM   #14
Pentaxian
Edgar_in_Indy's Avatar

Join Date: May 2010
Location: Indiana, USA
Photos: Gallery
Posts: 2,636
QuoteOriginally posted by Lowell Goudge Quote
I think this falls into the implied warranty that the lens was in good working condition.
If it is just a matter of the lens and body not being in proper calibration to each other, then I don't think that necessarily means that the lens is not in working order. It happens all the time. That's why they put AF adjustment in so many camera bodies these days.

Also, I believe that the buyer got the lens at a very good price. And that's in Brazil, a country where electronics (including photography equipment) are very expensive, often double the price or more of the same items in the United States. So if I were him, I would sooner spend a little money to have the lens calibrated, rather than get in a dispute with the seller and/or return the lens.
07-17-2012, 02:10 PM   #15
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
QuoteOriginally posted by Edgar_in_Indy Quote
If it is just a matter of the lens and body not being in proper calibration to each other, then I don't think that necessarily means that the lens is not in working order. It happens all the time. That's why they put AF adjustment in so many camera bodies these days.

Also, I believe that the buyer got the lens at a very good price. And that's in Brazil, a country where electronics (including photography equipment) are very expensive, often double the price or more of the same items in the United States. So if I were him, I would sooner spend a little money to have the lens calibrated, rather than get in a dispute with the seller and/or return the lens.
Perhaps, but I have the same lens and I do not have issues with variable focus as a function of focus distance
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!
200mm, apo, frontfocus, guys, help, k-mount, pentax lens, sigma, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sigma 70-200/2.8 APO EX user impressions photogerald Pentax SLR Lens Discussion 32 08-12-2016 10:52 PM
Buying a Sigma 70-200 2.8 APO EX GabrielFFontes Pentax SLR Lens Discussion 24 07-14-2012 06:29 AM
For Sale - Sold: Sigma EX APO 70-200/2.8 Macroguy Sold Items 4 05-23-2012 01:25 PM
Difference between sigma 70-200 ex apo and apo ex dg mpg Pentax SLR Lens Discussion 3 06-28-2009 07:28 AM
For Sale - Sold: FS. Sigma 70-200 EX DG APO Duplo Sold Items 8 03-08-2007 06:35 PM



All times are GMT -7. The time now is 09:35 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