Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-13-2009, 07:32 AM   #1
Pentaxian
seacapt's Avatar

Join Date: Nov 2008
Location: North Carolina , USA
Photos: Gallery
Posts: 2,252
I don't know jack about lenses

First I gotta say I LOVE my Pentax DSLRs and some of my Pentax lenses.
Secondly if you don't want to hear negative thoughts on Pentax Imaging Co. please stop reading now.
When I bought my wife her K20d I purchased a FA 28-105 /3.2 with it. She allways complained that the auto focus was bad and manual focus was hit or miss. I thought it was just her. I borrowed this lens recently to shoot a martial arts tournament (my son's first time competing at black belt level). To my surprise and dismay every shot (100 +) had the spectators in the background in perfect focus but the competitors either out or very soft. when I calmed down I did test shots on my K20 and my istDL the results were the same , bad back focus. I sent the lens to Pentax under warranty 3weeks ago and got it back yesterday.Pentax was kind enough to tell me that the lens was functioning perfectly and I quoate "Your digital cameras were designed to be used with digital lenses , please buy digital lenses or use a smaller f stop".
Sorry folks but this p-ssed me off! One of the reasons I bought into the Pentax line was their proud claim of abillity to use fine vintage glass. I have intentionally bought only full frame lenses because I have not given up film and have considered switching to Pentax for film cameras as well. The lenses listed in my signature are only a few from my collection that I really like and would endorse to others . I also own or have owned several other Pentax full frame AF lenses, not one ( F or FA ) have had any focusing problems. I guess I just don't know jack about photography cause Pentax told me so! Great customer service and educational too.
Sorry for venting but I wondered if anyone has had simillar experiences.
Anyone want to buy a like new "perfectly opperating" FA 28-105?

05-13-2009, 07:40 AM   #2
Site Supporter
Nowhere Matt's Avatar

Join Date: Nov 2007
Location: Nowhere Land
Photos: Gallery | Albums
Posts: 2,312
Maybe the lens saw someone in the crowd it thought it knew and was distracted. Is the lens single and was simply looking for interesting people to meet? Why don't you take the lens to a bar some night and just be "wingman" for the lens for a change.
05-13-2009, 08:00 AM   #3
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
Does "back focus" apply to the sort of distances one would expect between participants and spectators? Sounds more like it was just focusing on the spectators to begin with. What focus mode were you using? What AF point?

Jackass on the phone and possible camera/lens problems aside....it is still up to the photographer to make sure his subject is in focus before pressing the shutter.

Last edited by Mike Cash; 05-13-2009 at 09:08 AM.
05-13-2009, 08:32 AM   #4
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,231
All sarcasm aside, the most likely explanation is that the camera locked on the crowd rather than the intended subject. That is one of the main issues I have with AF. You are never really sure what the camera is focusing on. You might want to try locking the AF point at the center spot.

Steve

05-13-2009, 08:35 AM   #5
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,763
QuoteOriginally posted by stevebrot Quote
All sarcasm aside, the most likely explanation is that the camera locked on the crowd rather than the intended subject. That is one of the main issues I have with AF. You are never really sure what the camera is focusing on. You might want to try locking the AF point at the center spot.

Steve
One of my pet peeves as well. Good suggestion.
05-13-2009, 08:38 AM   #6
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
For the record, I wasn't being sarcastic anywhere in my post. My initial question was a serious one. I practically never use AF lenses so this whole front/back focus thing is Greek to me. But since it doesn't seem likely they designed a focus adjustment range of several meters into the K20D I had to surmise that the proplem was lack of attention to what the camera was focusing on and failure to adjust settings accordingly.
05-13-2009, 09:06 AM   #7
Pentaxian
seacapt's Avatar

Join Date: Nov 2008
Location: North Carolina , USA
Photos: Gallery
Posts: 2,252
Original Poster
QuoteOriginally posted by stevebrot Quote
You might want to try locking the AF point at the center spot.
was shooting in AV with center spot focus. lens was stopped down as much as possibleunder conditions , don't remember #'s. Also did static tests on tripod later.

QuoteOriginally posted by Mike Cash Quote

Jackass on the phone .
They put it in writing! Also sent me a copy of page 106 from the k20D manual "AF Adjustment.
05-13-2009, 09:21 AM   #8
Pentaxian
seacapt's Avatar

Join Date: Nov 2008
Location: North Carolina , USA
Photos: Gallery
Posts: 2,252
Original Poster
QuoteOriginally posted by Mike Cash Quote
Does "back focus" apply to the sort of distances one would expect between participants and spectators? Sounds more like it was just focusing on the spectators to begin with. .
Most regional tournements are held in highschool gyms which are divided into 8-10 small rings. Spectators may be as close as 6Ft. from contestants and judges even closer. My point is that everything 12 in. or so beyond the subect was in focus.
Static test distances varied depending on f stop.
Again I must state that this problem does not exist with any of my other Pentax AF lenses.

05-13-2009, 10:31 AM   #9
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Download one of the widely available focus test charts, read the instructions *carefully* and follow them, shoot the tests, and post the results. I know you say you did static tests, but if they weren't legitimate focus test charts with completely unambiguous focusing targets, they probably aren't worth posting. It is far easier to screw up a focus test than to get it right unless you are very experienced at performing focus tests and really understand the issues well.

My guess is that is is exactly as other have been saying - the lens is fine, but the camera just happened to choose focus on the background instead of your target. That's the only thing that could possibly explain a discrepancy of several *meters* in focus. Just because you used center focus point doesn't mean there isn't wiggle room for the AF system - the center "point" is actually a very broad area that would easily include some of the background when shooting in most sports settings with a 105mm (maximum) lens. Especially when your intended target is moving and the background is staying still, it is actually not surprising at all that the camera would choose the background as the easier target to get a lock on.

Now, it might also be that there is a *slight* BF issue - discrepancies on the order of a few millimeters, maybe a centimeter or two - that your controlled focus tests will show. But there is no way that's explaining what happened with the wrestlers. That is pretty much "obviously" a case of the the camera choosing to focus on the background. Unless you controlled focus test also shows a discrepancy of several meters.

Last edited by Marc Sabatella; 05-13-2009 at 10:36 AM.
05-13-2009, 10:53 AM   #10
Pentaxian
seacapt's Avatar

Join Date: Nov 2008
Location: North Carolina , USA
Photos: Gallery
Posts: 2,252
Original Poster
Marc thanks for the sugestion .I guess I should take a more scientifc aproach. My static tests were done with a series of bottles (yeah beer) set on a table at increments of 3 inches on center at a 45 degree agle , not very precise.
I'm not trying to prove anything or slander the product . I'm more upset about the way my issue was handled especially the comment that I should only buy/ use digital lenses than I am about the probabillity of having a bad lens. If I get a chance to set it up with focusing charts in the next couple days , I will post results. Thanks.
Oh Yeah , it was martial arts not wrestling , my kids and I have studied for years.
05-13-2009, 11:13 AM   #11
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
one thing I would like clarified is that there seems to be one inconsistency here.

the OP reports shooting a martial arts competition, and the croud is in focus and the dubjects are not, yet later he states that everything 12 inches behind the subjects is in focus.

These two observations are quite different.

As for the comment about MF being hit or mis, I have to agree, most AF lenses have very little rotation between min focus and infinity, making fine adjustment difficult. lack of a split image also does not help in focusing either
05-13-2009, 12:48 PM   #12
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,145
SeaCapt - I am on your side of the arena in this "discussion". If you have a bunch of lenses, and all of them focus just fine except that one lens, and this you have stated, then Pentax is full of bovine exhaust.

Even if YOU were full of bovine exhaust, there is no need for a company representative to be that rude.
05-13-2009, 06:12 PM   #13
Veteran Member
res3567's Avatar

Join Date: Sep 2008
Location: Houston Tx.
Photos: Gallery
Posts: 1,876
QuoteOriginally posted by stevebrot Quote
All sarcasm aside, the most likely explanation is that the camera locked on the crowd rather than the intended subject. That is one of the main issues I have with AF. You are never really sure what the camera is focusing on. You might want to try locking the AF point at the center spot.

Steve
QuoteOriginally posted by Mike Cash Quote
For the record, I wasn't being sarcastic anywhere in my post. My initial question was a serious one. I practically never use AF lenses so this whole front/back focus thing is Greek to me. But since it doesn't seem likely they designed a focus adjustment range of several meters into the K20D I had to surmise that the proplem was lack of attention to what the camera was focusing on and failure to adjust settings accordingly.
That post was not referring to you, Mr. Cash IMHO.
05-13-2009, 06:51 PM   #14
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
QuoteOriginally posted by res3567 Quote
That post was not referring to you, Mr. Cash IMHO.
I didn't really think it was, but since in other places on the net I have a reputation for being a sarcastic prick I thought it best to be on the safe side and clarify preemptively. I've ticked off a lot of people without even trying to.
05-13-2009, 07:16 PM   #15
Veteran Member
figmental1978's Avatar

Join Date: Feb 2007
Location: Melbourne
Posts: 789
f/3.2 isn't the fastest lens for indoor work and that's only for 28mm end, at 105mm it's f/4.5 I think. I used to have this lens and outdoors it's great but I wouldn't recommend it for indoors. I also agree with Steve, I recently calibrated a back focusing lens and it's spot on now and I also agree with Mike and manual lenses, especially indoors.
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!
cameras, fa, film, focus, frame, k-mount, lens, lenses, pentax, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nature Don't Feck With Me! donallison13 Post Your Photos! 1 11-02-2010 09:10 PM
Nature Don't Feck With Me! donallison13 Post Your Photos! 1 11-02-2010 06:27 PM
HI,I'm Don Dryer d-dryer Welcomes and Introductions 3 11-10-2009 07:47 PM
Don Neal donneal Welcomes and Introductions 2 01-25-2009 05:10 PM
Don in Louisville craftsmansky Welcomes and Introductions 3 10-28-2007 04:21 AM



All times are GMT -7. The time now is 02:57 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