Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-30-2011, 09:34 PM   #181
Veteran Member




Join Date: Jan 2007
Location: Northern California
Posts: 475
QuoteOriginally posted by Smeggypants Quote
Here's the LensAlign I made .... thanks to xbow for the graphics.

Now I've noticed a strange behaviour with my replacement K-5. I put my sigma 30/1.4 on it and it focussed spot on in daylight without any AF fine tuning. Cool! - it also focussed spot on at EV2 ( most of the time ) - Also cool.

today, after making the SmegAlign I decided to calibrate my lenses. I put my FA50/1.4 on and that needed no adjustment either. Cool!

I then put another lens on which did need some adjustment. so after turning on AF adjustment and calibrating this lens, I then put the Sigma 30/1.4 back on and it was really back focussing. It needed a +5 to calibrated it again. The same happened with the FA50/1.4 which needed -10 to calibrate it.

A bit flabbergasted by this I reset the AF fine tuning and turned it off. Both the Sigma 30/1.4 and the FA 50/1.5 showed back focus and front focus respectively and the need the +5 and -10 to correct them


So it seems that simply turning the AF Fine tuning on does something permanent to the AF system, which even a reset won't cure.

I'm taking delivery of my 2nd K-5 tomorrow so I'll be sure to test this again with the new camera.

note: this was all in daylight and was nothing to do with any front focussing in low light. In fact the front focussing behaviour with the replacement K-5 is working fine ( most of the time ) with the sigma in daylight and EV2. AFing with 103 in low light is still inconsistent.
Hi Smeggy,

I noticed a similar oddness when setting the K5 up for AF adjust for the first time.

I reset all and the set them again and things were better, but it still does some inexplicable things now and again.

My thought was that setting an AF adjust initializes a table and a program loop that isn't in the program flow with a camera that has never had any AF adjust done. This is the only thing that sort of fits the behavior I saw and you describe, but it is just a guess and doesn't matter anyway as we cannot do anything about it.

You did the reset, so try setting each lens again afterwards if you have not yet done so.

Good luck.

Ray

03-30-2011, 09:47 PM   #182
Veteran Member




Join Date: Jan 2007
Location: Northern California
Posts: 475
QuoteOriginally posted by Tommot1965 Quote
Ive never heard of those terms before, thanks for bringing it to my attentions,

after a quick google with results at this very forum..it turns out that the lens is a varifocal design.... obviously the aussies aint got a clue about what they are selling!!, as the ets I was told to do.. wouldst work, and shouldn't work

great forum , many thanks for the very helpful advice
Hi Tommo,

I think a Google search will show that this lens is notorious for focusing issues across many brands with FF on the wide end being common.

In addition, even very good zoom lenses will not hold perfect focus at all focal lengths. It is also usually not going to give good results on most any zoom to focus at one setting and zoom to another without a re-focus at the new focal length, but you probably already know this.

I adjust my zooms one of two ways:

Best focus where I use it the most.

Best focus at the longest focal setting as the wide end will be more forgiving of a focus error.

BTW, I have a Sigma 18-50 f2.8 that isn't a bad little lens, but it REALLY doesn't want to focus properly on the K5. It was always ok on my K10 and K20. This makes me wonder about what data the camera is reading from the lens chip and if the Sigma lenses need an update for the K5?

Sigma is pretty good about re-calibrating and re-chipping products if needed, so it might be worthwhile to contact them about the lens.

Alternately, you could just buy a DA* 16-50....

Ray
03-30-2011, 11:41 PM   #183
Veteran Member
Tommot1965's Avatar

Join Date: Sep 2010
Location: Perth Western Australia
Photos: Gallery | Albums
Posts: 1,026
QuoteOriginally posted by Ray Pulley Quote
Hi Tommo,

I think a Google search will show that this lens is notorious for focusing issues across many brands with FF on the wide end being common.

In addition, even very good zoom lenses will not hold perfect focus at all focal lengths. It is also usually not going to give good results on most any zoom to focus at one setting and zoom to another without a re-focus at the new focal length, but you probably already know this.

I adjust my zooms one of two ways:

Best focus where I use it the most.

Best focus at the longest focal setting as the wide end will be more forgiving of a focus error.

BTW, I have a Sigma 18-50 f2.8 that isn't a bad little lens, but it REALLY doesn't want to focus properly on the K5. It was always ok on my K10 and K20. This makes me wonder about what data the camera is reading from the lens chip and if the Sigma lenses need an update for the K5?

Sigma is pretty good about re-calibrating and re-chipping products if needed, so it might be worthwhile to contact them about the lens.

Alternately, you could just buy a DA* 16-50....

Ray
Ray

thanks a lot for that post mate...

I did do some googling about the problems that lens has..I didn't get any results..but Ill have another look....

the problem its so inconsistent it aint funny...if I focus at 17 mm Ill get a good enough result. if I then zoom to 50mm, refocus, then back to 17 mm, yet another refocus 3 outta 4 are OOF...its doing me bleedin head in to be sure...

contrast AF is still giving me better/ consistent results with this lens..!
03-31-2011, 02:10 AM   #184
Veteran Member




Join Date: Jan 2009
Location: Budapest
Posts: 821
Tommot, just have your lens calibrated by Sigma service (they'll need you cam too since they'll calibrate the lens to your body). As Ray wrote, this (different focus error at wide and tele end) is quite common with some Sigma lenses. The local Nikon guys always advise to visit the Sigma repair center for calibration right after purchasing the lens

By the way, my DA17-70 and 16-50 also exhibit this to some extent: when shooting things farther than 3-5 meter away (e.g. cityscapes, landscapes, etc) with focal length under approx 20mm the cam (both K-m and K-5) usually doesn't get perfect focus, it's slightly off. Not evident in screen size, but you can see it in 100% pixel peeping. Since these are parfocal lenses (as practically all IF lenses are), I just turn the zoom ring to the middle range (or to the tele end), lock focus, then zoom back to wide end and take the picture. This gives perfect focus even when pixel peeping I guess wide fov making objects quite small and Pentax's oversized AF sensors might be the culprit.

03-31-2011, 02:21 AM   #185
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by Smeggypants Quote
I will try, but my priority is taking real life photographs rather than exact scientific study
Understood. It would just be useful to see how the K-5 compares to the K20D. I really don't know whether V1.03 made it catch up or not.

QuoteOriginally posted by Smeggypants Quote
Frankly for real life analysis such accuracy isn't needed.
Why did you built the SmegAlign then?
What was wrong with the flat charts if you are not too fussed about accuracy?

Frankly, I believe a cheap print of a regular focus chart is safer to use than an XYZ-Align which might be misaligned itself (Ray Pulley's seemed a bit out of shape in his shots) and to which the camera is not exactly aligned to. An XYZ-Align holds the promise of a more precise adjustment but only if the setup is done with great care.
03-31-2011, 02:59 AM   #186
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by simico Quote
As Ray wrote, this (different focus error at wide and tele end) is quite common with some Sigma lenses.
Was the Pentax service centre wrong when it said
...there was nothing wrong with the lens (Pentax 16-50), it is common for most wide angle zooms to mis-focus at the wide end.
?

QuoteOriginally posted by simico Quote
Since these are parfocal lenses (as practically all IF lenses are), ...
Are you sure there is a relationship? My Tamron 18-250 is has IF and is not parfocal. Parfocal zooms are more expensive to build than varifocal lenses because they need a compensator group. I understand that most modern AF lenses are not parfocal. The Pentax 16-45, e.g., is not. Richard Day lists some more which are not. Some claim the 16-50 is not parfocal.

Maybe some varifocal lenses do not produce huge focus offsets, but I wonder why any manufacturer would make the expense to make a lens parfocal if it doesn't need to be. Video lenses need to be parfocal and MF lenses hugely benefit from being parfocal but AF lenses don't really depend on being parfocal.
03-31-2011, 04:45 AM   #187
Veteran Member
Tommot1965's Avatar

Join Date: Sep 2010
Location: Perth Western Australia
Photos: Gallery | Albums
Posts: 1,026
QuoteOriginally posted by simico Quote
Tommot, just have your lens calibrated by Sigma service (they'll need you cam too since they'll calibrate the lens to your body). As Ray wrote, this (different focus error at wide and tele end) is quite common with some Sigma lenses. The local Nikon guys always advise to visit the Sigma repair center for calibration right after purchasing the lens

By the way, my DA17-70 and 16-50 also exhibit this to some extent: when shooting things farther than 3-5 meter away (e.g. cityscapes, landscapes, etc) with focal length under approx 20mm the cam (both K-m and K-5) usually doesn't get perfect focus, it's slightly off. Not evident in screen size, but you can see it in 100% pixel peeping. Since these are parfocal lenses (as practically all IF lenses are), I just turn the zoom ring to the middle range (or to the tele end), lock focus, then zoom back to wide end and take the picture. This gives perfect focus even when pixel peeping I guess wide fov making objects quite small and Pentax's oversized AF sensors might be the culprit.

yep Im gonna do that...they have to send it to sydney...be away for 10 days they reckon..I might send my 70-200 sigma with it too, as that has alway been soft at F2.8..perhaps a calibration will help that too ?

by the way...does anyone know whats done during these calibration ..is it a mechanical job or just electronic fixing ?
03-31-2011, 09:05 AM   #188
Veteran Member
Smeggypants's Avatar

Join Date: Sep 2010
Posts: 1,536
Original Poster
QuoteOriginally posted by Class A Quote
Understood. It would just be useful to see how the K-5 compares to the K20D. I really don't know whether V1.03 made it catch up or not.


Why did you built the SmegAlign then?
What was wrong with the flat charts if you are not too fussed about accuracy?

Frankly, I believe a cheap print of a regular focus chart is safer to use than an XYZ-Align which might be misaligned itself (Ray Pulley's seemed a bit out of shape in his shots) and to which the camera is not exactly aligned to. An XYZ-Align holds the promise of a more precise adjustment but only if the setup is done with great care.
Because the Smeglaign is easier to mount on a flat surface ( more ergonomic ) and I wanted a little bit more consistency and accuracy than just chucking a piece of A4 paper around.

Anyway .... 2nd K-5 has arrived, so I'm going tocheck that out .....

03-31-2011, 01:31 PM   #189
Ash
Community Manager
Loyal Site Supporter
Ash's Avatar

Join Date: Mar 2007
Location: Toowoomba, Queensland
Photos: Gallery | Albums
Posts: 22,678
QuoteOriginally posted by Tommot1965 Quote
yep Im gonna do that...they have to send it to sydney...be away for 10 days they reckon..I might send my 70-200 sigma with it too, as that has alway been soft at F2.8..perhaps a calibration will help that too ?

by the way...does anyone know whats done during these calibration ..is it a mechanical job or just electronic fixing ?
Tommo, is your 70-200 softness an expected softness as per my experience with it here? Or is it decentered or unusually soft? And is it soft on all the cameras you've used or just the K-5?
03-31-2011, 07:26 PM   #190
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by Smeggypants Quote
Because the Smeglaign is easier to mount on a flat surface ( more ergonomic ) and I wanted a little bit more consistency and accuracy than just chucking a piece of A4 paper around.
I doubt that you have achieved more consistency and accuracy if you are not including a careful alignment of the SmegAlign to the camera. Believe it or not, chucking a piece of A4 paper around is more forgiving regarding perfect alignment.
03-31-2011, 07:28 PM   #191
Veteran Member
Tommot1965's Avatar

Join Date: Sep 2010
Location: Perth Western Australia
Photos: Gallery | Albums
Posts: 1,026
Ash
It's always been soft , sharpens up at f4 though
03-31-2011, 07:41 PM   #192
Veteran Member
Smeggypants's Avatar

Join Date: Sep 2010
Posts: 1,536
Original Poster
QuoteOriginally posted by Class A Quote
I doubt that you have achieved more consistency and accuracy if you are not including a careful alignment of the SmegAlign to the camera. Believe it or not, chucking a piece of A4 paper around is more forgiving regarding perfect alignment.
Actually after a couple of hours of mass calibrating today . I tried both the SmegAlign, A4 focus sheet and actually taking pics of real world stuff, I found the real world stuff was the best in calibrating the lenses.

So I'm glad I didn't poop a 100 shekels on a real LensAlign, adn as the SmegAlign took half an hour to build with a chop saw, a few scraps of MDF, etc all in all a good learning experience.

Which also proves all those popping on my initial tests in the OP of this thread wrong. Cripes some people even started getting into field curvature!!! Talk about OCD

I'm happy. I have two new K-5s which focus accurately with all my lenses down to EV2 and below. The next step is to get out there and take pics.

03-31-2011, 08:28 PM   #193
Veteran Member




Join Date: Jan 2007
Location: Northern California
Posts: 475
QuoteOriginally posted by Tommot1965 Quote
Ash
It's always been soft , sharpens up at f4 though
Tommo,

There are many versions of this lens, but I have one (f2.8) and it isn't very sharp wide open.

It is pretty good stopped down a bit though.

Of course, if I had my druthers (whatever a druther is), I would have the legendary FA 80-200 f2.8.

I swear that it seems like I have been drooling over that lens for so long that bell bottoms and tie-dye have come and gone twice in the meantime...

Ray
03-31-2011, 08:39 PM   #194
Ash
Community Manager
Loyal Site Supporter
Ash's Avatar

Join Date: Mar 2007
Location: Toowoomba, Queensland
Photos: Gallery | Albums
Posts: 22,678
QuoteOriginally posted by Tommot1965 Quote
Ash
It's always been soft , sharpens up at f4 though
Mate, that'd be the inherent softness of the lens by design.
My own copy was not sharp until f/5.6, and even then it was not sharp throughout the frame.
So I'm afraid if you're looking for better performance, the Tamron 70-200 and Pentax 80-200 may be able to offer this. Otherwise it'll have to be fast telephoto primes.
03-31-2011, 09:10 PM   #195
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by Smeggypants Quote
Actually after a couple of hours of mass calibrating today . I tried both the SmegAlign, A4 focus sheet and actually taking pics of real world stuff, I found the real world stuff was the best in calibrating the lenses.
How did the A4 focus chart compare to the SmegAlign?
BTW, using "real world stuff" is what I did for my own calibration and I've been very happy with my results since then.

QuoteOriginally posted by Smeggypants Quote
Which also proves all those popping on my initial tests in the OP of this thread wrong.
Your notion of "proof" and my notion of "proof" are very different.

QuoteOriginally posted by Smeggypants Quote
I'm happy. I have two new K-5s which focus accurately with all my lenses down to EV2 and below.
Doesn't the "inconsistency" issue you reported bother you?
If a K-5 only gives me 7 out of 10 shots in focus independently of light levels, I'd be downgrading if I exchanged my K100D with a K-5.
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!
camera, dslr, k-5, k-5 ii, k-5 iis, k20d, k5, lens, light, pentax k-5, sigma, test, tungsten
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K20D versus K10D Mapleleaf-Mick Pentax DSLR Discussion 13 12-24-2010 10:58 AM
gx20 versus k20d! kositoes Pentax DSLR Discussion 22 09-25-2009 03:00 PM
Tests to determine if a new K20D is faulty eman Pentax DSLR Discussion 21 07-05-2008 10:30 PM
gx-20 versus k20d anyone? davieFL Photographic Technique 1 06-18-2008 12:23 PM
Some K20D Vs K10D ISO noise tests (100 to 6400) RiceHigh Pentax DSLR Discussion 15 02-25-2008 04:00 PM



All times are GMT -7. The time now is 03:39 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