K-01 and K5-II Contrast AF problems

Started May 5, 2013 | Discussions
philzucker
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K-01 and K5-II Contrast AF problems
May 5, 2013

Yesterday my K-01 arrived, and of course I went around trying it out. More about that later ...

I was quite thrilled with the first results, but I also noticed some softness using my Tamron 18-250 at its long end and started some testing today. During those tests I switched from the 18-250 to my Tamron 70-200/2.8 to do the testing with a better quality lens and then also included my K5-II body. I used a tripod and a wireless remote, of course, ISO 100 and Av mode. The results were more or less the same and - IMO - somewhat disconcerting:

- Contrast AF didn't work well with either the 18-250@250mm or the 70-200@200mm. I tried a variety of subjects with different amounts of contrast with more or less the same results.

- manual AF on the K-01 and PD-AF on the K5-II worked flawlessly and accurate ...

Here one of the many example I shot that demonstrate my findings best - all samples imported in LR 4.4, cropped and slightly exposure adjusted, no other modifications - and of course these are 100% crops if you see them at original size. What you're looking it is a newspaper pinned to a garden shed positioned around 10 meters from the camera:

K-01 with Tamron 70-200@200mm, Contrast AF

K-01, same lens, manual focus - focus peaking used

K5-II, same lens, Contrast AF

K5-II, same lens, phase detection AF

I had more or less the same results with the Tamron 18-250@250mm - flawless focus on the K5-II with PD-AF, out of focus pictures using Contrast-AF on both bodies.

Have to add that I also tested with other lenses. For example with the FA35/2.0 - hadn't too many problems with it at varying distances. In one setup I found some very slight front focusing with the K5-II and PD-AF, perfect focus with K5-II and Contrast AF and slight back focusing with the K-01's Contrast AF, but I can live with all that.

What bugs me is the inability of both bodies to focus correctly with Contrast AF using my two telephoto lenses at its long ends ... What is happening here? What am I doing wrong? Or what are the bodies doing wrong? Am I expecting too much out of Contrast AF? Has anybody had comparable experiences?

Have to stress again that I did the testing with lots of different subjects at different distances and that I do sincerely hope that I was careful enough to rule out user errors (like tripod shake etc.). As I used the wireless remote sensor stabilization was automatically turned off with both bodies. And I took multiple shots too. So these results should really be valid ...

Any thoughts and help on this much appreciated!

Phil

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philzucker
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... a second example (K5-II only)
In reply to philzucker, May 5, 2013

... two shots taken with the K5-II - 100% crops again, focus was on the rightmost object (was in the center before the crop). Lens used Tamron 70-200/2.8@160mm. Object distance: pretty near, only about 2 meters.

1. Spot on focus with PD-AF:

PD-AF on rightmost object

2. Front focusing using Contrast AF:

Contrast AF on rightmost object

I'm somewhat mystified ...

Phil

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brandrx
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

Hi Phil,

Unfortunately some lenses just don't work worth a damn using CDAF. For instance: My Sigma 50-500mm APO HSM OS at 500mm trying to focus on a subject that is greater than 150 feet will indicate focus lock if I am coming from a setting that is less than 150 feet on the lens to start with but the resultant image is very OOF. If I start my focusing with the lens set to infinity then it will lock focus on the subject that is greater than 150 feet and it will be sharp.

From what little information I have been able to gather so far, it seems the problem is more common with Tamron and Sigma lenses than with Pentax lenses.

Good luck.

Ron

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philzucker
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Re: K-01 and K5-II Contrast AF problems
In reply to brandrx, May 5, 2013

brandrx wrote:

Hi Phil,

Unfortunately some lenses just don't work worth a damn using CDAF. For instance: My Sigma 50-500mm APO HSM OS at 500mm trying to focus on a subject that is greater than 150 feet will indicate focus lock if I am coming from a setting that is less than 150 feet on the lens to start with but the resultant image is very OOF. If I start my focusing with the lens set to infinity then it will lock focus on the subject that is greater than 150 feet and it will be sharp.

From what little information I have been able to gather so far, it seems the problem is more common with Tamron and Sigma lenses than with Pentax lenses.

Darn, you seem to be right, Ron. Grabbed the DA50-200 I gave my daughter as a present (because I didn't use it anymore), and did some quick handheld shots @200mm with it on my K-01 - using the same targets. No visible AF problems here ... A shame that the Tammys have problems with CD-AF.

Oh well, I planned to get the DA50-200 WR anyway ... or the DA55-300. Will have to do so now sooner then planned.

Thanks for your quick reply, Ron!

Phil

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philzucker
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Re: ... a second example (K5-II only)
In reply to philzucker, May 5, 2013

2. Front focusing using Contrast AF:

... it's actually back focusing, sorry ...

Contrast AF on rightmost object

Phil

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brandrx
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...also
In reply to brandrx, May 5, 2013

brandrx wrote:

Hi Phil,

Unfortunately some lenses just don't work worth a damn using CDAF. For instance: My Sigma 50-500mm APO HSM OS at 500mm trying to focus on a subject that is greater than 150 feet will indicate focus lock if I am coming from a setting that is less than 150 feet on the lens to start with but the resultant image is very OOF. If I start my focusing with the lens set to infinity then it will lock focus on the subject that is greater than 150 feet and it will be sharp.

From what little information I have been able to gather so far, it seems the problem is more common with Tamron and Sigma lenses than with Pentax lenses.

BTW: Pentax has made some firmware updates for the K-5 II (Ver 1.02) and K-01 (Ver 1.02) that "Optimized contrast AF when using [HD PENTAX-DA 560mmF5.6ED AW] lens". I have no idea if these firmware updates helped with CDAF of other lenses or not. I do know that I have updated my K-01 firmware to Ver 1.03 and I still have the same problem with my Sigma 50-500mm APO HSM OS lens.

Cheers.

Ron

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MightyMike
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

I've been saying this for months... CDAF isn't the second coming of focusing systems, some lenses just don't work

Sigma 18-125mm F3.5-5.6, Sigma 75-200mm F3.8, Sigma 17-70mm F2.8-4.0, and others, the common issue is it gets worse at the tele end.

The issues is likely spherical aberrations, all lenses have this to some extent, this causes softening of the image if its really bad and allows for 3 points of focus, of course 2 of those points aren't accurate and one is best focus. What happens is the stupid CDAF system doesn't know which best focus to stop at and just lands on one. there may be a way the CDAF system can be programmed to go past the first point of focus to the best point of focus and this may be occurring in first party lenses.

So for all those people who are singing the praises of CDAF being the most accurate system out their, look again, with some lenses and in low light its a dud! its useless!

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Kerusker
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

Phil,

some time ago I observed a similar behavior with a SIGMA Zoom at the long end i.e. PD-AF is spot on and CD-AF is off in almost every shot.  I tried to get some info from Pentax but they blamed Sigma (of course).

There are at least three possible reasons:

A) The contrast of the lens is too low for contrast detection by the CD-AF system.

B) Lens aberration like CA, field curvature etc. are too high for CD-AF.

C) The CD-AF algorithm has to go past the focus plane and it may use a return value R to return to the distance of optimal contrast. Some lenses may not be able to return correctly or the value R may be wrong.

Case C) is most likely to me but I don't have enough information (or experience) to be sure.

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brandrx
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Re: K-01 and K5-II Contrast AF problems
In reply to MightyMike, May 5, 2013

MightyMike wrote:

I've been saying this for months... CDAF isn't the second coming of focusing systems, some lenses just don't work

Sigma 18-125mm F3.5-5.6, Sigma 75-200mm F3.8, Sigma 17-70mm F2.8-4.0, and others, the common issue is it gets worse at the tele end.

The issues is likely spherical aberrations, all lenses have this to some extent, this causes softening of the image if its really bad and allows for 3 points of focus, of course 2 of those points aren't accurate and one is best focus. What happens is the stupid CDAF system doesn't know which best focus to stop at and just lands on one. there may be a way the CDAF system can be programmed to go past the first point of focus to the best point of focus and this may be occurring in first party lenses.

So for all those people who are singing the praises of CDAF being the most accurate system out their, look again, with some lenses and in low light its a dud! its useless!

I agree with Mike when it comes to CDAF with some lenses. However, I did find that my new Sigma 18-250mm HSM Macro seems to be working fine with my K-01. I just now stepped outside and took a few quick shots using the K-01 + Sigma 18-250mm HSM Macro and with the lens at 250mm. I shot at subjects at different distances and all seemed to be in focus.

The K-01 with manual focusing and focus peaking is a dream come true IMO.

Ron

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flektogon
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

This is really weird as from my experience each of my lenses focus perfectly when using the CDAF method. But using the PDAF is something else. For example, my DA 16-45 perfectly focuses (CDAF) at any focal length setting, but when using the (standard) PDAF, in the short focal distances it completely missfocuses. Always it tends to focus farther than it should.

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philzucker
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Re: ...also
In reply to brandrx, May 5, 2013

brandrx wrote:

brandrx wrote:

Hi Phil,

Unfortunately some lenses just don't work worth a damn using CDAF. For instance: My Sigma 50-500mm APO HSM OS at 500mm trying to focus on a subject that is greater than 150 feet will indicate focus lock if I am coming from a setting that is less than 150 feet on the lens to start with but the resultant image is very OOF. If I start my focusing with the lens set to infinity then it will lock focus on the subject that is greater than 150 feet and it will be sharp.

From what little information I have been able to gather so far, it seems the problem is more common with Tamron and Sigma lenses than with Pentax lenses.

BTW: Pentax has made some firmware updates for the K-5 II (Ver 1.02) and K-01 (Ver 1.02) that "Optimized contrast AF when using [HD PENTAX-DA 560mmF5.6ED AW] lens". I have no idea if these firmware updates helped with CDAF of other lenses or not. I do know that I have updated my K-01 firmware to Ver 1.03 and I still have the same problem with my Sigma 50-500mm APO HSM OS lens.

Thanks for the additional info, Ron.

But both bodies hat the latest firmware installed.

The K-01 shipped with 1.00, BTW. Must have had a long stay on that shelf it came from ...

Phil

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philzucker
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Re: K-01 and K5-II Contrast AF problems
In reply to MightyMike, May 5, 2013

MightyMike wrote:

I've been saying this for months... CDAF isn't the second coming of focusing systems, some lenses just don't work

Sigma 18-125mm F3.5-5.6, Sigma 75-200mm F3.8, Sigma 17-70mm F2.8-4.0, and others, the common issue is it gets worse at the tele end.

If my findings are correct add Tamron 18-250 f3.5-6.3 and Tamron 70-200 f2.8 to that list ... and yes, it's worse at the tele end with those two too ...

The issues is likely spherical aberrations, all lenses have this to some extent, this causes softening of the image if its really bad and allows for 3 points of focus, of course 2 of those points aren't accurate and one is best focus. What happens is the stupid CDAF system doesn't know which best focus to stop at and just lands on one. there may be a way the CDAF system can be programmed to go past the first point of focus to the best point of focus and this may be occurring in first party lenses.

Hmm, at least with the 70-200/f2.8 it's hard to for me to believe that severe aberrations are the problem here ... it's a very fine lens even wide open ... but of course I don't know for sure.

So for all those people who are singing the praises of CDAF being the most accurate system out their, look again, with some lenses and in low light its a dud! its useless!

Then again with other lenses and in good light it does have it's use, doesn't it?

Thanks for your info, Mike!

Phil

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philzucker
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Re: K-01 and K5-II Contrast AF problems
In reply to Kerusker, May 5, 2013

Kerusker wrote:

Phil,

some time ago I observed a similar behavior with a SIGMA Zoom at the long end i.e. PD-AF is spot on and CD-AF is off in almost every shot.  I tried to get some info from Pentax but they blamed Sigma (of course).

There are at least three possible reasons:

A) The contrast of the lens is too low for contrast detection by the CD-AF system.

B) Lens aberration like CA, field curvature etc. are too high for CD-AF.

C) The CD-AF algorithm has to go past the focus plane and it may use a return value R to return to the distance of optimal contrast. Some lenses may not be able to return correctly or the value R may be wrong.

Case C) is most likely to me but I don't have enough information (or experience) to be sure.

As I already said in my answer to Mike, I don't think inferior contrast or to severe aberrations are real issues with the Tamron 70-200/2.8. So I'd also settle for "C", whatever it means!

Phil

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philzucker
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Re: K-01 and K5-II Contrast AF problems
In reply to flektogon, May 5, 2013

flektogon wrote:

This is really weird as from my experience each of my lenses focus perfectly when using the CDAF method. But using the PDAF is something else. For example, my DA 16-45 perfectly focuses (CDAF) at any focal length setting, but when using the (standard) PDAF, in the short focal distances it completely missfocuses. Always it tends to focus farther than it should.

Ah, well, different lenses, different problems, I guess. Did a quick check with my DA16-45@16mm on my K5-II and well yes, some (if very slight) backfocus with PD-AF, and accurate focus with CD-AF.

But PD-AF is adjustable - I just did a +3 AF fine adjustment for the DA16-45 and now it seems to focus very exact. CD-AF problems are less easy to fix unfortunately ...

Do you have lenses that are comparable to mine (3rd-party ones) who work flawlessly with CD-AF in the 200-250mm range? Would be interesting to know ...

Phil

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flektogon
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

philzucker wrote:

flektogon wrote:

This is really weird as from my experience each of my lenses focus perfectly when using the CDAF method. But using the PDAF is something else. For example, my DA 16-45 perfectly focuses (CDAF) at any focal length setting, but when using the (standard) PDAF, in the short focal distances it completely missfocuses. Always it tends to focus farther than it should.

Ah, well, different lenses, different problems, I guess. Did a quick check with my DA16-45@16mm on my K5-II and well yes, some (if very slight) backfocus with PD-AF, and accurate focus with CD-AF.

But PD-AF is adjustable - I just did a +3 AF fine adjustment for the DA16-45 and now it seems to focus very exact. CD-AF problems are less easy to fix unfortunately ...

Do you have lenses that are comparable to mine (3rd-party ones) who work flawlessly with CD-AF in the 200-250mm range? Would be interesting to know ...

Phil

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Unfortunately I do not have any 3-rd party lens, but my, the only “long focal length” lens, the Pentax A 70-210/4 perfectly focuses i.e. there is a perfect match between the actual and the AF detected focus distance. In my opinion the problematic are only wide angle lenses, when the phase detection somehow gives a false information to the AF system. All my lenses above around 30-35mm of the focal length seem to be working properly. But the CDAF works for all of them without any problem.

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MightyMike
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

philzucker wrote:

MightyMike wrote:

I've been saying this for months... CDAF isn't the second coming of focusing systems, some lenses just don't work

Sigma 18-125mm F3.5-5.6, Sigma 75-200mm F3.8, Sigma 17-70mm F2.8-4.0, and others, the common issue is it gets worse at the tele end.

If my findings are correct add Tamron 18-250 f3.5-6.3 and Tamron 70-200 f2.8 to that list ... and yes, it's worse at the tele end with those two too ...

Yes my findings are that its always worse at the long end, also it always seems to be front focus

The issues is likely spherical aberrations, all lenses have this to some extent, this causes softening of the image if its really bad and allows for 3 points of focus, of course 2 of those points aren't accurate and one is best focus. What happens is the stupid CDAF system doesn't know which best focus to stop at and just lands on one. there may be a way the CDAF system can be programmed to go past the first point of focus to the best point of focus and this may be occurring in first party lenses.

Hmm, at least with the 70-200/f2.8 it's hard to for me to believe that severe aberrations are the problem here ... it's a very fine lens even wide open ... but of course I don't know for sure.

Spherical aberrations are such that they don't necessarily have a visible affect on image quality, yes bad ones will, however its more of a pattern, you could have poorly corrected SA can lead to focus shift even with PDAF, its still corrected and you can still get great IQ but there is still a difference between 2 inaccurate focus points and the point of best focus. Take for instance the focus shift described on the Samyang 85mm F1.4, below F4 you need to focus wide open, above F4 there is a notable shift and focusing wide open won't necessarily provide accurate focus stopped down, this is all due to SA despite it being a very well regarded lens.

So for all those people who are singing the praises of CDAF being the most accurate system out their, look again, with some lenses and in low light its a dud! its useless!

Then again with other lenses and in good light it does have it's use, doesn't it?

I suppose there are some uses for CDAF, but until its vastly improved i'll stick with my PDAF... on another note the K-5IIs PDAF focuses far far better in low light then the CDAF, according to Pentax the PDAF has a 4 stop advantage over the CDAF

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Mike from Canada
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MightyMike
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013
Do you have lenses that are comparable to mine (3rd-party ones) who work flawlessly with CD-AF in the 200-250mm range? Would be interesting to know ...

I'd like to point out that the Pentax F 70-210m F4-5.6 and IIRC the 55-300 work fine in CDAF

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Mike from Canada
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brandrx
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

philzucker wrote:

flektogon wrote:

This is really weird as from my experience each of my lenses focus perfectly when using the CDAF method. But using the PDAF is something else. For example, my DA 16-45 perfectly focuses (CDAF) at any focal length setting, but when using the (standard) PDAF, in the short focal distances it completely missfocuses. Always it tends to focus farther than it should.

Ah, well, different lenses, different problems, I guess. Did a quick check with my DA16-45@16mm on my K5-II and well yes, some (if very slight) backfocus with PD-AF, and accurate focus with CD-AF.

But PD-AF is adjustable - I just did a +3 AF fine adjustment for the DA16-45 and now it seems to focus very exact. CD-AF problems are less easy to fix unfortunately ...

Do you have lenses that are comparable to mine (3rd-party ones) who work flawlessly with CD-AF in the 200-250mm range? Would be interesting to know ...

As I wrote in one of my other replies in this thread, the new Sigma 18-250mm F3.5-6.3 DC Macro HSM works great with the K-01's CDAF. Note: As I am writing this I am also checking out catch-in-focusing against some hummingbirds with the K-5 + the Sigma 18-250mm F3.5-6.3 DC Macro HSM.

Cheers.

Ron

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tdwesbo
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Re: K-01 and K5-II Contrast AF problems
In reply to philzucker, May 5, 2013

YMMV, but I've been unable to get reliable CDAF with any non-Pentax lens on my K-5.  Sigma offered to 'fix' my 70-200 so that it would work, but I haven't sent it in yet.

Flawless with my Pentax lenses, however.  It's a little slow with the 18-250, but it gets there.  DA40 is VERY fast in CDAF on my K-5.  It can hunt with my FA100 macro but will eventually find very sharp focus.

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philzucker
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Re: K-01 and K5-II Contrast AF problems
In reply to brandrx, May 5, 2013

brandrx wrote:

As I wrote in one of my other replies in this thread, the new Sigma 18-250mm F3.5-6.3 DC Macro HSM works great with the K-01's CDAF. Note: As I am writing this I am also checking out catch-in-focusing against some hummingbirds with the K-5 + the Sigma 18-250mm F3.5-6.3 DC Macro HSM.

Thanks, Ron. Good to know!

Phil

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