Focusing problem with K10D

Started Dec 28, 2006 | Discussions
KSV Veteran Member • Posts: 3,351
Focusing problem with K10D

There was quite a few threads about this topic in resent times. So lets employ our collective brain and try to figure out:

1. In which situations it happens most and in which less. Lets collect statistics. At first glance appears like low-light and in particularly incandescent light make more trouble then anything else.

2. How do you battle this. Manual focus could be solution. Some said that centre focusing spot not as reliable as corner one. Some suggest that because hand-held camera actually moves between focus lock and shutter release enough to be out of focus. Anything else?

Lets share our observations, collect statistics and hopefully we figure out what to do to battle this.
Cheers.

PS. Those who believe that they do not have any focus issue could help also by sharing what lenses and under which conditions they using.

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HerbChong Senior Member • Posts: 1,369
Re: Focusing problem with K10D

the DA 21 on my K10D just doesn't sometimes and at other times it does in identical lighting conditions, usually just a few seconds later. i can be pointed at a sharp high contrast edge and it just won't focus. point to a low contrast edge right beside it and it focuses no problem. i have occasionally had the same thing happen on my FA 31. almost all of the time, i am locked to the center focus point, so there is no issue about the camera trying to decide which focus point to use.

i think it is a body calibration problem and bodies that have AF problems need to be calibrated by a service center. there may be a firmware problem in AF, but i tend to doubt it. i doubt the lens being a problem at all because all of these lenses work reliably on my *istD.

Herb...

OP KSV Veteran Member • Posts: 3,351
Ok, if it is calibration problem,

then it should give you constant front/back focus regardless what lens ou using. Is this the case?

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dvse New Member • Posts: 11
Re: Focusing problem with K10D

I have created a dpreview account specifically to comment on this issue -

The K10D auto focus system seems to have a problem by design, perhaps this is a failing of SAFOX in general as there have been reports for older cameras as well.

It can be argued that this is 'normal' behaviour within error margin for AF - but in this case it is quite uncompetitive with other systems on the market.

I am currently on my third K10d body and they all have behaved the same in this respect:

  • Front focus in tungsten light to the extent that the point of focus

is completely unsharp at apertures f2 and larger, depth of field becomes
sufficiently large to cover this by f5.6.

  • Correct focus under daylight at the largest apertures

  • Slight back focus under fluorescent light (maybe around 6000K?)

This is consistent with all of my 4 lenses - 31mm Limited, 43mm Limited, 50mm f1.4 and 18-55mm, I tested on real life objects as well as the D70 focus chart.

I have also a canon 350D with 50mm f1.8 and 35mm f2 and have not encountered anything similar - there are focusing errors of course but they are not systematic.

Voe
Voe Contributing Member • Posts: 528
Re: Ok, if it is calibration problem,

My FA 77mm Limited back focuses between 2-6mm on the focus chart.
The next one is with FA 77mm Limited
Exposure: 0.005 sec (1/200)
Aperture: f/2
Metering Mode: Spot
Daylight - AutoWB

The DA 16-45mm seems to back focus within 2-6mm but due to the lack of shallow DOF is not that obvious.
This one is with DA 16-45mm
Exposure: 0.008 sec (1/125)
Aperture: f/4
Focal Length: 45 mm
Metering Mode: Spot
Daylight - AutoWB

So I believe mine is to do with proper adjustment of camera auto focus.

I have also tested my M 50mm 1.7 and M 135mm 3.5 and is hard to tell because sometimes it back focuses sometimes it front focuses. The green light confirmation is not always correct.

KSV wrote:

then it should give you constant front/back focus regardless what
lens ou using. Is this the case?

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lak Contributing Member • Posts: 998
Re: Focusing problem with K10D

dvse wrote:

  • Front focus in tungsten light to the extent that the point of focus

is completely unsharp at apertures f2 and larger, depth of field
becomes sufficiently large to cover this by f5.6.

Someone has suggested the possibility of IR sensitivity causing the error in tungsten light. I wonder if anyone has a hot mirror filter to test out this theory?

sunst8 New Member • Posts: 3
Re: Focusing problem with K10D

My first post to get some assistance with K10D focussing problem.

I have been using my FA50mmf1.4 on the K10D and consistently have front focus problems when used in indoor natural light settings.

After 6 days of (frustrated) use I sent the camera back to Pentax.

I received the following email response from a Pentax Rep before the camera had even been checked. Still waiting to get the camera back.

I am interested to know what your thoughts are on Pentax response - are they trying to fob me off.

"There is nothing wrong with your camera or lens.

Please note that Pentax analogue lenses in use with your Pentax digital

camera will not give the same focus performance as Pentax DA lenses which have been specifically designed for digital use.

For best results with your analogue lenses please use lowest aperture
possible.

The above is true for all makes and brands.

You cannot expect perfect edge to edge focus on any digital camera with any analogue lens.

We will arrange for return of your camera and lens after taking the
precaution to check at no charge."

dvse New Member • Posts: 11
Re: Focusing problem with K10D

Yes, I have been thinking about it... Hopefully someone who already has one can test this for us as I would have no other use for it were I to buy.

dvse New Member • Posts: 11
Re: Focusing problem with K10D

This is a somewhat unfortunate position on the behalf of the Pentax representative - the K10D manual does not state anything to this effect, quiet the opposite - all functions are meant to be availabel with FA lenses

Also it is very unlikely that there is a genuine technical reason for DA lenses to behave differently.

Voe
Voe Contributing Member • Posts: 528
Re: Focusing problem with K10D

I went to Pentax Service Center and they told me the same. But come on I did not pay that much money (about $700USD) just to be told this BS.

sunst8 wrote:

My first post to get some assistance with K10D focussing problem.

I have been using my FA50mmf1.4 on the K10D and consistently have
front focus problems when used in indoor natural light settings.

After 6 days of (frustrated) use I sent the camera back to Pentax.

I received the following email response from a Pentax Rep before
the camera had even been checked. Still waiting to get the camera
back.

I am interested to know what your thoughts are on Pentax response -
are they trying to fob me off.

"There is nothing wrong with your camera or lens.

Please note that Pentax analogue lenses in use with your Pentax
digital
camera will not give the same focus performance as Pentax DA
lenses which have been specifically designed for digital use.

For best results with your analogue lenses please use lowest aperture
possible.

The above is true for all makes and brands.

You cannot expect perfect edge to edge focus on any digital camera
with any analogue lens.

We will arrange for return of your camera and lens after taking the
precaution to check at no charge."

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emem
emem Veteran Member • Posts: 4,423
Sounds like typical CR Kennedy bulldust ...

.... When I read that post of yours I thought - " I bet this guy is in Australia, it just sounds so much like CR Kennedy to say something like that." They really are the pits. Don't believe a word of it. They're making excuses for a problem that's just too difficult for them to do anything about.

I sent my Sigma 500 DG Super back to them to be reflashed to suit the K10D. Their first try was that it would cost me $55 - then they changed that to $33 when I complained. Further discussion on my part pointing out that Sigma were apparently goint to fix the problem no charge in the US finally got them to drop the charges completely. I would think as the Sigma AND Pentax agents in Australia they should have worked out their position on this before anyone sent their flash unit in to be fixed. Not very professional if you ask me.
Mike M. (emem)
http://photobucket.com/albums/d179/emem48/

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MT Senior Member • Posts: 1,943
Thanks for this thread....

Thanks for this thread. when I posted various threads about my K10D focusing problems, some seem to doubt that my issues are real.

Anyways, after these new purchases in the past month: 360 flash, K10D, K100D, 12-24, TWO 50mm 1.4 and a limited on order, I'm going back to stay with my Canon solely because of the focusing issue. I did my test concurrently with a lowly Canon 350D and that old body was perfect.

This has been a VERY EXPENSIVE experience on my part, not to mention already having sold at least a Canon lens that I have to reacquire.

Sigh. I really trusted Pentax's technical expertise and the focus experience really blind sided me. I could not have guessed at that problem.

Note that I take lots of flash free shots indoor under existing artificial lighting. No choice. Part of my work.

Thanks for this post. Helped finalize my decision. S...I...G...H....

MTMT

ps: That part about Pentax's comment that analogue lens will not work up to standard on a DSLR is mind boggling.

Eric H Regular Member • Posts: 150
Re: Focusing problem with K10D

sunst8 wrote:

"There is nothing wrong with your camera or lens.

Please note that Pentax analogue lenses in use with your Pentax
digital
camera will not give the same focus performance as Pentax DA
lenses which have been specifically designed for digital use.

For best results with your analogue lenses please use lowest aperture
possible.

The above is true for all makes and brands.

You cannot expect perfect edge to edge focus on any digital camera
with any analogue lens.

We will arrange for return of your camera and lens after taking the
precaution to check at no charge."

When I spoke to Pentax just over a week ago they were still investigating the reports of consistent front-focus, but they claimed they couldn't reproduce similar results. Had someone said to me on the phone "well, we're aware of it but you have to realize our analogue lenses really aren't supposed to perform up to par on digital cameras" I would have asked how quickly they could send a refund check for all my Pentax gear. That's such a ridiculous position to take, especially since compatibility with all previous K-mount lenses is fairly well advertised for the K10D. I don't consider "reduced performance" and "compatibility" to be synonymous. I've already returned 2 50/1.4 lenses to B&H because they front-focused consistently on 3 different K10D bodies. I have 2 more on the way (from other retailers). If neither of them performs well, I may sell everything off and go back to Canon or hold out for Sony's next offering. The idea that consumers should buy a $1,000 camera with the expectation of reduced performance on the majority of available lenses is ridiculous and appalling.

sunst8 New Member • Posts: 3
Re: Sounds like typical CR Kennedy bulldust ...

That's what I thought and was a bit taken aback by such a response.

I have been a Pentax user since 1977 - my K2DMD with M50mmf1.2 lens is still a pleasure to use. I find manual focusing with its split-image fresnel screen is such a delight.

Perhaps if the K10D had such a screen I would enjoy manual focusing with the K10D more and not have to worry about using autofocus.

By the way, my response to the Pentax email was that it lacks a technical explanation as to why the camera will not focus accurately on a particular point when using spot focus.

If Pentax were to explain better I may be able to compensate for poor focusing with this lens. I am not after 'perfect edge to edge' focus, rather focus at the point aimed at using spot focus.

I guess this is the purpose of KSV posting. Any further assistance would be greatly appreciated as I am not about to give up my Pentax investment.

Voe
Voe Contributing Member • Posts: 528
Re: Focusing problem with K10D

Just for the record I searched through the Nikon forum for backfocus keyword and found that there are also people with problems in their D80. I guess it is a common issue in other major brands as well. So it is not only Pentax.

Anyway, I hope that it can be fixed by adjusting by a service technician. Or if you have the guts to DIY like this guy:
http://leongoodman.tripod.com/d70focuspart3.html

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Craig Jewell
Craig Jewell Senior Member • Posts: 1,182
Re: Focusing problem with K10D

I found similar behaviour with my kit lens, I got consistent front focus by quite a large margin up to about F6.3. On the focus chart, (at F3.5-4.5) the 20mm mark was in perfect focus, whereas the focus point was out of focus.

Under daylight or Triphosphor Flourescents (day light), the focus was generally spot on.

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steephill Veteran Member • Posts: 9,861
problem seems to be IR

Tungsten or incandescent light bulbs are very bright in near-IR and this seems to be confusing the AF sensor, particularly at low EV levels. The SAFOX AF system seems to be sensitive to near-IR and needs to be upgraded to cope. A hot mirror filter/coating will be required on either the auxilliary AF system mirror or more likely on the AF sensor assembly in order to cure this.

If it is an IR based miss-focusing problem there is no point in sending back lenses for replacement as the problem is not in the lenses, it is in the AF system in the body. And all bodies will have the same AF system so no point in changing bodies either. The only solution at present is to buy a hot mirror filter for the front of the lens or use manual focus when using very large apertures under tungsten lightining.

There will be other focusing problems of course as the lenses and bodies need to be calibrated properly in the first place and there will be sample variations. In these cases service or replacement will be the answer but user testing should be carried out first using daylight, not tungsten light.

There are probably enough users out there now with both a K10D and an FA50f1.4 to run a test to an agreed protocol e.g. f1.4 on a specified focus chart at 6 feet with a 60W clear tungsten bulb 3 feet above the target point as the only source of light. How about it?

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Laurens Senior Member • Posts: 1,391
Re: Focusing problem with K10D

When I was deciding on a DSLR purchar 2 years ago the Canon forum was full of people with AF problems whereas Pentax DSLRs didn't seem to suffer from this.

AFAIK there is no specification for the AF system accuracy on the Pentax SLRs, and assuming that they should all be spot on is unrealistic, for example the 77mm picture shown above would probably be acceptable, the 0mm line is still within the range of what people would regard as sharp. Other manufacturers may specify "within to DOF (with say a 0.02mm CoC)" or within 1/3 of the DOF.

The two lenses that give me inconsistent results in picture taking (leading me to do some tests) have been the DA40 and DA21 (ironically, DA lenses).

I believe that the Pentax AF system works (and is calibrated) as follows:

http://forums.dpreview.com/forums/message.asp?forum=1036&parent=21392379&thread=20912492"e=1

That also means that you can send, order and complain about as many lenses as you like but it's probably a body issue.

Laurens

Voe wrote:

Just for the record I searched through the Nikon forum for
backfocus keyword and found that there are also people with
problems in their D80. I guess it is a common issue in other major
brands as well. So it is not only Pentax.
Anyway, I hope that it can be fixed by adjusting by a service
technician. Or if you have the guts to DIY like this guy:
http://leongoodman.tripod.com/d70focuspart3.html

dvse New Member • Posts: 11
Re: Focusing problem with K10D

Laurens wrote:

When I was deciding on a DSLR purchar 2 years ago the Canon forum
was full of people with AF problems whereas Pentax DSLRs didn't
seem to suffer from this.

AFAIK there is no specification for the AF system accuracy on the
Pentax SLRs, and assuming that they should all be spot on is
unrealistic, for example the 77mm picture shown above would
probably be acceptable, the 0mm line is still within the range of
what people would regard as sharp. Other manufacturers may specify
"within to DOF (with say a 0.02mm CoC)" or within 1/3 of the DOF.

Good point. However, even if this is within the manufacturer's 'specification', systemic errors such as this are not very acceptable to the user given that the competition is free of them - at least Canon bodies/lenses can be recalibrated even if with only limited success where as the 'front focus under tungsten' is not curable through calibration for obvious reasons.

If we are able to gather convivncing evidence then hopefully Pentax will take action or at least the potential buyers will be aware.

jeffkrol Veteran Member • Posts: 6,225
If there is a problem w/ tungsten light

and it is due to IR contamination just try a Lecaish IR cut filter (hot mirror filter, watever) on the lens and see if improves AF. Have yet to see anyone try this. IF this is the case than a IR coating on the AF optical path would "cure " it. You would not be able to AF if you wanted to do IR photography anymore (as has been reported previously for Pentax bodies). This may just be an "engineering tradeoff" at this point. To AF w/ IR or not...
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