K-r Autofocus performance update..not good

Started Nov 26, 2011 | Discussions
Barry Fitzgerald Forum Pro • Posts: 29,888
K-r Autofocus performance update..not good

I'll just add before this post I was puzzled by the complaints about AF on this forum.

However today I shot some portraits in a low light environment lit with artificial light.

Out of the shots I took with phase detect AF I would estimate at least 60-70% missed AF, and by some margin in many cases despite AF confirm.

The camera displays no obvious problems in better light. Neither lens used shows any symptoms of AF issues in better light. Both the 90mm macro and 17-50mm showed serious AF problems in low light.

I can only conclude there is a serious issue with the low light AF performance of the K-r esp in some lighting conditions.

I noted the problem fairly quickly and switched to contrast AF live view. I worked around the issue, but I simply cannot afford to lose so many shots with an AF system that is as poor as this in low light. My Km5d is no champ for AF..in good light the K-r whips it and by a big margin. However I've never seen this number off missed AF shots from a camera before even the KM which could miss of course just like any camera, and it's not fast. But it's hit rate if far far higher than this, despite being a dated 2005 body.

As per another post I'm aware the central AF point is quite a bit larger than indicated and I attempted to compensate for this. But in most cases this didn't work. No degree of AF adjustment seems to work, it can hit AF once in a while! The odd time that is..but

I simply cannot afford to lose this number of shots for jobs like this. This was only a web job for a site so I'm not going to print, I might be able to focus magic a few if needed, but if I can't rely on the phase detect in low light it's an instant problem for me.

Question is this..

If it takes a K-5 to solve the problem I'll go that route and work around the issue in the for the time being and my Konica Minolta body is still in service and reliable, but I need honest feedback on this. If not then as I'm not heavily invested in Pentax and I have other options...

Very disappointing as the K-r is in many ways a great body lots of bang per buck. It's a huge let down to have this kind of issue. Maybe I should have stuck with the K-x because I never noticed this with that body.

As it is the K-r is not fit for purpose for low light shooting even my Fuji compact would kill it stone dead. Damn shame

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Brad99 Veteran Member • Posts: 3,145
Re: K-r Autofocus performance update..not good

I'm not a K-r owner but I've read a few things as it was a contender for a K100D upgrade..... have you tried taking your low light shots with Tungsten WB selected using the latest firmware as I believe Pentax incorporated a cludge fix for this problem, altering the AF in this mode to compensate somewhat for your problem.

OP Barry Fitzgerald Forum Pro • Posts: 29,888
Re: K-r Autofocus performance update..not good

Brad99 wrote:

I'm not a K-r owner but I've read a few things as it was a contender for a K100D upgrade..... have you tried taking your low light shots with Tungsten WB selected using the latest firmware as I believe Pentax incorporated a cludge fix for this problem, altering the AF in this mode to compensate somewhat for your problem.

I did that switched to Tungsten WB and it helped a bit, but did not cure the problem to a satisfactory level. I still got missed shots and quite a few in some cases by so much you'd wonder what you actually AF'ed on if you were not there.

Under fluorescent lighting and in somewhat better light the AF seemed a lot better yielding a decent level of hits way better than the first scenario

I noticed again the AF assist is simply not kicking in most of the time. This might be off-putting in some cases, but as you can turn it off it's not a problem. I'd rather hit shots with the AF assist then miss them with it not coming on.

At this stage it's not a problem to return it to the shop I'd be very doubtful anything can be achieved with a return to manufacturer. Frankly I'm amazed Pentax would allow a camera to be on sale with such a serious issue. Even the oldie *ist DL2 I tried seemed fairly reliable AF wise albeit some what slower.

I'd rather have slow and hit than fast and miss

Dale108
Dale108 Veteran Member • Posts: 8,699
Re: K-r Autofocus performance update..not good

Hi Barry:

I have both the Kr and K5 and the K5 is better under tungsten light than the Kr. You are correct in that there seems to be a bug in Kr focus system under these conditions. Luckily I don't use it much indoors.

Dale
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Terry k Regular Member • Posts: 102
Re: K-r Autofocus performance update..not good

This is a well known issue that the K-r has for focussing in tungsten light - and it doesn't need to be a very low light level - the camera badly front focusses in tungsten/halogen lighting (I curentlly own a K-r, which was a replacement for the first K-r which also had this problem, and was also sent back to Pentax repair to address this issue - and was not made any better). I also own a Pentax K100D and K20D. The K-r focus effect is much less problematic in fluorescent and LED lighting (and the K-r focuses fine in outdoor lighting). You can work around this issue by using LiveView focussing in tungsten lighting, but the focusing is much slower (and I don't like using Live View - I like having a dSLR, not a point and shoot camera feel). Shame on Pentax for never formally acknowledgng this serious problem with the K-r (much less doing anything to address the issue). Under tungsten lighting conditions, this really cripples what would be a great camera otherwise.

Pacerr Senior Member • Posts: 1,672
Re: K-r Autofocus performance update..not good

Your examples and commentary imply, to me, that your issue is with illuminating a selected point to focus on in certain conditions rather than tracking a moving target.

My answer to that situation is simple; momentarily augment the lighting on the point of focus with a pen light, room light or other device, lock focus and work with it as any other manual focus scene. Repeat a necessary. At least you're in control of the scenario rather than being distracted by a problem you apparently can't control with the conditions at hand. Sometimes you just have to accept the conditions you're dealt rather than the one you want or planned for.

Lighting for setup doesn't necessarily have to be that used for exposure and AF is actually a very recent tool in the evolution of picture making.

H2

OP Barry Fitzgerald Forum Pro • Posts: 29,888
Re: K-r Autofocus performance update..not good

Pacerr wrote:

Your examples and commentary imply, to me, that your issue is with illuminating a selected point to focus on in certain conditions rather than tracking a moving target.

I believe the problem is one of AF accuracy in low kelvin lighting temperatures.

During the shoot I attempted to find higher contrast areas but in this situation it simply didn't work

The wide angle shot was not that hard for the AF yet it failed miserably and worse didn't indicate a problem at all with AF confirm

My answer to that situation is simple; momentarily augment the lighting on the point of focus with a pen light, room light or other device, lock focus and work with it as any other manual focus scene. Repeat a necessary. At least you're in control of the scenario rather than being distracted by a problem you apparently can't control with the conditions at hand. Sometimes you just have to accept the conditions you're dealt rather than the one you want or planned for.

Using a pen light would distract the subject, but more to the point with the built in AF assist lamp not illuminating for almost all shots. I'd say that's a fairly easy fix via firmware.

Not that we're likely to see much action here but hey.

Lighting for setup doesn't necessarily have to be that used for exposure and AF is actually a very recent tool in the evolution of picture making.

Yet I cannot recall ever using a camera that performed so poorly in these conditions. Even my film bodies would rarely miss. I'm not trying to AF on ultra low contrast objects this really isn't that hard for the AF system.

Clearly there is a problem with Tungsten light and AF and as energy saving bulbs are also common in Europe that's a problem too. Fluorescent lighting isn't (least on the shots I have had, nor is daylight

A summary is:
AF accuracy is poor in low kelvin lighting (2500k-3000k odd)
Using Tungsten WB can help in some cases, but it does not "fix" the problem
Severe FF is shown almost always never BF
AF system confirms AF even when it has not hit the target

AF assist does not light when it's needed most rarely lights ever bar extreme darkness

Contrast AF does not appear to be an issue in this lighting. It's accuracy is much better, though it's slower (ok for this type of shot though) it does not always hit (the odd easy OOF shot now and then)
AF accuracy is good in other lighting conditions for both lenses used.

I'm not one to jump to conclusions but I shot a mixed lighting small concert and most of the phase detect AF shots were OOF using both lenses again. I had to use MF and Contrast AF because the phase detect was not even close on most shots.

Obviously this is a major issue so I've contacted Pentax UK to see what they have to say. I don't believe this is a "iffy body" because if that were the case it would show in other lighting conditions.

I'm obviously not accepting a body that has this issue. So my concerns now are if the K-5 is significantly better in these situations.

It is likely I will either return the body to the retailer or to Pentax as it does not meet my needs. But I'll see what they have to say and will update the forum as there are likely other K-r users who are having problems.

It would not be unreasonable to have expected Pentax to have been aware of the problem and to have modified the part/problem so that new production runs are not affected.

Carrying a torch around isn't a work around. For a new camera you shouldn't have to do workarounds on AF

888tg Forum Member • Posts: 69
Re: K-r Autofocus performance update..not good

Hi Barry, I just wanted to assure you that you are not alone with this problem.
Except low light focusing mess, this camera is a great tool.

I say mess because that what this situation is, a mess, it doesn't need to be a very low light either.

What puzzles me is that Pentax has technology to implement accurate low light focus as demonstrated on older bodies. Why wouldn't they use it on k-r is something that I don't get.
Best of luck, Teo.

OP Barry Fitzgerald Forum Pro • Posts: 29,888
Teo

888tg wrote:

Hi Barry, I just wanted to assure you that you are not alone with this problem.
Except low light focusing mess, this camera is a great tool.

I say mess because that what this situation is, a mess, it doesn't need to be a very low light either.

What puzzles me is that Pentax has technology to implement accurate low light focus as demonstrated on older bodies. Why wouldn't they use it on k-r is something that I don't get.
Best of luck, Teo.

Thanks

I think the situation is fairly clear. Folks might not know but back in 2006 KM had a defect with their KM5d. Buying late as I tend to do anyway, I did not avoid the problem and what you got was a situation where you'd power on your camera and your first shot was just a pure black frame.

It was know as "first black frame"

KM were aware of the situation and despite having sold off their camera division they did have a fix. A part in the shutter assembly was to blame. Over time it tended to get worse so not fixing it wasn't a sensible option for users.

Thanks to the efforts of community members on this they got KM to give people a free repair. You sent your camera in and they fixed it for free. I got mine done and it's worked fine ever since.

Pentax are going to have to acknowledge there is a problem with this model with the AF module. They are also going to have to provide a solution for it and offer a repair to users. There is no other alternative.

I'd like to give them the benefit of any doubt, but you can rest assured that I'm not one for giving up easily. I've emailed them with the problem and camera serial number, and I'll give them a few days to respond. If they don't I'll start chasing them up via phone if needed.

I would encourage Pentax K-r users to respond to this and contact Pentax and complain about the issue.

This one isn't going under the carpet because it's not fair on Pentax customers to have a flawed product which could and should be fixed. It's easy for me to offload my stuff and just buy something else, but I'd like to think the issue can get sorted out..if not the internet is a very good place for posting problems

888tg Forum Member • Posts: 69
Re: Teo

Hi again.

You can read my experiences with Pentax service in another thread about k-r focusing problem.
Go get them Barry!!!

Pacerr Senior Member • Posts: 1,672
Re: K-r Autofocus performance update..not good

Well, it's possible that the KR isn't the ideal tool for that particular job, or that YOUR particular KR isn't up to par, but my point was that one must work with what's at hand or quit the task -- and there ARE alternative means of achieving satisfactory focus. If all you have is a screw driver, it's pointless to attempt to drive nails but you might try glue or duct tape as an interim measure if you have a versatile tool box.

I do hope you find an exceptionally good deal on a tool that meets your expectations.

H2

OP Barry Fitzgerald Forum Pro • Posts: 29,888
Re: K-r Autofocus performance update..not good

Pacerr wrote:

Well, it's possible that the KR isn't the ideal tool for that particular job, or that YOUR particular KR isn't up to par, but my point was that one must work with what's at hand or quit the task -- and there ARE alternative means of achieving satisfactory focus. If all you have is a screw driver, it's pointless to attempt to drive nails but you might try glue or duct tape as an interim measure if you have a versatile tool box.

I'm sure you've read the post in detail where I explained that there is no question of mis calibration with the camera or lenses as they are perfectly fine in non tungsten light.

This is a unique problem, yes I have to respond and did by making other means of focus. Question is should I have to?

If you paid for a car and it didn't start in colder weather you'd likely be a tad annoyed. Same applies here.

My expectations are that a camera can AF in these conditions and not mis focus most of the time. You don't count how many are not in focus, because the number is far more than the in focus ones.

You can work around any issue, but this is simply not good enough and Pentax are going to have to sort the problem out, not for me but for all K-r users.

I do hope you find an exceptionally good deal on a tool that meets your expectations.

As the box didn't have a sticker on it saying "warning this camera blows for tungsten AF, do not buy if you want to take photos under these conditions" I think the many KR users out there, deserve far better

KR is a great camera, with awful AF in a specific light source

Ari Aikomus
Ari Aikomus Veteran Member • Posts: 9,443
Lack of secondary light color sensor ...

Hi Barry

Barry Fitzgerald wrote:

My expectations are that a camera can AF in these conditions and not mis focus most of the time. You don't count how many are not in focus, because the number is far more than the in focus ones.

You can work around any issue, but this is simply not good enough and Pentax are going to have to sort the problem out, not for me but for all K-r users.

Yep, It would be fair enough - but it's a fact that K-r lack secondary light color sensor (the 645D, K-5, and K-7 cameras all include a secondary light color sensor dedicated to determining the light source type, which is then taken into account when determining focus...K-r has Pentax's latest SAFOX IX system, but not that "+" version). I'm pretty sure that without secondary light color sensor AF isn't so good in tungsten light.

Pentax DSLR cameras' previous-generation SAFOX systems (like VIII version used in the K-x & K20D) works quite nicely in tungsten light, but this newer version include some other important AF improvements.

K-r's low light/tungsten AF issue is well know problem, and I guess that we (or Pentax/Ricoh) can't do much about it...

Except...Maybe you should use K-r's "AF fine adjustment" function always when you're shooting much in lowlight/tungsten light?

Nowadays I have K-5, and it works pretty good also under conditions like this, at least lowlight/tungsten situation is not huge problem for it.

cheers,
Ari

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OP Barry Fitzgerald Forum Pro • Posts: 29,888
Re: Lack of secondary light color sensor ...

Ari Aikomus wrote:

Yep, It would be fair enough - but it's a fact that K-r lack secondary light color sensor (the 645D, K-5, and K-7 cameras all include a secondary light color sensor dedicated to determining the light source type, which is then taken into account when determining focus...K-r has Pentax's latest SAFOX IX system, but not that "+" version). I'm pretty sure that without secondary light color sensor AF isn't so good in tungsten light.

There's not so good, and downright awful it's certainly the worst I've ever seen in a camera even going back to 35mm bodies I have.

Pentax DSLR cameras' previous-generation SAFOX systems (like VIII version used in the K-x & K20D) works quite nicely in tungsten light, but this newer version include some other important AF improvements.

I never noticed this with the K-x so I can assume it's a problem with the new Safox AF module.

K-r's low light/tungsten AF issue is well know problem, and I guess that we (or Pentax/Ricoh) can't do much about it...

They probably can do something about it, but of course it's going to cost money.

Except...Maybe you should use K-r's "AF fine adjustment" function always when you're shooting much in lowlight/tungsten light?

If you look at the samples I posted the degree of FF is severe, so much so it's well beyond any AF adjustment range in many cases.

I think K-r users are going to have to get a bit tough with Pentax on this. It might cost them to fix it but ultimately they should have adequately tested the new AF module before they released it.

Making an informed buying choice had I known it was this severe no I would not have bought a K-r body.

The responsibility is with Pentax to address the problem, if they can't they'll have to source a new AF module and offer it as a free repair.

MightyMike Forum Pro • Posts: 40,698
Re: K-r Autofocus performance update..not good

I'm willing to bet that Pentax and other brands recently made alterations to how their AF sensors work or detect light, it probably was seen as an improvement in many shooting situations and a potential problem in some situations, clearly this wasn't a problem in previous models implementations.

I would hope that the next generation of cameras have this issue fixed but i won't hold my breath, so far my K-5 doesn't exhibit such an issue that i've noticed.
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Gary Martin
Gary Martin Veteran Member • Posts: 4,771
Re: K-r Autofocus performance update..not good

This has been a well-known issue with the K-r, I'm surprised you didn't find out about this problem before you made your purchase. My K-r will front-focus in low light if it is tungsten; in fluorescent or daylight I don't have the problem. Fortunately, I seldom shoot in tungsten lighting, and if I need to I will use my K200D instead, especially with a fast lens like the FA50. Unfortunately, Pentax has been silent on the issue. I hope that Ricoh can improve Pentax QC, which has not been great the last few years.

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Anirut J
Anirut J Regular Member • Posts: 257
Here's a "guess work" work around

I knew the problem existed and yet bought the K-r for it's other cpabilities.

If I have enough time to work around the tungsten FF problem, I deliberately focus "behind" the point/area I want to be in focus.

e.g. A person's face looking straight in tungsten light.

I would bring K-r's good high ISO capability to the advantage and would use f-8 or f-11 for good DOF and deliberately focus at an ear so that the K-r will FF at around the cheek or nose.

From my experiments, the tungsten FF distance varies proportionately with the distance you're away from your subject, and this varies your with your lens too. From the same distance, a wideangle lens will have more FF than a tele lens. This will take some experiments to know a good approximation of the FF distance to use the "focus behind" work around.

Of course, this is a pain.

Or I would just use manual focus with a narrower f-stop. Sometimes it's faster, especially that the camera may have to hunt in low light.

My 2 cents ...
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OP Barry Fitzgerald Forum Pro • Posts: 29,888
Not a "lens issue" folks

Tamron 90mm f2.8

This is contrast AF for the 17-50mm

Contrast AF again

In some cases the degree of focus miss is less with tungsten preset but it's still not great at times.

Contrast AF is not a magic bullet it can be slightly off at times and it can miss when it does miss it usually does so fairly obviously.

Neither lens had any notable or serious issues when I used them under fluorescent lighting

awaldram
awaldram Forum Pro • Posts: 13,271
Re: K-r Autofocus performance update..not good

Seems to me the newer sensors used in AF are partially blind to the red spectrum, This probably improves contrast detect.

But is detrimental to phase detect tungsten light shooting. Manufacturers probably worked on the fact that newer environmental laws have practically banned the use of Tungsten light so it wouldn't be an issue.

Unfortunately some countries aren't banging the same 'environmental' drum as the rest of the world.

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OP Barry Fitzgerald Forum Pro • Posts: 29,888
Re: K-r Autofocus performance update..not good

awaldram wrote:

Seems to me the newer sensors used in AF are partially blind to the red spectrum, This probably improves contrast detect.

But is detrimental to phase detect tungsten light shooting. Manufacturers probably worked on the fact that newer environmental laws have practically banned the use of Tungsten light so it wouldn't be an issue.

Unfortunately some countries aren't banging the same 'environmental' drum as the rest of the world.

This isn't exactly correct it's not about eco issues at all. Energy saving bulbs (very common in Europe and by far the most likely indoor light source for most homes) are the main use..NOT the oldie type light bulbs.

The issue is present with these energy "eco" bulbs in the same way it is for traditional tungsten bulbs. So we can't blame the type of bulb because it is eco friendly (bar the mercury used in manufacturing) they are very energy efficient and many are around the 2500k-2900k spectrum

It's obviously a fault with the AF sensors as my many other cameras I have used and owned do not display any issues at all in this kind of lighting. Lower light levels obviously it's more of a challenge, but then some of the shots were really not that hard to nail and not even that low light.

So it's not purely about low light, mostly about the colour temp of the light.

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