[Rondec]

Got my 3rd K5 this week (first one had sensor stains, second one front focus issues, 3rd is stain free but still has FF).

It appears to be a bit better in low light, but still has significant front focus at EV 2-3.

Here is a test sequence, 3rd K5 on top, 2nd K5 in the middle, K20 last, EV 11 on the left to EV 2 on the right:



FA 50 @ f2.8, ISO 100, AF and 2 sec MLU/Shutter release tripped by IR remote. No sunshine today, so I used my SSC P7 led flashlight to illuminate the target and placed ND filters over the light to reduce it 8 and 10 stops.

Note that "white" leds are not really white as they have very little response in the red spectrum. In this case, the camera saw more and more green as the led light was reduced, which is another nail in the IR color shift myth. The SSC P7 LED white led is nominally 6400K and I measured 6150 at full brightness, 5400 at the lowest light level, so this test does not isolate color vesus light level, not that I believe this makes any difference, as I do not.

All AF adjusts were reset, so you can see some differences in starting focus point.

The good news is that while the 3rd K5 (top) still has a bad shift at the lowest light level, it holds up much better to just above the steep drop-off at EV 2-3.

It may be that I can dial AF adjustments that are biased towards the back a bit in bright light and still get good focus at least to EV 2-3 or so.

The K20D works just as I expected. It tends to FF as well, but is much less certain in getting a lock in low light, hunting a bit more and actually locking into a somewhat worse FF position in the middle image than in the lowest light. It is much better at the lowest light level than either K5.

I had the FA 50 dialed to a bit of BF in daylight on the K20D, which keeps it within the DOF as the ight is reduced.

So, I have tested my cameras with reduced daylight, reduced tungsten light, reduced led light that shifted green and also with different colors, and the only consistent result is that the camera shifts to FF as the light is reduced and has a steep FF shift somewhere around EV 2-4.

There may well be K5s that do not FF this badly at EV 3 and below, but I am on my 3rd body and they all had a very similar problem in low light. I would really like to see a test from a K5 at EV 2-3 F2.8 or so that does not FF like this. At least then I would have some hope that the K5 can focus somewhere near the advertised specification of -1 EV.

No more testing for me, however, as I am convinced that there is a consistent AF problem with the K5 and I have little faith that Pentax will do any more about this than they have with SDM failures, or KR FF in low light issues, or K10D AF in low light issues.

I guess that I need to decide if it s time to seriously consider moving to another brand, as much as I do not want to do so for many reasons.

Ray

EDIT: 2nd K5 has latest firmware (middle images) 3rd K5 does not (top images).

I would wait a little while. All indications are that Pentax knows about this problem and is working to fix it. Unfortunately, it isn't an easy fix, like adding functionality to a specific button, or fixing some minor software glitch. In another week or two, they will announce a firmware update and everything will be "better," although I expect them to be a little cryptic in their description of the fix.

[Douglas_of_Sweden]

As the administrator, for good reasons, has closed the former thread re this issue I would like to suggest that the issue still has a right for following up in this forum so please post your RELEVANT developments/ thoughts/ ideas/news in this thread so we can keep an eye on the issue as long as it is not solved.
Agree ?

In the spirit of Glasnost: the AF issue and sensor stain threads were closed because the discussion got off-topic/unproductive and - worse - unfriendly. As far as I know starting new threads to continue to discuss the actual issues is absolutely fine, if you feel that it is still needed.

Non of us moderators thought the topic wrong. But keep it polite and on the subject this time. Threads that get out of hand, where several reports, warnings and infractions have no effect, leave us no choice. I can recommend reading the forum rules again if you haven't done it for some time.

[simico]

The other topic was closed just before I wanted to share my experience, so I write it here.

My original K-5 had severe front focus under my living room's tungsten light (EV 4.4). This was pretty obvious on all of the images. That camera had been replaced due to stain issue and I got the replacement K-5 just one day before Christmas. To my surprise and satisfaction, this camera worked absolutely fine during Christmas evening in low tungsten light.

On Friday evening I did a quick test: put my cam on tripod, 2sec delay, set up the user manual book as target first 2 meters away then second time 60cm way, a ruler was put nearby the book to check DoF and focus point. Took shots under tungsten light first using our 32W "energy saver" chandelier (? it this the right word?) which means EV 4.4, then using only a small 20W traditional tungsten desk lamp bouncing its light off the wall which means EV 2.6, each time taking one shot with AWB and another with Tungsten WB. I used Sigma 30 f/1.4 and DA* 16-50 f/2.8 (at 30mm), both wide open. Focus ring was turned to infinity after each shot to force re-focusing. I also took a control shot in LiveView with contrast detect AF. So at the end I ended up with 18 shots in total.
Results: 1 shot came out back focused, 1 came out slightly front focused. Rest came out spot on, with 2 shot slightly shifted toward front but target still being in focus. There was absolutely no difference between shots taken with AWB and Tungsten WB, i.e. setting Tungsten WB made no difference at all.

So it seems my replacement K-5 does not exhibit the severe front focusing under low tungsten light as the previous camera, at least I haven't seen any evidence of that either in my mini test or in normal shots taken so far. I've taken a few hundreds shots since getting it and the number of misfocused images are very low, it's within my user error threshold

Does this mean the severe FF issue in low tungsten light might be caused by hardware issue in some units? I don't know. I'll certainly keep an eye on my low light shots and will try to do some night shots below EV 2.6 when I get some time (and can overcome my laziness to out at night). I hope that my current camera will keep focusing fine in our living room and other environments with low and tungsten light.

[Rupert]

I realize this is a problem for many shooters and their style of shooting, while I doubt it would matter much for me in most situations where I shoot. I am wondering about the reports of the focus light failing to operate until it is very dark in the scene.......the light would most likely be all I would need. Is there any way to force this to come on? With the light on, has it shown to eliminate the FF problem?
Best Regards!

[aliasant]

I did some testing today and found severe FF with my Pentax-A 50mm f1.7 but not any at all with my Tokina A 90mm f2.5.

I used a stand aimed at a fixed ruler at 45 degrees and a distance of about 60cm.
f2.0 on the Pentax 50 and 2.5 on the Tokina.

I first took pictures with the two lenses during daylight. No problems found.

Went back when daylight was gone and did the same under Tungsten and AW and only the Pentax 50 was off but it was off by 2 inches when I tested using the viewfinder and perhaps half an inch using the LV.

Why only the Pentax and not the Tokina under the same relatively exact circumstances?

[Ray Pulley]

I realize this is a problem for many shooters and their style of shooting, while I doubt it would matter much for me in most situations where I shoot. I am wondering about the reports of the focus light failing to operate until it is very dark in the scene.......the light would most likely be all I would need. Is there any way to force this to come on? With the light on, has it shown to eliminate the FF problem?
Best Regards!

Hi Rupert,

I am quite amazed at how dark it can be before the AF assist comes on in PD AF (non-live view) focus mode. I have never seen it come on using the center point only in levels as dark as EV 2 and below. However, I have a target with good contrast as it is a black and white test target.

I have been able to make it come on in this light level by switching to another point, but it is almost as if the camera does not care about the metered light level at all, it seems to only come on if it thinks it cannot find enough contrast to focus on.

How it decides this is not clear to me.

The light comes on much earlier in live view focus mode.

I am also amazed at how low the light level can be and still have the PDAF system lock (albeit at a significant FF) where the K20d hunted or gave up. This is one of the reasons for a tiny bit of hope for a firmware fix, along with the fact that the FF behavior has a consistent drop at a pretty consistent light level, which might mean there is a correction being applied that has gone awry.


Ray

[KungPOW]

I did some testing today and found severe FF with my Pentax-A 50mm f1.7 but not any at all with my Tokina A 90mm f2.5.

I used a stand aimed at a fixed ruler at 45 degrees and a distance of about 60cm.
f2.0 on the Pentax 50 and 2.5 on the Tokina.

I first took pictures with the two lenses during daylight. No problems found.

Went back when daylight was gone and did the same under Tungsten and AW and only the Pentax 50 was off but it was off by 2 inches when I tested using the viewfinder and perhaps half an inch using the LV.

Why only the Pentax and not the Tokina under the same relatively exact circumstances?

Because some lenses let through more IR light then others. Zoom lenses scatter more IR light then do primes. So, the prime lens will have more IR light to focus with then does the zoom. The result is that the prime will be more out of focus then the zoom. But If you are doing IR photography, you will get a sharper image from teh prime.

Here is a good read:

Ernitec - IR corrected lenses

[Tommot1965]

The other topic was closed just before I wanted to share my experience, so I write it here.

My original K-5 had severe front focus under my living room's tungsten light (EV 4.4). This was pretty obvious on all of the images. That camera had been replaced due to stain issue and I got the replacement K-5 just one day before Christmas. To my surprise and satisfaction, this camera worked absolutely fine during Christmas evening in low tungsten light.

On Friday evening I did a quick test: put my cam on tripod, 2sec delay, set up the user manual book as target first 2 meters away then second time 60cm way, a ruler was put nearby the book to check DoF and focus point. Took shots under tungsten light first using our 32W "energy saver" chandelier (? it this the right word?) which means EV 4.4, then using only a small 20W traditional tungsten desk lamp bouncing its light off the wall which means EV 2.6, each time taking one shot with AWB and another with Tungsten WB. I used Sigma 30 f/1.4 and DA* 16-50 f/2.8 (at 30mm), both wide open. Focus ring was turned to infinity after each shot to force re-focusing. I also took a control shot in LiveView with contrast detect AF. So at the end I ended up with 18 shots in total.
Results: 1 shot came out back focused, 1 came out slightly front focused. Rest came out spot on, with 2 shot slightly shifted toward front but target still being in focus. There was absolutely no difference between shots taken with AWB and Tungsten WB, i.e. setting Tungsten WB made no difference at all.

So it seems my replacement K-5 does not exhibit the severe front focusing under low tungsten light as the previous camera, at least I haven't seen any evidence of that either in my mini test or in normal shots taken so far. I've taken a few hundreds shots since getting it and the number of misfocused images are very low, it's within my user error threshold

Does this mean the severe FF issue in low tungsten light might be caused by hardware issue in some units? I don't know. I'll certainly keep an eye on my low light shots and will try to do some night shots below EV 2.6 when I get some time (and can overcome my laziness to out at night). I hope that my current camera will keep focusing fine in our living room and other environments with low and tungsten light.

Interesting..thanks for doing a thorough test....could I please ask your serial number and production date of the body...you can find that using Photome..

if my next FW update doesn't fix mine..Ill refer to yours when dealing with Pentax

[tibor]

Personally, I believe that the AF problem is caused by HARDWARE VARIABILITY + actual level of QC (it should normally filter out the damaged cameras).

I PERSONALLY handled my friend's camera and it had MUCH BETTER AF with an identical FA 31 and FA 43 in comparison with AF performance of my K-5.

Differences:

1: Low light capability: an ultra precise AF vs. strong FF

2: AF's "torque": This was for me the most interesting observation. The correct K-5 had much more physical power during AF - I wouldn't t say a faster one, but definitely a more POWERFUL one, I was able to clearly feel the difference in the slight jerk during lens barrel rotation and a kind of decisiveness during each refocusing phase. I do not know how to describe it better... the AF in the correct camera is significantly more ALIVE, my K-5 is a "half-dead fish" in comparison to it.

So, I am quite convinced that there ARE perfectly focusing K-5 bodies on the market and I tend to believe that their percentage is increasing due to improved QC.

Hope someone with technical background can bring a bit more light to this issue.


Cheers,

Tibor

[Inspector 17]

That the correct one felt like more power/"torque" may suggest that weaker batteries may be a contributor to the problem.

Are you aware of any difference in battery charge state?

Personally, I believe that the AF problem is caused by HARDWARE VARIABILITY + actual level of QC (it should normally filter out the damaged cameras).

I PERSONALLY handled my friend's camera and it had MUCH BETTER AF with an identical FA 31 and FA 43 in comparison with AF performance of my K-5.

Differences:

1: Low light capability: an ultra precise AF vs. strong FF

2: AF's "torque": This was for me the most interesting observation. The correct K-5 had much more physical power during AF - I wouldn't t say a faster one, but definitely a more POWERFUL one, I was able to clearly feel the difference in the slight jerk during lens barrel rotation and a kind of decisiveness during each refocusing phase. I do not know how to describe it better... the AF in the correct camera is significantly more ALIVE, my K-5 is a "half-dead fish" in comparison to it.

So, I am quite convinced that there ARE perfectly focusing K-5 bodies on the market and I tend to believe that their percentage is increasing due to improved QC.

Hope someone with technical background can bring a bit more light to this issue.


Cheers,

Tibor

[Bobe416]

I did some testing today and found severe FF with my Pentax-A 50mm f1.7 but not any at all with my Tokina A 90mm f2.5.

I used a stand aimed at a fixed ruler at 45 degrees and a distance of about 60cm.
f2.0 on the Pentax 50 and 2.5 on the Tokina.

I first took pictures with the two lenses during daylight. No problems found.

Went back when daylight was gone and did the same under Tungsten and AW and only the Pentax 50 was off but it was off by 2 inches when I tested using the viewfinder and perhaps half an inch using the LV.

Why only the Pentax and not the Tokina under the same relatively exact circumstances?

I am a little confused here - If I understand it correctly the pentax A50mm f1.7 is a manual focus lens, yet the thread is talking about auto focus. Hmmm?

[ovim]

I am a little confused here - If I understand it correctly the pentax A50mm f1.7 is a manual focus lens, yet the thread is talking about auto focus. Hmmm?

Maybe he tested when the focus confirmation would light up?

[aliasant]

Maybe he tested when the focus confirmation would light up?

Yes of course. Thanks : )

This is a problem for manual lenses aswell.

I was wrong about one thing though.
This is a problem during any light situation and not specific to Tungsten.

When i did the test with manual lenses i had focus confirmation in the viewfinder & my katzeye looked perfectly in focus yet the shot is front focused by 2 inches.

In a way its even worse for manual lenses since they cant be
individually corrected.

I thought i should share that as another piece of the puzzle.

I want to add to this that I also tested other manual lenses and it seems to get worse with wider lenses but not consistent.
I tested some different 55mm 1.8s and they were all slightly different.
One Mamiyar SX 55mm was about 1" FF.
My Topcor 58 1.8 was perhaps 1/2" so åretty close.

I also tested my Tamron SP 35-80 at different ranges and it was perfect at 80 and almost perfect at 60 but as I got closer to 50 it got worse and it really decayed when I went under 45mm.
My Tamron 28mm 2.8 Adaptall-2 is of the charts.
At least 4 inches FF.

I did also test the same lens in the same test setup on my Kx and there are no FF problems with the Kx.
My Pentax-A 50mm f1.7 is dead on using the Kx but 2 inches front focused using the K-5.
I havnt tried the other lenses on the Kx but Im guessing there arnt any problems.


Isnt this relevant?

If you guys want some kind of image proof I guess I can do that but I dont want to spam this thread with big images unless asked to.
Maybe this is only my K5 that is behaving weird so if someone else can test this too that would be very helpfull.

Im not to worried myself since I already have the paperwork done so I can send my K5 back anytime and get a new one within days but I want to wait until they have a new stock with working cameras.

[simico]

Interesting..thanks for doing a thorough test....could I please ask your serial number and production date of the body...you can find that using Photome..

S/N 3885917, date is 2010 November.

[Tommot1965]

S/N 3885917, date is 2010 November.

cheers

same build date as mine..although mines a 39** serial