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12-03-2010, 10:01 PM   #1
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Some K-5s shipped with stains on the sensor/AA filter?

Hi Everyone,

It was only during the past week that I noticed this: A few users who purchased the first batch of K-5s in mainland China, Hong Kong and Taiwan have posted to Chinese language forums about signs of stains they found on the sensor or the AA filter of their K-5s. The situation quick accelerate to a state that more than twenty people now have claimed to have observed this issue and a majority of them have posted sample images to forums. Some of these users have already taken their cameras back to the distributors. It looks like Pentax is aware of the issue and will replace the affected bodies free of charge after some simple tests.

I had been extremely busy for the past week but I was curious after reading all those local discussions. So I did my own test and I did find out that my K-5 also has stains near the center of the image sensor or the AA filter although I cannot tell exactly where the stains are. I used an LED flashlight and looked at the sensor directly with the mirror up and I could see a small trait of dirt (around 1.5mm long) near the center. It looks a little bit like the leftover of adhesive material when you peel off a sticker but didn't do it right. This could be introduced during the assembling process at the factory.

My test process is as follows: K-5 with the FA31 Limited, I started testing from f/8 and went all the way through f/22. I pointed the camera at a blank white page of my 27" iMac LCD and focused to infinity so the LCD just served as a uniformed white light source. I can start seeing the stains (just barely) at f/11 and it becomes quite visible at 100% view at f/22. Here's how it looks at f/11 and f/22 (100% crops):

f/11:

http://petefang.smugmug.com/Images-from-reviews-and-tests/Pentax-K-5-Samples...55_4zzp8-O.jpg

f/22:

http://petefang.smugmug.com/Images-from-reviews-and-tests/Pentax-K-5-Samples...75_Q8TT3-O.jpg

To put things in perspective, here's a 1920x1280 downsized version of the whole f/22 image, if you look carefully you can find the stains near the center, slightly to the lower right direction:

http://petefang.smugmug.com/Images-from-reviews-and-tests/Pentax-K-5-Samples...94_wkjwa-O.jpg

Let me be clear that those stains are not the same as dusts on the outer side of the AA filter. Dusts appear as bigger, rounder and more out-of-focus in the images and can be easily cleaned by using the dust removal function or an air blower. Some Chinese users reported they had their K-5s tested at a distributor in Shanghai and were told the stains were not on the outer side but in between the sensor and the AA filter, therefore hard to be cleaned easily.

So to sum up, I haven't noticed this in real world images in the few weeks after I purchased the K-5, partly because I almost never use apertures smaller than f/11. I probably won't notice anything in the future either in my real world use of the camera. Based on the recommendation from my distributor, I still sent my K-5 back to them and see how it turns out. I encourage other K-5 owners to conduct a similar test and see if you can find similar signs of stain. Will this affect your everyday photography? Probably not. Does this make the K-5 a problematic camera? No. The K-5 is still the most balanced picture-taking tool that Pentax has produced in the digital age. I think the likely outcome of this is Pentax exchange affected bodies for new units and as soon as they find what was causing this in the manufacturing process I am sure we won't see more cases of this issue.

As a reference, this is the Chinese discussion thread that chronicles this issue very thoroughly:

排除争吵 总结讨论 PENTAX宾得K-5污点问题 请各方勇敢面对 - 无忌论坛

Let us know if you have similar issues but don't let this small issue stop you from enjoying taking pictures with this wonderful camera. Nobody shoots blank walls everyday. emoticon - smile

Best,

Peter


Last edited by Peter Fang; 12-03-2010 at 10:06 PM.
12-03-2010, 10:11 PM   #2
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Having answered this on the DPReview thread as well, I wanted to do the same here. However, I also want to say that I am somewhat surprised to see it being brought-up this way considering that it has been a prodigy of RiceHigh's blog for sometime now.

In any case, the issue seems fairly isolated to date, and though I'm not discounting the value of verifying this at time of purchase(I know I would).
It does look as though this was limited to only a few of the earlier units.

Which leads me to ask if anyone recorded the serial numbers for any of the affected units?
12-03-2010, 10:37 PM   #3
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QuoteOriginally posted by JohnBee Quote
Having answered this on the DPReview thread as well, I wanted to do the same here. However, I also want to say that I am somewhat surprised to see it being brought-up this way considering that it has been a prodigy of RiceHigh's blog for sometime now.
It's funny that you mentioned RH's blog. I actually said in the Chinese discussion thread yesterday that since the issue were reported by a few Hong Kong users already, I wondered why RH hasn't picked it up yet. And the next morning, I saw him linking the same thread in his new blog article!

Peter
12-03-2010, 10:42 PM   #4
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Yea he is quick to pick-up on things like that
However, if memory serves me correctly, I think RH reported this earlier too.
I don't think I received much attention as it the numbers may of been much more isolated than they are now. But I'm fairly certain it was posted before(I'll have a look around).

Other than that, I've been reading far more people reporting this now than they were earlier. Which is quite sad to say the least. And I'm wondering if they are all subject to the exact same situation?

ie. Who has tried a wet clean prior to calling it and are they all the same sort of conditions?


JohnBee added later...

Okay I dbl checked RH's blog and found a reference on: Saturday, Monday, November 29, 2010 entitled:
Scratched "Sensor" Cases of the K-5 Units - Quality Issue of the AA Filters Manufactured by Pentax?
So it looks like its been covered a bit earlier as suspected, but most likely didn't get enough attention to warrant anything other than the status of isolate defects.

Well for what its worth, I am very sorry to hear about those of you who got caught-with this. I know I would be most disappointed if I found-out my own unit had a defect.


Last edited by JohnBee; 12-03-2010 at 11:25 PM.
12-03-2010, 10:54 PM   #5
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QuoteOriginally posted by JohnBee Quote
Other than that, I've been reading far more people reporting this now than they were earlier. Which is quite sad to say the least. And I'm wondering if they are all subject to the exact same situation?

ie. Who has tried a wet clean prior to calling it and are they all the same sort of conditions?
I tried using Pentax's O-ICK1 sensor cleaning kit but it did not improve the situation at all. In fact I can't even be sure if the stains were on the outer side of the AA filter. I did not dare to use other methods to try cleaning it, fearing that I may cause my own scratches.

A few users who returned their units to the Shanghai distributor were told by the engineers there that it was between the CMOS and the AA filter. The engineers tried to remove the AA filter but said they couldn't due to a change of design since the K-5. It is possible that the AA filter is assembled differently compared with the Samsung sensor used by the K20D/K-7.

I will wait for updates from my distributor. I know them rather well and I believe they will let me know whatever verdict that comes out of Pentax.

Peter
12-04-2010, 12:16 AM   #6
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Ok, you made me look. I am #5 on our Serial Number list so I got an early one on Oct. 15 but no stains or marks I can see by shooting the ceiling at f/22. Its not all the early ones.
12-04-2010, 12:44 AM   #7
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sorry to bring this out of topic but what is an AA filter?
12-04-2010, 03:53 AM   #8
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Damn, my K-5 seem to be affected I noticed this on macro shots, now double checked again. It's a line of strange dots in the middle and impossible to remove, neither by built-in ultrasonic sensor cleaning, nor by blower (which successfully removed a few real dust spots). I don't really want to wait several weeks for repair or exchange... it doesn't affect normal shots, but ruins macro shots where I can't clone them out without destroying fine details / texture of the subject.

12-04-2010, 04:08 AM   #9
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QuoteOriginally posted by Pablom Quote
sorry to bring this out of topic but what is an AA filter?
An AA filter stands for an Anti-Aliasing filter and is something that sits in front of the sensor in most dSLRs. When you lift up the mirror to clean your camera sensor, you're actually cleaning the piece of glass (AA filter) that sits in front of the sensor and don't actually touch the sensor at all.
The filter is in place to reduce aliasing, and moire effects.
12-04-2010, 04:29 AM   #10
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Looks like oil or something, my k20d had a huge spot I saw first time I used it. I got it off with vigorous use of the rocket blower. An oil spot would need a wet clean. Though you don't want a dirty sensor on a new camera, sensor cleaning is a fact of life.
12-04-2010, 07:58 AM   #11
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So, I went ahead and took some test shots of a white monitor screen, and sure enough, there it is. I did the sensor cleaning routine and used the blower with no effect. I will pixel peep images for a while before deciding whether or not to have Pentax fix it.
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12-04-2010, 09:56 AM   #12
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same problem here
12-04-2010, 10:40 AM   #13
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How do you guys know that a wet sensor clean would not solve the issue?
12-04-2010, 10:54 AM   #14
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Thanks guys for identifying the problem, I hope Pentax will address the issues quickly and decisively. Hopefully by the time I am ready to move from k-7 to k-5 next year (saving up for it now), the problems will be resolved and forgotten.
12-04-2010, 10:58 AM   #15
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QuoteOriginally posted by imtheguy Quote
Ok, you made me look. I am #5 on our Serial Number list so I got an early one on Oct. 15 but no stains or marks I can see by shooting the ceiling at f/22. Its not all the early ones.
Just so you make sure you don't end up with the issue. From my reading, a few people who have noticed the issue for a longer period have seen it become worse with time. The gist of what I have read is it could be somehow related to an issue with maybe the sealant used for the AA filter losing it's integrity under higher temp condition. More than a couple people indicated they did not notice the problem until using video for an extended period.

So maybe just to cya, if you haven't tried video for a long enough period to heat up the sensor assembly enough give it a try. You know, just to be sure. But don't try heating up the sensor to see if the issue develops until you know you can be w/o the body for however long it is taking to repair/replace the sensor assembly or whole body.
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