Some K-5s shipped with stains on the sensor/AA filter?

Started Dec 4, 2010 | Discussions thread
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Pete Fang Senior Member • Posts: 1,900
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:

f/22:

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.

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:

http://forum.xitek.com/showthread.php?threadid=812805

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.

Best,

Peter

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Peter Fang - Pentax user for more than 25 years: K-5 / MZ-S / Z-1 / SFX / LX
My Online Gallery: http://petefang.smugmug.com/

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