Originally posted by AndyNick I think I have a different situation to most, having developed the stain after some heavy use.
The first attachment below was taken on December 6th and I found a very slight shadow that resembled the reported stain, but wasn't anything to worry about in my regular use. You may be able to make it out about a third the way down, two-thirds across. Thinking it was dust my blower and the Dust Removal couldn't shake off, I ordered the O-ICK1 cleaning kit. Before it arrived I had a party to photograph on the weekend and shot off over 500 pictures in a little under three hours. Checking the sensor again on Monday, found the string of dots close to the shadow, obvious in the second attachment below. I've used the blower, run the Dust Removal again, and stuck the O-ICK1 in there to clean as best I could - with no change to the original shadow and the new string of dots.
Both crops are 100%, shot at f22. Camera was ordered online in Japan, delivered October 29th, Serial number 3829###.
AndyNick has kindly asked my opinion on his case. I'll try my best
First and most interestingly, this is the first significant report I see that a string of pearls may develop in the field. If it can be confirmed, it puts the cover glass imperfection explaination at doubt. So, extra care must be applied in this case.
ATM, I'm not sure what I see. It looks like a string of pearls. But the individual stains seem to be a bit soft (no clear halo) for the typical stain we know, at f/22.
The slight shadow is nice as it does allow to compare the scale and position of the two crops. In itself of course, it is nothing.
I think we need some more tests.
Andy, can you shoot additional tests at f/11 16 22 32 and ideally a f/32 with a macro at closest distance. Maybe even a pinhole shot? I'd like to be sure w're not seeing a strange alien visiting the top of the AA filter
If it can be confirmed, Pentax should be made aware of this particular case.
There is theoretical chance of course, that the cover glass imperfection develops after mechanical tension due to heat. If this is the case, one should do the string of pearls test after a first video session until temperature warning. When I first searched and found MY stains, I already happened to use video this long. However, further tests did NOT agravate the issue anymore. So, I have one more question:
Andy, when you did the first photo w/o the new string, did you use video or LV for more than a few trials before?