[blende8]

Quantum strings and vacuum bubbles ...

[falconeye]

I have 1 stain on the upper left side, such a shame, I am afraid of getting a replacement and having the same issue....

Single stains are rather normal. A replacement can well be worse, any brand. My K-7 has one too. Look at f/32 though.

Mine seems to be slightly different to everyone elses.

With Arago spots. f/32 close focus?
Looks like two parallel strings (or a cluster) of stains. This is what we're looking for

[Wheatfield]

Regardless, it was Pentax's responsibility to catch the QC issue before sending it out.

Actually, it is Pentax's responsibility to do warranty repairs on problem equipment. The reality of the brave new world of cameras being as cheap as possible means the end user is the quality control department.
It's unfortunate, but with people always complaining about the cost of new equipment, and willing to switch systems for a few dollar saving, we can't expect a lot of QC that is going to raise the price of the equipment significantly.

[falconeye]

I just saw this (posted yesterday):

One of the ching whom had this problem but solved,

Called me and we have a little chat,

According to jebsen,

The spot was actually apperaed on the back of the cmos,

Not at the front ......

[source: Google Übersetzer ]

If you look at my original estimate (the OP), the stains sit within the cover glass. Because the exact position was closer to the upper surface, I deduced upper glass cover surface in the gap between chip and AA filter.

But maybe, we shouldn't already exclude the other possibility:

That the stains sit on the inner surface of the chip's glass cover. It would then be a defect Sony is responsible for.

[ogl]

Service Notice: EOS-1D Mark III/EOS-1Ds Mark III: Oil Spots on LPF Surface

[Wheatfield]

Service Notice: EOS-1D Mark III/EOS-1Ds Mark III: Oil Spots on LPF Surface

Wow, I could have spent 5 grand more than what my K5 cost me and had spots?
Once again, Pentax shows itself as a value leader.

[Douglas_of_Sweden]

Interresting reading.

...I start from the most simple hypothesis I can make: that the stains are caused by opaque disk-shaped obstructions somewhere in the light path.

...The fact that this bright spot forms exactly as predicted by our opaque disk-shape obstruction hypothesis is a strong supportive argument. There is no evidence that the stain is from a liquid or oil particle.

...Everything combined, this means that the upper left stain is created by a round opaque particle of a bit less than 1/20 mm diameter and sitting between maybe 0.68 mm and 0.78 mm above the sensor. So, this determines the vertical particle position with about 1/20 mm precision which is about its diameter. Other stains seem to come from somewhat smaller particles.


...On some K-5, there sit a few dust-sized particles of 30 µm - 50 µm size on top of the cover glass of the sealed CMOS chip.

There is a smaller but finite equal chance that the stains sit within the CMOS chip on the inner side (underside) of the cover glass, or on the bottom of the AA filter, resp.

Smaller particles probably would remain invisible. Larger particles are uncommon for dust. Even 40 µm is large. Typically, dust particles are between 1 µm and 20 µm. It may actually be particles other than dust.

I follow your resoning that the spot must be formed by a round or near round (spherical) object.

Dust is not really anything scientifically well defined (such as necessarily being larger than 1 micrometer). If we are considering a former air borne object that settled on the sensor (or sensor glass or filters) we are talking about aerosol particles. But there are a few strange things here.

-Dust of these sizes we might call coarse mode particles. They deposit from the air mainly by gravitational settling (they fall down). In an air flow they will also impact on surfaces, or intercept on obstructions. At 20-40 micrometer the deposition is so efficient that they will have very short residence time in the air, and will not be able to travel very far from their source. We are talking minutes here to perhaps an hour. These properties also mean that they are fairly simple to filter away from a clean room environment. It can be much more difficult to get rid of smaller particles. So it is somewhat strange that a clean room at Pentax or Sony would fail in this way.
-Particles of this size is rarely spherical (or disc shaped). Small particles from nanometers up to the accumulation mode (0.1 to 1 micrometer) can be good spheres since some of them form in the air from condensing vapors (e.g. sulphuric acid, amonia etc), but they don't grow larger than about 0.2 micrometer at any reasonable vapor pressures. Coarse mode particles can consist of chrystals (sea salt, minerals), fibers from various often organic material, bacteria, pieces of biological material (usually far from spherical) etc. A salt chrystal will become a droplet (a sphere) if it takes up water, but this requires a humidity above about 40%. If you spend time watching aerosol particles in an electron microscope you realise that round particles are indeed rare.
-In absence of air flows with only gravitational deposition taking place, particles will fall downward. Handling the sensor in a vertical position or upside down will very much protect it from particles of this size.

All this together makes it unlikely that these round objects you have observed are former air borne particles that appear on the sensors due to an imperfect clean room environment.

...With reversed lens macroscopy, we should be able to get a very good photograph of the particles.

...The trick is to mount a, say '50 to the K-5 and a '300 to another camera like a K-7. Then use a reverse filter ring and step rings to connect the two filter rings and cameras.

And then photograph the K-5 inerds (in bulb mode) using the K-7. The '50's focus wheel is used to shift the subject plane to the required location where everything above the sensor surface is easily adjusted.

Because the entire is sealed from light, you have to place a small LED with battery (gift shop article) in the bottom of the K-5 mirror box before mounting the '50.

In the end, you get a 1µm resolution image of the particle making it about 40x40 pixels large. So, a Raynox image is 1/50 of what's feasible with equipment on board.

This is pretty cool, might try this. But I'd apprechiate if you could explain how you get to the 1 µm resolution. The macro ratio you get with with the lenses arranged like this is 6:1, right? So is the resolution at 1:1 6µm? Is that based on pixel size? Doesn't lens resolution matter?

...
...40 µm is pretty large though. I wonder why his macro shots didn't get better. In 1:1, a stain should be nearly 10 pixels wide...

So 4µm per pixel? Close enough to 6.

...
...Whether to call it dust or not ...
I agree that it is probably remaining whatever from maybe what was meant to be a cleaning procedure or peeling off a protective adhesive. But in the end, dust is what we call 10µm-scale particles sitting at unwanted places

So, what I say is particles rather than dust actually.

Has anyone else noticed the coincidence that a lot of these reports indicate a row of dust spots. There are some single spots, some with 2 spots, 3 spots, but above that there is a linear nature to the spots.

Also, we aren't seeing hairs, or cotton lint or misc. dirt. I think what this might mean is that these parts were assembled in a "clean room"...

...Almost every case reported so far have the stains or particles at or near the center so it's not some random locations.

I think this again speak against these spots being deposited aerosol particles. They should distribute rather randomly.

Falcon, could the round objects be some sort of material impurity instead? On/in sensors, glass or filter? I was thinking perhaps bubbles in the glass...bubbles makes fine spheres. And they are round and opaque. And they can appear in groups or lines if they formed together before the glass solidified.


Now we can only wait for some threads complaining that "they should have kept the Samsung sensor"

And be sure Hoya/Pentax and Sony currently have a rather vivid argument on whom to blaim (while sharpening their tantōs).

[falconeye]

Douglas,

I agree that true dust is rather unlikely. except maybe if deposited from a tool.

I say particle of coarse level dust size and I don't actually know what it is.

The obstructions don't have to be perfect disks. But they aren't very irregular either.

If they are imperfections in the glass, I would expect some refractive effects like a bright center except from an Arago spot, or Newtonian rings.

The most worrysome possibility is particles evaporating from a hot ceramic package (condensing on the inner side of the cover glass).


Wrt the macro photo:

It is 6:1. It is indeed limited by the resolving power of the 50. I tried this with a Zeiss 50/1.4 at f/4 and could resolve near to 1 micron. Of course, you only see the 1/6 center part of the sensor. A smaller macro factor like 3:1 may be easier to handle. It should resolve 5/3 micron where 5 micron is the K-7 pixel pitch.

[creampuff]

This issue is likely to be originated from Sony when they first produced the sensors. Pentax merely buys them off the shelf. I would expect Sony to pony up the replacement sensors for Pentax shortly. Do a search of Sony sensor recall and you'll discover they had to recall plenty of cameras due to faulty sensors.

[bobmaxja]

Sony reccall on CCD noting in CMOS

[secateurs]

I agree that true dust is rather unlikely. except maybe if deposited from a tool.

You'd have to be a real tool to put dust on a sensor in a cleanroom. Seriously, i very much doubt Pentax or Sony would employ such a person. I think we can safely disregard this one

oh, wait... you said "from" a tool, not "by" a tool.....

[WerTicus]

id think these sensors are put together by machine not hand....the micro lens layer for example needs to line up to the pixels exactly.

[2form]

The most worrysome possibility is particles evaporating from a hot ceramic package (condensing on the inner side of the cover glass).

Are you referring to the manufacturing process or a possible effect created by operating the camera? It worries me that these stains seem to be occurring in the center or the sensors as apposed to the edge where it might run a little cooler. Ive been given the all clear by my supplier that the sensor is clean and I'm welcome to test it before purchase. I'm hoping that these stains are not a result of camera operation.

Must be numerous K5 users with originally clean sensors that have clocked up a few video hours by now.

[benjikan]

Regardless, it was Pentax's responsibility to catch the QC issue before sending it out.

Exactly my point earlier. This is totally unacceptable.

[falconeye]

id think these sensors are put together by machine not hand....the micro lens layer for example needs to line up to the pixels exactly.

The filter assembly is glued on top of the chip after it is soldiered onto its PCB, thereby making a seal. Most probably by hand. The glue is around the border. The cover glass remains free building a .2mm gap to the filter assembly.

microlens array and bayer filter are mounted to the cmos when the cmos is packaged into its ceramic housing. In a clean room and likely by machine. But everything is inside the chip when Pentax receives it.

Which is why it is so important to know if the stains are on the inside or outside of the chip cover glass.