BMPCC Sensor Dust or Dust Between Sensor and Glass

I've had my pocket camera for about two weeks, and I've been using it quite a bit. Yesterday though, I tried to shoot some seagulls in flight against a blue sky. I had the camera at iso 200 and f/21 or so.

Today, I opened the footage on the computer and saw a grey blob of dust in the sky. I tested the camera some more, and even with a basic ND filter shooting at f/11 or so (again against the sky), the grey blob of dust is there. Not surprisingly, if I open the lens up to f/5.6 or f/4 the dust does not appear. I have frames saved as .jpgs with the dust speck, but I'm not sure how to upload here.

Anyway, I took my BMPCC to my local camera store to ask them what they recommended as far as sensor cleaning. Using a loupe, the guy tried to blow away the dust. However, he said that the speck was caught between the sensor and the glass covering the sensor.

I'm curious and concerned about this. Is it possible to get dust between the sensor and the glass in front of the sensor in normal day-to-day use? Like I said, I've been using the camera quite a bit, and I hadn't noticed the dust before, but it's possible this is because of the light color of the sky in the shots where I did eventually notice it.

I guess I'm curious mechanically--is the area between the sensor and the sensor glass supposed to be sealed?

I guess it's also possible that the camera store guy was wrong, and that the dust smudge is on the glass. They had never heard of Blackmagic before and had to ask me what my camera was, but I would assume that sensor housings are standard enough for them to know what they were talking about anyway. Maybe not though?

I hope I can avoid sending the camera in to be fixed, I love using it and can't say enough good things about it otherwise. But, I plan on doing birding and landscapes and kind of need apertures above f/8.

Any advice or answers are appreciated.

Hi Garrett,

There is a possibility that you could have a contaminated sensor. The only way to find out if it is behind the glass or in front is to contact BM and send it in for service. You could also frame a white A4 sheet of white paper full screen which will show up the offending object. BM might ask for you to send in a sample.

Hey thanks for responding. I guess I'll get in touch with BM customer service tomorrow.

Here is an example if anyone is interested. The dust blob starts by the #2 and the hammer. This was shot at iso 800 and f/22. Vimeo compression lessened the effect, and it's even worse outdoors. I played with the exposure a bit to try and mimic how bad it is agains the sky. The password is "speck".

vimeo.com/75456172