Permanent sensor dust spots - what is Canon's manufacturing specification?

I had recently returned my 5D3 to Canon due to permanent sensor dust spots (8 spots) visible at f22 to f8. Canon service confirmed that the spots cannot be cleaned externally and were internal to the sensor. Canon replaced the sensor and upon receiving the 5D3 back, I was surprised that there was still one spot visible at f22 to f16. This spot was also confirmed to be non-removable by wet cleaning.

This makes me wonder what is Canon's manufacturing specification for dust spots on their sensor? I would think that the sensors are assembled under clean room environment and should have strict particle control.

Not sure about specification but many online reviews of canon cameras mention a new unit coming with a less than sparkly clean sensor

I have a bunch of questions...

What is a "permanent sensor dust spot"?

Why replace the sensor? Sensor dust collects on the low-pass filter on top of the sensor.

Have you tried cleaning it?

How do you know if it is permanent vs temporary? I have never heard of such a thing. If the dust spot cannot be removed, I would send it back.

Like Mike, I'd at least try to clean it. Its perfectly possible its arrived in transit.

1st I ever heard of dust under the filter.

How big / dark is the spot?
1 spot, if not too big or dark is worth putting up with IMHO

Permanent dust spots are dust spots that attach to the sensor during the manufacture process. Sensors must be built in dust free environments with very clean air and people using all kinds of protection. If they get dust spots at this point, it cant be cleaned off.

Alex_Venom wrote in post #15896570
Permanent dust spots are dust spots that attach to the sensor during the manufacture process. Sensors must be built in dust free environments with very clean air and people using all kinds of protection. If they get dust spots at this point, it cant be cleaned off.

I would hope that even one dust spot under the filter is too many. If it is there from the manufacturer, I would think that at the very least, it should have mapped out and you would have never known about it.

The one you see now, how do you you it is "permanent"?

I have heard of people having problems with dust between the sensor and the AA filter. This is most likely to happen during manufacture and, if it happened to me, would result in the camera being returned immediately. I can understand dust on the filter when purchased, but that's easily fixable. Between the sensor and the filter is a totally different matter.

Frank,

I do wonder if that's what the real problem was and Canon simply failed to correct the OP's misunderstanding of the true situation?