30D Dust under Filter

icassell · Jul 1, 2008

I got a piece of gunk on my sensor somehow, so I brought it in for a cleaning (I'm a bit too nervous to do more than blow on it gently with my Giotto bulb and that didn't get rid of it). The service tech got the big stuff off, but tells me that there is a fair amount of dust between the filter and the sensor that he wouldn't even try to get to -- he said the only way to get at it is to send it back to Canon and he's not sure what they'd charge ( or if they would even get it all). I'm not sure it's worth the expense, they're barely noticeable and I can clone them out.

Has anyone had this problem? What did you do?

Tyjax · Jul 1, 2008

Between the filter and the sensor? Weird-o. Haven't hear of that happening... usually the pass-filter that eliminates moire on the CMOS is smack up against or sealed against the CMOS. If it is BEHIND the filter than its going to be crazy difficult to get clean... if in fact you can verify the dust is there with a jewlers loupe than a service mail in might be your only hope. A sensor replacement can run 300-400 and if thats what you are up against maybe some electronics type dry compressed air is worth a shot... dunno.

I had gunko bunko on the low pass filter but bulbed it off after about 30 mins bulbing...

Hope you get the thing straightened. Any images with the offending blemish?

Alex_B · Jul 1, 2008

isn't the filter glued to the sensor, or at least attached really firmly so that no dust can get in easily?

i would get someone else to clean the filter glass in front of the sensor. a good wet cleaning might do it.

icassell · Jul 1, 2008

I'll find out more tonight when I pick it up. These repair guys are usually very good ... he said he had never seen anything quite like it. I'll say more when I learn more ... It's certainly not horrid enough to justify a new sensor.

icassell · Jul 1, 2008

OK. I got my camera back and talked with the tech for a while. As he explains it, the filter and the sensor are not totally sealed together -- in order to keep condensation from occurring between them. This can allow small dust particles to get between them. He says he sees this all the time, but usually to an insignificant degree. According to him, mine had more than he usually sees. He says it is more obvious when you shoot with an ultra-wide angle stopped way down due to the very deep DOF. OK, does this sound totally bogus? He cleaned the filter surface and I see nothing on my images now with my 10-20mm at 10mm, but he pointed them out on his monitor (very tiny specks). I got his usual cleaning bill of $45, so he wasn't trying to charge extra for this stuff ...

Tyjax · Jul 1, 2008

He is right about the stopped down and wide angle. Thats when they tend to show up. Especially longer exposures. If its not a problem in your images at this point I say problem solved.

And the lack of sealing to eliminate condensation makes sense in a way. Just never heard of it...

icassell · Jul 1, 2008

Well, I haven't tested things thoroughly yet, but seems to be cured for now. This was very frustrating, but I guess it's no worse than the old days when I had to make up for scratched or dirty negatives in the darkroom -- and with those I couldn't program an action ...

Tyjax · Jul 1, 2008

OK< you made me laugh. If I all the messed negatives I have trashed suddenly showed up I would have a celluloid monster on my lawn. Scratches, dust, developer accidents. Ok, I have to step outside, panic attack.

icassell · Jul 1, 2008

OMG -- I wrote it and now I have to step outside and join you ... setting up that perfect print and seeing the hair as it materializes in the bath ... no clone tool on that ole' Omega

BTW -- one outcome of this adventure was that I got rid of my camera Body Armor -- I think it is conducive to dust collection that might spill inside when I change the lens.

Miaow · Jul 2, 2008

If you want to see how much dust is actually there - the best way is to put the focal length about 50-55mm - put the aperture at/or over F22 (I tend to do it at F36) unfocus completely (put lens on manual focus go clockwise to infitity)
aim it at a evenly lit white wall (or the sky) and take a pic. The small appeture will show up all the dust.

I read an article on the net about dust and it was mentioned on a mark that was actually under the sensor filter (after they had cleaned it heaps) they were going to try and get the camera replaced (camera was pretty new) - there's no update on that site on it it actually got replaced though

icassell · Jul 2, 2008

Well, my 30D is less than a year old, but how would I ever be able to prove the stuff was there initially ...

In any event, I'm not seeing anything on the image now, although I haven't done as rigorous a test as you describe (that's basically what the tech told me to do as well, but he said to do it with the widest lens I have -- my 10mm).

Thanks, everyone. I guess I'm OK for now, but learned something here. I wish these cameras had an automatic sensor cover that came over it when you change lenses ...

Garbz · Jul 3, 2008

I wish the LP filter was removable from the front! You know you need to dismantle the entire camera to remove the sensor housing and undo the retention clip to get at those filters? Google IR conversion. It's mad that a "point of failure" if you consider dust a failure, is so hard to get to.

icassell · Jul 3, 2008

I agree. Not to mention the fact that I would love to play with IR imaging and can't afford a second body ...

Miaow · Jul 3, 2008

icassell said:
I wish these cameras had an automatic sensor cover that came over it when you change lenses ...

It does in a way - The Shutter

You usually aren't taking a pic with it open when you change the lens.

Another thing to make sure is that the chamber of the camera & mirror has no dust in/on it cause it can move back to the sensor.

I was reading somewhere that doing really long exposures can attract dust onto the sensor (not really sure on this part). Something to do with while you're taking a pic the sensor gets a charge on it so if you have the shutter open for a long time it can attract dust back.