Under exposure causing dust spots?

[Jackie Matthews]

I've recently done a lot of landscape shooting and whilst editing the files, I noticed a lot of dust spots on the images so I sent my camera for cleaning.  My husband collected the camera and the shop assistant said that the camera was actually already quite clean but he'd cleaned the sensor etc anyway.  He did ask my husband if any of the images I was editing were underexposed as he thought that this could cause this issue, ie, dust spots on the images

I've just taken some more shots this morning and whilst editing, I can see almost the same spots on the images as before. 

The file that I noticed it in was probably a little underexposed so I tried to find an image where the exposure was a little better and there seemed to be no spots visible in the images (I use a plug in by Greg Benz, he has a luminosity masking panel and this has a dust spot finder).  Editing out the dust spots is very time consuming

So I guess what I'm asking is, is it the underexposure causing the 'dust spots' on the images and if so, how?

I've also asked Kim for her advice on her forum page but any input would be welcomed

Thanks

[Brian]

Can you post a photo? 
 

if your sensor has been “cleaned” the only thing I can think of is you have dead pixels in your Camera’s sensor. Usually it’s when you set your Aperture to f/16 and shoot something bright / clean will you see dust spots. I’ve never heard of underexposure causing this issue. 
 

Also, try using a different lens just for giggles. You might get lucky and find out the problem is with the lens. Especially Zoom lenses. Usually I will get a response, “...but I never take the lens off!” If it’s a zoom, sometimes dust can work its way in the control rings when you zoom in and out. Especially if you are in dusty areas, like the beach or in a desert. 

[Jackie Matthews]

I've posted these images to Kim too for her advice

 

1) sliders in acr showing a well exposed piece of paper taken with a macro lens f32

2) visualise spots in acr

3) a stamp visible layer created using the luminosity panel I use for spot/dust removal

4) a 100% crop of 3 above

5) a 100% crop of the image of 3 above

The image here was taken with a different lens to the one initially found the issues with and this is after the sensor clean

 

Any advice would be welcomed

[Brian]

Yeah...contact Canon. You have a bad sensor. That's not dust and I'm seeing some "Banding" on the left side with one of the photos.

No, you can't fix or clean your way out of this one.

Contact Canon and schedule a repair with them. The sooner the better.

Also, a quick Google Search yielded other people with this problem.

[Jackie Matthews]

Oh gosh, ok thanks for your help anyway