I have a relatively new (purchased end of August) Digital Rebel which seems to have some dust or something that shows up during certain shots. For example, take a look at the sky in this image shot in London:



Luser error during shots at Stanford (spots left of Hoover Tower, exposure compensation was set low):



No spots, overcast at Chateau de Versailles:



I've cleaned my lens and tried to use a blower(?) on my image sensor (w/o touching it), but I still seem to get these sometimes. These spots happen regardless of which lens I have on the camera. Photoshop could hide the problem, but won't fix it permanently.

I love this camera otherwise.

Thanks,

-Andrew

I can't tell you what those spots are, but I can tell you that freeze spray (canned air) can damage the CMOS...don't do that. Use a spec grabber to pull lint and dust off of the CMOS.

What aperture are shooting at? The smaller the aperture the more any dust on your sensor will show up, shooting wide open you will notice it more.

Originally Posted by patch29 What aperture are shooting at? The smaller the aperture the more any dust on your sensor will show up, shooting wide open you will notice it more.

f14. I don't think that's it.

Intuitively, dust on the sensor would result in underexposed spots, right? They would be lighter than the rest of the image. These spots are dark, which implies overexposure. Or am I missing something?

Originally Posted by fish f14. I don't think that's it. Intuitively, dust on the sensor would result in underexposed spots, right? They would be lighter than the rest of the image. These spots are dark, which implies overexposure. Or am I missing something?

Underexposed on a digital sensor = dark, since it has received no light. Think of it as shooting slide film, if you underexpose it will be black. It is opposite negative film.

f14 would easily do it. I can start to see dust much easier starting at f/11 to f/22 etc.

From how I understand it the light at a smaller aperture is much more focused. The more you close down the greater definition of the dust will be in the final image.

Originally Posted by patch29 Underexposed on a digital sensor = dark, since it has received no light. Think of it as shooting slide film, if you underexpose it will be black. It is opposite negative film.

ah...got it. thx.

thanks for the info, I'll get a spec grabber and see if that helps.

(I was using the brush blower thing that came with my cheap lens cleaning kit I got at Wolfe. I took care NOT to touch the sensor with the brush. probably didn't really do anything anyway)

Dust on the sensor, expecially visible on sky shots. It takes some practice, but cleaning the sensor is necessary. Dpreview site and Rob Galbraith's both have instructions for how to clean the sensors.

Fish is very correct about staying away from canned air to clean out the dust, it can definitely damage the sensor. You will reduce dust contamination by being aware of the environment when you change lenses and try to keep the camera body as clean as possible.

Deacon

How to clean your sensor

Another point of view