Spots

[cpat]

I have a Canon 20D and within the past few weeks spots have been showing up when I take really long exposures. The spots are showing up in the exact same place in each picture. I thought it might be dust, so I tried blowing off the mirror with compressed air, but that didn't work. I've also thoroughly cleaned the lens I'm using. My guess is that there's dust on the sensor. I've only had this camera a few monthes and this is my first dSLR, so I don't know much about maintainence. If that's the problem, what's the safest way to clean it? It just seems strange to me that they only show up in long exposures. If you have any suggestions about what it could be and how to fix it I'd really appreciate it. Thanks.

I've included a picture to show you exactly what I'm talking about.
http://i35.photobucket.com/albums/d167/cpat_/IMG_3104.jpg

[timmciglobal]

What apature? Small F stop = you see dust usually.

Tim

[cpat]

Thanks, that would definitely be an issue in the pictures they're popping up in. I didn"t know that but it definitely would make sense in these pictures Thanks

[danielg]

Defintely sensor dust. Its something I hate and hopefully something that the camera mfgs engineers can invent something that can truly eliminate these in the future. but for now I guess since blowers didn't work you ned to do the wet method. If you are not comfy with it, get Canon to clean it for you :)

[D Thompson]

The spots are showing up in the exact same place in each picture. I thought it might be dust, so I tried blowing off the mirror with compressed air, but that didn't work. I've also thoroughly cleaned the lens I'm using. My guess is that there's dust on the sensor. I've only had this camera a few monthes and this is my first dSLR, so I don't know much about maintainence. If that's the problem, what's the safest way to clean it? It just seems strange to me that they only show up in long exposures. If you have any suggestions about what it could be and how to fix it I'd really appreciate it. Thanks.

If there is dust on the mirror it will show up thru the viewfinder, not on your shots. The long exposure doesn't have anything to do with it - it's the f20 on the posted shot. That's when it will typically show up, starting around f11 or so. I wouldn't use compressed air if I was you, get a blower. I'd try this to clean the sensor first. Make sure the battery is fully charged. The instructions for sensor cleaning are in your manual also. Take the lens off, go to menu and select sensor clean. The mirror will flip up out of the way. Hold the camera with the opening facing downward and GENTLY use the bulb blower several times to remove the dust. Turn camera off when done. This will work most of the time. I'd only try the "wet" method if this didn't work or take it in. Hope this helps.