Dark spots in the sky - help with problem please..

I hope this is the right place to post this and sorry if it has been posted before. I did a search but couldn't find what I was looking for.

I have a problem with dark spots which show particularly on blue skies. They do not always appear, and only show with the kit lens (18-55). The camera is the 350D/Rebel XT.

Any help/suggestions appreciated.

dust on the sensor..get a rocket blower or something like it at a local camera store and give it some blast of air..dont use air in a can though

A rocket blower can help but you may have to go to a different method of cleaning your sensor. I use a wet method. Do a search and read up on them. It is not to hard. I used the blower once and it blew dust up on to my viewer screen. This does not afeffect the picture but I see dust specks every time I loook thru the viewer. I also have the 350D.

Thanks - but if it's on the sensor, why does it only appear with one particular lens? When I change to another lens I don't get the same thing...

You'll see the sensor dust at higher f-numbers. This photo was at f/14.

See pages 39-40 of the XT/350D manual for camera-specific information, and cleaningdigitalcameras​.com for general information on sensor cleaning. (There is a ton of info on the Web about cleaning your sensor, but that site pretty much covers it all.)

Yup, looks like sensor dust. XTi has a dust delete data setting in it. Don't know if 350/XT does though. Worked quite well on my XTi. Higher number f stop's and blue sky was the worst to show sensor dust.
Cleaning sensor advice above is the best solution. Also if you have PSE or better, you can clone it out on pics you already have.
Hope this helps,
Ron

Thanks guys - I shall follow the advice and let you know!