Strange spots appearing on images

I have noticed that sometimes I get strange black blobs appearing in the same place on some of the photos that I take. Sometimes those blobs will appear and sometimes they will disappear. After further investigation, they appear when I have the camera on f/36, but disappear when on f/5.6. Does anyone have any ideas on what I can do to correct it? I have Canon EOS 350d and a kit lens. I have been using the AV mode.

Thanks

You probably have debris on your sensor (actually, on the filter that is covering the sensor).

Needs a sensor cleaning. Blobs are either dust or lubricating oil on the sensor. May not appear at wide lens aperatures, will show at small aperatures.

Post a sample to confirm.

Damn Skip! Beat me to it.

Thanks for the replies. Would I need to find an empty squeezy bottle with a hole, or can I just use the sensor cleaning thingy?

I would start with just using a rocket blower to see if it is dust that can simply be blown away.

you need to clean the sensor !!

Do a search for sensor cleaning. It's easy but you don't want to go off half cocked and need a new sensor assembly.

-F

Try
LENSPEN Lens Pen Sensor Klear or
arctic butterfly

Thanks for the replies everyone. I will try to clean the sensor once I get some of the stuff. Nearest camera shop is about 20 miles from here, so when I get the time I will pop in there and get some cleaner.