It does only appear on small aperture .....
I read the manual if the automatic sensor cleaning doesnt remove it, should bring to service centre let the expert do it and that the sensor is very'delicate' not suppose to brush it .... donnno whether they just want to make money or we can try use brush to brush it ....
you can brush it - only with high quality soft artist brush (which some people have done) which is definitely clean - regularly cleaning it with alcohol of sorts is recommended, else you will just smear the sensor with dirt and dust and oils.
a good example of a glorified artist brush with a little spinning motor is the extremely overpriced artic butterfly.
to be honest, DIY yourself, just need blower + pec pads/sensor swabs + eclipse cleaning solution.
i don't even use pec pads, i use high quality cotton buds. started using those 2 years ago, i don't think my pictures have any problems.
everyone wants to think their sensors are tofu, need a technician to do it with "specialised equipment"? think again. you should read up on what the techs in the servicing centres do.
of course, paying the money so that you can get a new camera if the techs screw up is a form of insurance.
i don't even know how you could screw up though. i do not have the most nimble fingers.
canon/nikon/fuji/pentax/sony technicians have special powers? :bsmilie: