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How anyone can own a DSLR and not know how to clean it is beyond me. It's very simple, very inexpensive, and there are countless instructional threads here on FM and the 'net. Buy yourself the appropriate supplies, learn the task, and continue to enjoy the great 5Dc. In most cases all you'll need is an occasional blast of clean air from a Giottos Rocket Blaster, but first you need to start with a properly cleaned sensor. Sounds like your 5Dc sensor might need a good "wet" cleaning. Here's a push in the right direction:
Thanks. For some reason, I remember reading somewhere a while back that it wasn't advised to clean your camera sensor (due to possible damage) by yourself and that it should be done professionally. So I never attempted to do it myself. After reading some DIY tutorials and watching some YT videos, however, I feel sheepish now. It seems pretty easy to me and relatively safe as long as you follow proper procedure. I guess I could've saved a bunch of $$$ over the years... Oh well, better late than never.