Chazs wrote:
Is this a dirty CCD, and can it be safely cleaned?
How does a dead pixel show up? Black dot, or white dot?
Yes, that's what dust on the sensor looks like (the 1D has a CCD, all other Canon DSLRs have CMOS sensors).
Yes, the sensor can be cleaned. You can have it cleaned professionally, if you like, but since this is a maintenance operation that needs to be done periodically, you might want to just get used to doing it yourself.
I'd start with trying to blow off the dust either with a bulb blower (e.g. Giotto Rocket) or with some _clean_ compressed air, e.g. www.americanrecorder.com
. Do _not_ use standard PC dust-off type products, they have propellant that can goo up the sensor. Do _not_ use the brush on a bulb blower.
If this doesn't work well enough, then you may need to swab the sensor. Look here for directions:
http://www.pbase.com/copperhill/ccd_cleaning
How does a dead pixel show up? Black dot, or white dot?
I've never seen a _dead_ pixel, though sometimes you come across "hot" pixels, i.e. a pixel that repeatably seems to display an inordinate amount of noise, particularly in long exposures. These will always show up as colored "speckles", never purely black or white, as each sensor photo site only measures one color, red, green, or blue. There are very "sharp", being individual pixels, they don't show up like blurry blobs, as in your photo, which is exactly what sensor dust looks like.
-harry