I purchased the same Canon scanner - from a better dealer- about 6 mo ago and had basically the same problems. It was as if "soot" was covering the image with Provia 100 iso slide film, which normally scans beautifully. I made some inquiries of those with considerable experience with different scanners and was told the problem was with the scanner design, not my unit. I might also mention that the "Fare" dust removal did almost nothing. I sent the scanner back for a full refund, which I received.
Since then I purchased a Nikon LS-40. What a difference ! Don't believe you need 4000 dpi . You cannot tell the 2900 dpi scans with this unit from a 4000 dpi Nikon at 11x14. The ICE defect removal is superb and the GEM for decreasing grain is remarkable.
I was going to switch to digital until I got this unit -which at $875 is less than the Canon. The ICE and GEM cause no "softening" you can see unless you blow-up tiny parts of the scan to enormous size.I do not feel consumer digital capture will reach the capabilities of this scanner for 2 yrs.
The Canon scanner is either a faulty design or has horrendous quality control. In either case, I would recommend that you purchase a better scanner such as the LS-40.
Larry

: I'm not even sure where to start! Let's start at the beginning.

: Purchased Canoscan FS4000US from B&H Photo. Didn't realize that they only give you 7 days for returns/exchanges. Hardly enough time to fully evaluate your new scanner given that you have to work all day and scan in the evenings!

: Anyway, negatives scan fine (for the most part--more on that later). Of course I have thousands of slides and almost no negatives! Slides, mainly Provia 100 and Velvia (properly exposed mind you), almost always scan too dark (99% of the time). Upping the exposure in FilmGet washes out the brighter areas.

: When I use the curves or levels tool to brighten these dark scans, I get the dreaded red streaks! And LOTS of dark noise. In areas of medium to light continuous tone (any color), if you zoom in you will see the "soot". It actually looks like soot or pepper sprinkled on the image--very bad.

: One more problem I've noticed: When scanning at 16 bits per channel, whether slides or negatives, areas of white (such as snow or clouds) have numerous randomly placed pixels of pure magenta, yellow, and cyan! I have to go in and use the clone tool to remove them. It's gotten so bad that I can no longer use the 16 bits/channel. I have to scan at 8/bits (no random colored pixels at this bit depth--don't ask me why).

: I have scanned many of the same slides on a polaroid sprintscan 4000 at work and I get NONE of these problems!!! I also have no other programs running and no other devices in the same room (except for a light bulb) on while scanning.

: So I called B&H and asked for money back or an exchange. No dice! I was past the inflexible 7-day window. They suggested I work with Canon. So I pursuaded Canon to evaluate my scanner. They decided to just send me another one instead.

: Got the new scanner (in a ripped box) installed it and started evaluating it. EXACTLY THE SAME PROBLEMS!! Every problem I had before showed up on the new scanner. I asked Canon for my money back but guess what? The warrenty does not provide for a refund! They suggested I contact the retailer for a refund. I did. B&H said they could do nothing since I now have a different scanner than the one they sold me! (round and round we go)

: So Canon offered to have their senior technician evaluate my scanner. I should receive the UPS packing slip today and will ship my scanner back to Canon again tomorrow. I will keep you posted but I'm not even hopeful anymore--just disgusted (I apologize for my tone and sarcasm but I've been dealing with this for 6 months now with no end in sight!)

: I am so disappointed with Canon and with B&H (they've lost a customer for life). I feel I've been suckered into buying a substandard piece of equipment with no recourse. Oh how I wish I bought the Nikon!

: Any advice?