mandjb,
I have had the same problems that you experienced. It's called banding. Some Web research reveals a number of studies and discussion forums that show banding is not uncommon, but most clearly regard banding is an inkjet printer problem that should be unacceptable. Nevertheless there are minimal banding thresholds that people will accept ... or not even recognize.
On my new Canon printer, test print patterns and all types of cleaning display perfect printing, but subsequent photo prints are a completely different story. Printing on various types of paper — plain, heavy matt, photo paper — and selecting their corresponding printer settings have made little or no difference.
What I have found is that, depending on the paper used, there are certain combinations of Print Quality, Color Saturation, and Contrast that have to be correctly chosen to keep banding hidding to the untrained eye. And believe me, I have had quite a bit of training the past month to recognize banding.
Fortunately, many of my friends and work colleagues do not see it. Insofar as that goes, the prints are acceptable.
