colour

If you print photos (on photo paper) then you use the dye-based black (denoted K often times I gathered) instead of the pigment-based black (Bk). Now when does this "photo black" actually get used? Is it only for the parts of the photo where it is completely black ("true black")? Or does it also...

When I rebuilt my printer after fitting my Potty, the nozzle check and first prints were as perfect as before. Then I decided to do a A3+ (SuperB) print and noticed horizontal banding. It seems to be getting worse with every print. Attached are the new nozzle checks on both plain and Oyster...