I have access to a CcMmYyKk inkjet printer at work and it seems to my eye that results are smoother (which makes sense since there would be less halftoning going on), but also that we are able to reproduce a bit wider gamut than a regular CMYK inkjet. Blues and violets seem particularly more vivid.
Is there really a difference in gamut or is it an illusion due to some other variable? I haven’t found an example for a CcYyMmKk in the standard gamut charts found online.
Well, every printers gamut differs form other printers. But if you’re asking whether CcMmYyKk offers gamut improvements over CMYK using the same inks and device, then the answer is a that it potentially gives you slightly more ranges at lighter colors one would need to measure. But really this depends heavily on the actual implementation details of each ink.
It does however make for a more compact raster screen or maybe more accurately, stochastic screen, so in a way the printer produces sharper images despite having the same dot pitch as a comparable CMYK printer and this can make the images also appear more vivid.