Does dpi affect color gamut?

[darlingm]

(Epson 9900)

I've always been printing at the max dpi, with high speed off, and finest detail on.  Finally spending some time to see where I am OK compromising.

Occurred to me that since dpi (droplets per inch) refers to how many x & y coordinates there are for the print head to target, and that the Epson 9900 uses variable droplet sizes, that color gamut might be affected when lowering the dpi, if the number of droplets that can be printed to represent one pixel is lessened.  Is this the case?

I'm really only concerned with a (trained) human eye noticeable gamut difference, rather than saying there's 0.05% more gamut on higher dpi's.

[Schewe]

Occurred to me that since dpi (droplets per inch) refers to how many x & y coordinates there are for the print head to target, and that the Epson 9900 uses variable droplet sizes, that color gamut might be affected when lowering the dpi, if the number of droplets that can be printed to represent one pixel is lessened.  Is this the case?

Epson does not use variable droplet sizes when printing at 2880 on the 9900...it uses only the finest size. So, I don't think you need to worry about it.

[Wayne Fox]

Finally spending some time to see where I am OK compromising.

Seems pretty easy to test.  Print some stuff and compare them.  I would venture to say gamut differences would be negligible - maybe slightly measurable but even going to 1440 I don't think you'll see much change in gamut.  even image quality at 1440 on anything other than very good PK papers would be very difficult to see.

Only you can determine how much "compromise" you are willing to live with.

[darlingm]

Epson does not use variable droplet sizes when printing at 2880 on the 9900...it uses only the finest size. So, I don't think you need to worry about it.

Quite possible there's no need to worry about it and that there's not a noticeable difference.  It would seem to me like printing a given pixel in mode 5 2880x1440 that always uses the finest size droplets would give more flexibility in combining the different ink colors, than if it printed the same given pixel in mode 3 720x1440, which might have to use larger droplet sizes and less total dots per pixel.

[Ernst Dinkla]

(Epson 9900)
Occurred to me that since dpi (droplets per inch) refers to how many x & y coordinates there are for the print head to target, and that the Epson 9900 uses variable droplet sizes, that color gamut might be affected when lowering the dpi, if the number of droplets that can be printed to represent one pixel is lessened.  Is this the case?

You also have to take into account that when larger droplets are used there still is the possibility to add the minimum droplet size to give the right ink amount (color strength) needed, say 3 large droplets + 2 small droplets can have the same effect as 17 small droplets. The same for diluted color inks, a larger Light Cyan dot can replace some small Cyan dots. There are several factors that may counteract one another when small droplet quantities are exchanged by fewer large  droplets. Bleeding should in theory be higher with smaller droplets as the dot circumference to dot area ratio is higher with many small droplets than with fewer large droplets. On the other hand the ink may be more solid when it hits the paper with small droplets than when larger droplets are fired, drying in the gap so to speak. Drying times on the paper can be different too. Placing of larger droplets is usually more accurate than with smaller droplets. Subtractive mixing is influenced with dot sizes and the choice for straight or diluted color inks.

With that knowledge the engineers can work out counter measures. The media preset in the driver can have compensation curves that come into action when higher or lower print resolutions are selected so for example one profile can be used for more print resolutions. In the past different profiles for different resolutions was a common approach which indicates that there were gamut differences between resolution choices then. For example Bill Atkinson's 1440 and 2880 dpi profiles for some Epson papers used on the 9600.


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[digitaldog]

This should have no role on gamut IMHO. I've printed targets at various output resolution options and find the measurement and thus profile (and gamut) are the same. Customers routinely print with the same profile and differing print res settings.