Paper Paper on the Wall Drop 2 - part 5 of 1 2 3 4 5

by Mike McNamee Published 01/04/2013


* Interpolation is a mathematical process which examines the surrounding pixels to a particular location in a file and then invents new pixels which attempt to preserve the detail structure of the image. In non-mathematical terms it has a peek at the pixels around itself and then takes a stab at what the colour of the new pixel should be. Thus if it is surrounded by green pixels it will make the new pixels green but if one side of the area is turning red it will make the new pixels towards that are a shift towards red. This is, of course, a very simplistic description but it is roughly the way it works.

This was effectively a run off between the HP and Epson Technology using the same media but different RIP solutions (Onyx with HP, ColorGATE with the Epson).


Using our standard 216 patch target the average errors on both machines was good, the Epson just having the edge. For the record the data are tabulated.

The major contribution to error in the HP-Onyx solution came from the lightness channel which was consistently too light but also highly variable. Both skin tone sets were good, the Epson spectacularly so with an average error of 2.82ΔE00 but with a zero error in hue.

As might be expected from the greater range of inks, the gamut of the Epson was demonstrably higher and although we did not have gamut volume measurements the HiGAM error statistics showed the better handling of saturation (DC/w value). The yellow-greens, yellow and oranges were much superior from the Epson ink set.

The overall smoothness of the Epson result was superior; there was less banding, tighter variation in the solid tones and smoother detail in the skin tones. The Grainger Chart was particularly telling being quite lumpy from the HP and very much smoother from the Epson.

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