Specifications

The Digital Fine Print Course

Viewing a Fine Print

Ink Inconstancy

Ink inconstancy is where the relationship between colours alters, sometimes drastically

when a CMYK print is viewed under different lighting conditions. This is different to the

overall colour shift that comes from moving the print from one light source to another.

For example, as the wavelength of light moves from red to infrared our ability to see colour

falls off gradually. But cyan dyes don’t absorb strongly in the near infrared region of the

spectrum, though we still see this radiation as reddish light. Under infrared rich light,

such as incandescent light, a CMYK print can be grey balanced so that greys appear neu-

tral by using a large quantity of cyan ink to absorb the excess infrared radiation. However

if the same print is illuminated by light that contains little infrared radiation, such as day-

light, the print’s neutral greys will no longer appear neutral. The excess cyan dye will now

colourize the print, most notably the neutral greys. and it will then take on a distinct cyan

green colour cast.

One way to minimise ink inconstancy is to use heavy GCR (Grey Component

Replacement) so that cyan is not significantly involved in the reproduction of neutral

greys. However this work around has other problems because brighter colours based on

a lot of cyan will still exhibit the effects of ink inconstancy. Also heavy GCR because it

substitutes black ink for equal CMY ink weights can produce a more noticeable inkjet dot

pattern in the print. Unfortunately many printer drivers do not provide printer CMYK sep-

aration settings, so we have little choice or control over this effect.

Some printers such as the Epson’s Ultrachrome pigment inkjet printers include addi-

tional Light Black ink(s) that facilitates increased GCR throughout the entire tonal scale,

which together with reformulated Matte and Photo Black inks significantly reduces ink

inconstancy. This is a very significant improvement in inkjet technology, especially for

fine art B&W printing where it is preferable to use 100% GCR.

A similar psychophysical effect is metamerism failure, which is not the same as ink incon-

stancy, but is often confused with it. Metamerisim failure is responsible for the excessive

green appearance of fluorescent lights (and extreme orange of incandescent lights) on

daylight film, and the ‘pink violet’ colouration when photographing certain flowers such

as Morning Glory. Silver absorbs all colours equally, including infrared, so silver gelatin

prints do not exhibit these effects. It is a problem most common to the reproduction of

grey tones and pastel colours in CMYK inkjet and offset printing processes.

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