There are many options in today's digital world when selecting the right media for your wide format inkjet backlit application. Understanding your application needs, and the differences between substrates, is key to selecting a backlit media that will make your signage radiant.
One of the main points to understand is the 'visual temperature of a material. The 'visual temperature' can fall anywhere on the spectrum between cool and warm and is determined by the amount of blue (cool) or red (warm) undertone the material has. This is also often referred to as the "white point". 'White point' specifically indicates the level of blue within the film. The more blue, the cooler the white and the "whiter" it looks. The higher the level of red within the film, the warmer and more yellow the film will appear.
When determining the visual temperature, you can look at the color index of a material to see where on the spectrum the media falls. The color index is simply a numerical expression that determines the color of an object. As a printer, you will see this in the graphic files when selecting or adjusting a color. You will see it depicted in a L, a, b format. (see figure 1.1)
- "L" stands for the "lightness axis". This indicates the amount of black-white there is within the color. 0 is black, 100 is white and 50 is middle grey.
- "a" indicates the red-green scale. The greater the positive number, the higher the red tint, the lower the negative number, the greener the tint. 0 is neutral and perfectly balanced between red and green.
- "b" indicates the blue-yellow scale. The greater the positive number, the greater the yellow tint, and the lower the negative number, the greater the blue tint. 0 is a neutral balance between yellow and blue.
In figure 1.1, the color index differences between "cool white" and "warm white" are difficult to see in a digital format such as a web article, therefore, we have used the blue in circled area of the Tekra logo as an example. With the lightness value being 49, we can tell that this is a pretty centered color depth between light and dark. We can also tell that the material is more green than it is red, as the 'a' value is 12 points below zero and the color is considerably more blue in hue than it is yellow being 46 points below zero in the 'b' value. Understanding how to read this report will help you better estimate the tone of white a material will project when backlit.
When selecting a backlit film for your wide format inkjet backlit application, you will primarily be concerned with the amount of red and blue. For a whiter appearance, you will want the 'b' value to have lower negative value and for a warmer appearance, you will be looking for the yellow to have a higher positive value.
"Cooler, whiter white" is preferred in retail signage that includes skin tones such as cosmetics. It is preferred in menu boards