The traditional vision of a 1D barcode seen on supermarket shelves is a rectangle that is composed of black vertical lines on a white background with various indecipherable numbers underneath. It looks pretty boring and so it has become very much invisible to the shoppers eye unless they need to pass it to the checkout clerk for scanning. The fact is it wasn’t meant to attract attention. It should not compromise the overall presentation of the commodity it is selling. So why would you want to add colour to barcodes? Surely the barcode begins to attract attention in its own right then? Surely this cannot be good for the product?
Optimum contrast – optimum performance
The monochrome appearance of the barcode label was designed not so much to be unattractive to the eye as to be attractive to the barcode scanner. For a scanner to work at optimum performance there must be substantial contrast between the foreground and background of the label. The two colours at either end of the spectrum are black and white and so they will always provide the greatest contrast. However manufacturers and retailers have found that sometimes, often due to the colouring of the product itself or some other variable there is a need to colour the barcode. It is then important to get the contrasts on the label correct.
Using colours to enhance contrast in a barcode
A rule of thumb is – if the colour difference appears to be marginally safe – that is not enough. You really need to go for swatches that have a substantial contrast. The best contrast is obtained when the background reflects all the light and the bars reflect none. This is never fully achieved in practice but there must be a significant difference between the bars and background if the code is to be read reliably. In the barcode world you are looking for a good SC or symbol contrast. The optimum SC is (Rmin) light reflectance value is subtracted from the minimum reflectance value and shown as a percentage. In this way the Rmin is the colour of the bars and the Rmax is the colour of the background.
The optimum threshold is 40% to create an ANSI/ISO C grade. If you can reach an SC of 70% you have a pretty safe level.
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