How high the resolution has to be
Most warehouse labels are 203 dpi and always have been. 300 dpi is
for small type and dense 2D codes. 600 dpi is for genuinely fine detail on a
small label — the sort that goes on a component or an instrument rather than
a carton.
A retail barcode is where this stops being
academic. An EAN-13 module at 100% is 0.330 mm, and a printhead can
only lay down whole dots. A 203 dpi head is 8 dots to the millimetre,
so one dot is 0.125 mm: two dots is 0.250, which is 76%, and three is
0.375, which is 114%. Nothing lands in between.
76% is under the 80% GS1 sets as the minimum for a
retail scanner, so on a 203 dpi head the answer is 114% — a
barcode bigger than nominal, on a pack that has to make room for it.
300 dpi is 12 dots to the millimetre, and four of those is
0.333 mm, or 101%. That is nominal for every practical purpose, and it
is why an EAN-13 at 100% is a 300 dpi job.
So 203 is not a barrier to selling through a retailer; it
is a different size on the pack. Worth knowing before you buy, because it is
decided by the printhead and not by the artwork.
The barcode number itself comes from GS1 —
you join, they issue it, and having it tested is between you and them. What we can
tell you is what the printer will put on the label, and whether the machine in
front of you can print it at the size a retailer expects.
It is not a setting. The resolution is the
printhead, so it is decided when the machine is bought and changing it later means
a new head. The cards above say what each machine is listed at — ask if you
need one that is not there, and the printhead list names
all three resolutions with their part numbers.
And the resolution you land on is the same number that
decides where anything sits on the label, because ZPL positions in
dots rather than millimetres — 8 to the millimetre at 203 dpi and 12
at 300. That page has a label, the code that prints it, and the arithmetic.