Epson TM-L90-i Technical Reference Manual page 40

 Transparency rates are measured by the Macbeth TD-904 (with a filter for infrared) pho-
 If the transparency rates are out of the specified range (label + backing paper: 18% or
40
tometer. The transparency rates are calculated as follows:
Use
Density = Log10 (Amount of irradiation / Amount of transparency)
Then,
Transparency rate (%) = (Amount of transparency / Amount of irradiation) x 100
less, backing paper: 47% or more), the printer detects a layout error. However, paper
identified with a layout error may be used when the detection hole is prepared as follows.
The position to detect the label may be shifted by approximately 0.5 mm {0.02"}.
1.75±0.5
Corner R0.5 or less
6±0.5
8.0±0.1
Corner R2 or less
0.5±0.3
5.0±0.5
0.5±0.3
Face (printed side)
Detection hole
Units: mm