Measurement scales and thresholds
Measurement scales reveal the proportion between a given measurement and its parent value, font value, or default value.
Measurement scales
Parent scale
The p-scale (A÷B) is the scale of a font-level measurement (A) in relation to its parent measurement (B).
Example:
| ref. | description | name | glyph | source | value |
|---|---|---|---|---|---|
A |
font-level measurement | XOLC |
n |
current | 170 |
B |
font-level measurement | XOPQ |
H |
current | 180 |
A÷B |
p-scale | 0.944 |
“The general thickness of lowercase vertical stems is 94,4% of the general thickness of the uppercase vertical stems.”
Font scale
The f-scale (A÷B) is the scale of a glyph-level measurement (A) in relation to the font-level value of the same name (B).
Example:
| ref. | description | name | glyph | source | value |
|---|---|---|---|---|---|
A |
glyph-level measurement | XOLC |
u |
current | 168 |
B |
font-level measurement | XOLC |
n |
current | 170 |
A÷B |
f-scale | 0.988 |
“The thickness of a vertical stem in u is 98,8% of the general lowercase vertical stem thickness, which is taken from the n.”
Default scale
The d-scale (A÷B) is the scale of a font- or glyph-level measurement (A) in relation to the same measurement in the default font (B).
Example:
| ref. | description | name | glyph | source | value |
|---|---|---|---|---|---|
A |
glyph-level measurement | XOLC |
u |
current | 586 |
B |
glyph-level measurement | XOLC |
u |
default | 168 |
A÷B |
d-scale | 3.488 |
“The thickness of a vertical stem in u is 348,8% thicker than that same stem in the default font.”
Measurement thresholds
Each measurement scale has a corresponding threshold value which can be used to validate a measurement against a reference value in the same font or in another font.
| scale | threshold | validation against |
|---|---|---|
| p-scale | p-threshold | parent font-level measurement |
| f-scale | f-threshold | font-level measurement |
| d-scale | d-threshold | default font- or glyph-level measurement |
Measurement validation
Based on its threshold value, a scale can be in one of three value ranges in relation to its reference value.
Each value range can be represented by a different color, allowing visual validation in tables with multiple scales and measurements.
| range | color | meaning |
|---|---|---|
| equal | blue | equal to the reference value |
| within | green | different from the reference value, but within the threshold for this scale |
| beyond | red | different from the reference value, and beyond the threshold for this scale |