Hemimage comma
| Ratio | 10976/10935 |
| Factorization | 25 × 3-7 × 5-1 × 73 |
| Monzo | [5 -7 -1 3⟩ |
| Size in cents | 6.4789995¢ |
| Name | hemimage |
| Color name | sz3g3, Satrizo-agu comma |
| FJS name | [math]\text{dd3}^{7,7,7}_{5}[/math] |
| Special properties | reduced |
| Tenney height (log2 nd) | 26.8387 |
| Weil height (log2 max(n, d)) | 26.8441 |
| Wilson height (sopfr (nd)) | 57 |
| Harmonic entropy (Shannon, [math]\sqrt{n\cdot d}[/math]) |
~2.57607 bits |
| Comma size | small |
| S-expression | S282 × S29 |
| open this interval in xen-calc | |
The hemimage, 10976/10935, is a small 7-limit comma measuring about 6.5 cents. It marks the difference between a classic diatonic semitone (16/15) and a stack of three septimal major thirds (9/7) octave reduced, or between a classic whole tone (10/9) and a stack of three septimal third tones (28/27), therefore interesting to those who work extensively with third tones. It is also the difference between 245/243 and 225/224, the two simplest commas to define the 7-limit magic temperament.
Temperaments
Tempering out this comma alone in the 7-limit leads to the rank-3 hemimage temperament. See Hemimage family for the rank-3 family where it is tempered out. See Hemimage temperaments for a collection of rank-2 temperaments where it is tempered out.
Etymology
This comma was first named as parahemfi by Gene Ward Smith in 2005 as a contraction of parakleismic and hemififths[1]. It is not clear how it later became hemimage, but the root of hemimage is obvious, being a contraction of hemififths and magic.