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.
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.
This comma was first named as parahemfi by Gene Ward Smith in 2005 as a contraction of parakleismic and hemififths. It is not clear how it later became hemimage, but the root of hemimage is obvious, being a contraction of hemififths and magic.