Phaotic comma

Interval information

Ratio	256000/255879
Factorization	211 × 3-9 × 53 × 13-1
Monzo	[11 -9 3 0 0 -1⟩
Size in cents	0.818472¢
Names	photic comma, photisma
FJS name	[math]\displaystyle{ \text{A1}^{5,5,5}_{13} }[/math]
Special properties	reduced
Tenney norm (log2 nd)	35.9309
Weil norm (log2 max(n, d))	35.9316
Wilson norm (sopfr(nd))	77
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The photic comma, or photisma, is an unnoticeable 13-limit comma with a ratio of 256000/255879, and a size of approximately 0.82 cents. It is significant in that it is the interval separating a stack of two meantone commas from 40/39. Tempering it out thus splits 40/39 into two equal halves, each representing 81/80, leads to a form of photic temperament.