[argyllcms] Re: Feature request (and an implied question)

  • From: "Hal V. Engel" <hvengel@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 27 Jul 2010 09:58:12 -0700

On Monday 26 July 2010 09:14:24 pm Ben Goren wrote:
> Hmmm...as I understand it, for any given illumination level and ISO, there
>  is exactly one corresponding EV (and vice-versa). One may, of course,
>  choose to expose the film / sensor at a different EV, but that would be
>  akin to a musician intentionally playing a note out of tune for dramatic
>  effect. Therefore, from my understanding, EV is every bit as much a
>  measure of light level as scale notes are a measure of audio frequency.
> Also, at least in my experience, whenever ISO is omitted from EV, it's
>  assumed to be ISO 100 (just as musical pitches are assumed to be equal
>  temperament from A = 440 Hz unless otherwise specified).

Not to belabor the point but the assumptions about musical tonality are not 
correct.  Only some instruments are equal temperament by design (most 
keyboards but not much else) most others and vocalists can bend their pitch 
and will use just temperament (or just intonation) meaning that they adjust 
the pitch of each note until it resonates with the other parts of the current 
harmony.  Think barber shop quartet. 

This means for example that thirds are pitched lower by about 14 cents and 
fifths are pitched higher by about 2 cents than they would be if the 
temperament was equal.   Notice that this implies that the pitch of a given 
note depends on it's musical context as the harmonies of a given piece of 
music change.  For example the C in a C major cord (where it is the root of 
the cord) will have a different pitch than the C in an A major cord (where it 
is the third of the cord and will be 14 cents lower) and this will be different 
from the pitch of C in an F major cord where it is the fifth of the cord.   
Most wind and string players will (if they are listening) use just intonation 
naturally since the pitches will lock in and are easier to find.  Also being in 
a band I have to sit through regular lectures by the music director about this 
and he insists that we use just intonation.


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