Re: L* to Density equation (matt louis)
Re: L* to Density equation (matt louis)
- Subject: Re: L* to Density equation (matt louis)
- From: Samer Mady <email@hidden>
- Date: Fri, 29 Jun 2001 09:52:37 +0200
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Message: 5
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Date: Thu, 28 Jun 2001 11:28:44 -0500
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To: email@hidden
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From: matt louis <email@hidden>
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Subject: L* to Density equation
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Does anyone know an equation to calculate L* to StatusT density?
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Thanks,
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Matt Louis
L* = 116 * f( Y/Yn ) - 16
Yn : XYZ_Y of white point, Y : XYZ_Y of the sample
f( x ) = x^(1/3) if x>0.008856
f( x ) = 7.787 * x + 16/116 if x<=0.008856
in order to calculate from L* back to Y we have to exclude the
second possibility. we can do that since the second possibility ( Y/Yn
x<=0.008856 ) happens only wenn the XYZ_Y of the sample is 0.8856 or less
than that. and is seldom the case
=>
Y = ( ( L* + 16 ) /116 )^(3) * Yn
the density is log( 1/R ) R = reflectance i dont think that it is
possible to calculate the reflectance from the XYZ_Y value. so we have to
calculte the density using the XYZ_Y value insted of the reflectance
=> D = log( 1/( ( ( L* + 16 ) /116 )^(3) * Yn ) )
samer mady