# Diffraction, Photosite Size, Modulation Transfer Functions

Started Apr 20, 2013 | Discussions thread
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 Re: Diffraction, Photosite Size, Modulation Transfer Functions In reply to Detail Man, Apr 20, 2013

For those who may be interesting in the mathematical identities utilized to calculate the MTFs:

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Lens Diffraction: (2/pi) * ( ArcCosine(f) - (f) * Sqrt ( 1 - (f)^2 ) )

where f is the dimensionless product of Spatial Frequency multiplied by Wavelength * F-Number.

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Photosite Aperture (100% Fill) convolved together with Optical Lowpass Filter assembly:

Absolute Value ( ( A * Sin (pi * B * f) / (pi * B * f) ) + ( C * Sin (pi * D * f) / (pi * D * f) ) )

where: A = 1/2 + Offset;  B = 1 + 2 * Offset;  C = 1/2 - Offset;  D = 1 - 2 * Offset

and f is the dimensionless product of Spatial Frequency multiplied by Photosite Aperture (100% Fill).

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Notes:

Offset of 0.250000 yields first zero response at 1.000000 times the Spatial Sampling Frequency.

Offset of 0.333333 yields first zero response at 0.750000 times the Spatial Sampling Frequency.

Offset of 0.375000 yields first zero response at 0.666667 times the Spatial Sampling Frequency.

Offset of 0.400000 yields first zero response at 0.625000 times the Spatial Sampling Frequency.

Offset of 0.500000 yields first zero response at 0.500000 times the Spatial Sampling Frequency.

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