RF SN - Spectral SNR of images ||

PURPOSE

Compute the Spectral Signal-to-Noise Ratio (SSNR) of a given series of images.

SEE ALSO

RF	[R Factor ||]
RF 3	[Phase Residual & Fourier shell correlation, 3D ||]

USAGE

.OPERATION: RF SN

.ENTER TEMPLATE FOR IMAGE NAME: IMG***

.ENTER FILE NUMBERS OR SELECTION DOC. FILE NAME: 1-700 OR SELECT
[Enter projection file numbers or the name of the document file containing projection file numbers in the first column.]

.MASK FILE: MAS999
[Enter the name of mask image for masking each image in the set]

.RING WIDTH: 0.5
[Enter ring width of each frequency radius for SSNR computation.]

.DOCUMENT FILE: DOC001
[Enter name of resulting document file.]

FR(I) = N*{SUM(SIG(kX,kY))/SUM[NOI(kX,kY)/(N-1)]}
Sum over Fourier units in each ring of radius I

NOTES

1. If you do not want to mask the images, you still have to create a mask image with constant value 1 by using command 'BL'.

2. Command calculates the following equations:
   SSNR: SSNR(I) = FR(I)-1 if FR(I).GT.1
   = 0 if FR(I).LE.1
   VAR(I) is the expected variance of SSNR(I):
   VAR(I) = SQRT{2[(N2+N1-2)*(1+2*SSNR(I))+N1*SSNR(I)**2)]/ [N1*(N2-4)]}
   --- N1 = NRING(I)/2
   --- N2 =N1*(N-1)
   --- NRING = Number of Fourier units for each ring.
   DOC file: COLUMN: #1 #2 #3 #4 #5
   RING RADIUS RING RADIUS SSNR(I) NRING(I) VAR(I)
   (NORMALIZED SCALE)

3. References:
   [1] M. Unser, B.L. Trus & A.C. Steven, Ultramicroscopy 23(1987) 39-52: "A New Resolution Criterion Based on Spectral Signal to-Noise Ratios"

   
   [2] M. Unser, B.L.Trus & A.C. Steven, Ultramicroscopy 30(1989) 429-434: "The Spectral Signal-to-Noise Ratio Resolution Criterion: Computational Efficiency and Statistical Precision"

SUBROUTINES

SSNR, SSNRB

CALLER

FOUR1