TF SNR - Transfer Function - CTF correction, using frequency dependent SNR

PURPOSE

3D CTF corrects a volume series by Wiener filtering using frequency dependent SNR. Rarely used, may be buggy. Further info on CTF related operations in SPIDER.

SEE ALSO

TF CTS	[Transfer Function - CTF correction with SNR, image/volume]
TF C3	[Transfer Function - Generate a straight, complex, CTF correction volume]
CTF FIND	[Contrast Transfer Function - Estimation of CTF parameters]

USAGE

.OPERATION: TF SNR

.TEMPLATE FOR IMAGE FILES: img***
[Enter template for file series to be restored.]

.FILE NUMBERS OR SELECTION DOC. FILE NAME: 1-10
[Enter file numbers. The file numbers can also be read from a selection document file where file numbers are contained in the first register (not the keys).]

.TEMPLATE FOR CTF FILE: ctf***
[Enter template for of file series containing CTFs for respective images. The CTF files must have the same numbers as corresponding defocus groups (image files).]

.SNR TEMPLATE: snr***
[Enter template name of Signal-to-Noise Ratio document files.] The SNR files must have the same numbers as corresponding defocus groups (image files).]

.RING WIDTH: 0.5

.FACTOR APPLIED ON SNR (0.5, 1, ...)': 1

.OUTPUT FILE: MOL003
[Enter name for 3D output file.]

NOTES

1. Input files can be either real or Fourier format. CTF files must be in Fourier format. All files must have the same dimensions. Output file is real.

2. CTF functions can be generated using 'TF C3'. All parameters have be determined using 'TF ED' and 'TF EA'.

3. Implemented by L. Joyeux.

4. EXAMPLE: 3D reconstruction process, CTF correction part

    
      ; Create SSNR functions from FSC  
      DO [grp]=1,[last] 
         SN RB [pass],[stop] 
           final/dres003 
           l 
         SN RF 
           [pass],[stop] 
           37 
           0.1, 0.98 
           2 
           snr003_{***[grp]} 
      ENDDO 
      ; CTF correction using SNR (function of FSC) 
      TF SNR 
        ttvol004 
        1-[last] 
        ctf*** 
        snr003_*** 
        0.5 
        1 
        tvol004 
   

SUBROUTINES

TFSNR

CALLER

UTIL1