CM200 Magnification Calibration

Magnification Table prepared by Andrea Nans (04/2007) after objective lens change. Calibrations correspond to Angstrom/pixel for 1kx1k Gatan 794 CCD camera. Purple values were obtained using negatively stained catalase crystals and yellow values were obtained using a square diffraction grating.

Magnification Table prepared by Wanzhong He (11/13/2001)
Calibrations correspond to Angstrom/pixel for 1kx1k Gatan 794 CCD camera

Notes:
  1) 3800 - 390000 SA mode; 2750 - 1500 M ; 1500 - 25 LM;
  2) G      means calibrated with gold rings(0.236nm,0.204nm,0.144nm)
  3) GS     means using higher magnification gold ring calibrated
            image's distance between two seperated small gold particles
            along the diagonal(about 1200pixel) as a SCALE.
  4) G-CALC. calculated results from 390KX gold calibrated result with
            fomula:
             G-CALC = (390000*0.46)/current_magnifcication
  5) LHC    LHC lattice calibrated (a=12.95nm; a*=1/112.15029A-1/)
  6) LHCS   means using higher magnification LHC lattice calibrated
            image's distance between two seperated small features
            along the diagonal(about 1200pixel) as a scale.
  7) GR     calibrated with Diffraction Grating Replica
            Cat#203(2160lines/mm).
  8) GRS    means using higher magnification GR calibrated.
            mage's distance between two seperated small gold particles
            long the diagonal(about 1200pixel) as a scale.
  9) Si     Calibrated with Si(111) lattice (d=0.3135428nm).
  10) C3     different GS or L calibrated results
  11) ROT    rotating angle from CCD's Y-Axis to tilt_axis(degree) for
            different magnification(clockwise postive).
  12) SCALE  measured the distances between two fiducial marks along the
            diagonal for adjacent Magnifications,then calculates the SCALE:
            SCALE = D_Hi_Mag/D_Lo_Mag
            e.g.: D_Mag_6600 = 1374.64 pixel, D_Mag_5000 = 1033.44 pixel,
                  SCALE = 1374.64/1033.44 = 1.330 (close to 6600/5000=1.32).
  13)FINAL   final calibration results(balanced for different calibrating
            samples and for different magnifications).
LHC results indicate shrinkage of LHC lattice in negative stain between 0.5 and 5%

Calibration by Bill Rice (10/99)
used LHC crystals assuming 129.5 A lattice
pictures on film - optical diffraction using 14.5 mm reciprocal spacing for 0.1 mm real spacing
50,000 -> 52,100

First Calibration by Peijun Zhang (~1997)

* (not sure why these were modified)
Calibrated under the following conditions:
(1) Au (111) ring [2.35 Å d-spacing] was used (also LHC crystals)
(2) CCD pixel size = 24.8 micron. {[mag on CCD] / [mag on CM200]} = 1.4.
(3) Optical diffraction was used for film calibration, a 14.5mm distance on diffraction pattern corresponds a 0.1mm spacing.

Dividing Mccd/Mfilm  will give mag factor of CCD camera relative to film
for 17.5k - 100k, average is 1.319 SD=0.017
for 275k - 660k,  average is 1.264 SD=0.017
Don't know why there is a discrepancy.  Maybe higher defocus + beam convergence for lower mags