Phase plate CTF Estimation » History » Version 1
Anchi Cheng, 03/05/2017 10:26 AM
| 1 | 1 | Anchi Cheng | h1. Phase plate CTF Estimation |
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| 3 | Low defocus CTF estimation can be done with CTFFind4 and gCTF. With a few critical changes of the default parameters: |
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| 5 | h2. Nominal Defocus |
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| 7 | Set this to be slightly higher than the defocus used, otherwise the algorithm tend to fit it with lower defocus values and high phase shift. |
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| 8 | !ppNominalDefocus.png! |
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| 10 | h2. Defocus Search Range |
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| 12 | Set the step of search range smaller so that it does not extend to very low defocus for the same reason above. |
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| 13 | !ppSearchRange.png! |
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| 15 | h2. Lowest Resolution for Search |
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| 17 | Because of the much higher contrast from specimen structural factor at low resolution, CTF estimation programs tend to bias phase shift estimation at this edge. |
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| 18 | Enter a value at higher resolution than any of these. See the above screenshot as an example. |
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| 20 | h2. Activate phase shift estimation |
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| 22 | Activate "Do phase shift" |
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| 23 | !ppDoPhaseShift.png! |
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| 25 | h2. Phase Shift Intial Search Range |
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| 27 | If the maximal phase shift is known, this value should be adjusted. |