K2 acquire image » History » Revision 2
Revision 1 (Anchi Cheng, 07/11/2014 06:50 PM) → Revision 2/11 (Anchi Cheng, 07/11/2014 06:52 PM)
h1. Acquiring K2 images acquire image h2. Recommended dose rate and exposure time for different K2 modes This recommendation is based on our experience. As a general rule, the dose rate corresponds to the value used during DM gain reference acquisition. You can put down the small viewing screen once the intensity is adjusted at the beginning of DM procedure to get the values. You will notice that Linear mode calibration uses much higher beam intensity than the calibration for counted/super-resolution modes. For our Tecnai F20 at 200 kV, the former reading of exposure time by the small viewing screen is 0.25 s while the value for latter is 1.6 s. You should use similar intensity during Leginon calibration and data collection. At 1.2 A/pixel, we use the following for final exposure that has binning of 1: |mode|small viewing screen exp time (s)|detector dose rate (e/physical pixel)|acquisition exposure time for ~ 20 e/A^2 specimen dose with 1.2 A/pixel pixel size (s)| |Linear|0.25|64|0.5| |Counted/Super-resolution*|1.6|10|5.0| *Most literature recommend at even lower dose in the range of 6-8 e/s/pixel. This is just a number we have had success with. h2. Preset Recommendation See [[Pre-MSI_Set-up#Preset-Design-Example-for-small-pixel-Gatan-K2-camera-alone]] specific for K2 camera using counted/super-resolution mode.