2 Packing and Compression

To take the advantage of the integer pixel values of Counted and Super-res image, one way that SerialEM uses is to "pack" the data. Specifically, for Counted image, the pixel values are truncated into byte from 16-bit integer before saving. And for Super-res image, the two 4-bit data is packed into one 1-byte space. It reduces the file size to half of the original, in both cases.

Another way SerialEM uses to save file size is to use compression. Currently, two kind of compression methods are used, they are LZW and ZIP. Both are lossless methods. Compression is only available for TIFF images. And it can be used on top of packed data too. In another word, one can select to have a stack saved as packed and also compressed, for TIFF format. For MRC type selected, only packing is available. However, MRC image should also be able to be compressed. This can only be done manually as a separate post-process.

Below is the Camera Parameter Setup window. Pay attention to the right lower corner of the window where one can define how to save K2 frame files by clicking on "Set File Option" button.

Clicking on "Set File Option" brings up a dialog window "K2 Frame File Options" as below.

As you can see, you can also choose not to rotate/flip frames.