# Job: Validation (FSC)

## Description

This job runs FSC calculation using input half-maps. It can either use a provided mask, or generate a new mask by thresholding, dilating, and soft-padding of the input density. It can also optionally re-optimize the tightness of the FSC mask. It also outputs FSC plots in `.txt` and `.xml` format for EMDB compatibility. [Read more here.](https://guide.cryosparc.com/processing-data/all-job-types-in-cryosparc/post-processing/broken-reference)

In CryoSPARC v3.3+, this job can now run GPU calculation and mask generation on the GPU for a substantial speedup.

## Inputs

* a volume group containing two half-maps
* an optional mask input containing a mask to use for FSC calculation

## Outputs

* the final mask that was used (in case the mask was optimized or generated within the job)

## Common Parameters

* `Generate new FSC mask` instructs the job to create a new mask using the below parameters
* `Use Relative Threshold` instructs the job to interpret the threshold provided as a fraction of the maximum density in the volume (so the value should be between zero and one). If this is turned off, the threshold is interpreted as an absolute value.
* `mask near (A)` is the distance to dilate the mask in Angstroms
* `mask far (A)` is the distance to softly pad the mask after dilation. The final mask contains ones until the near distance, and falls of to zero at the far distance.
* `Optimize FSC mask` tells the job to run FSC mask auto-tightening to make sure the mask is as tight as possible without biasing the FSC curve
* `Override pixel size (A)` tells the job to use a different pixel size than the pixel size recorded in the input half-maps. If there is a small error (a few percent) in the original pixel size used during processing, a new pixel size can be input here to override the old pixel size. This will scale the FSC plots correctly, and output the half-maps with the corrected pixel size.