# Job: Downsample Particles

## **Description**

Downsample particles and save them with smaller box sizes and optionally apply filters.

![Downsample particles outputs depicting original and processed particles](https://1916621962-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M7DGv3GkRvGGpbVPCgg%2Fuploads%2F6hHVi1P24Qxc3JDsYe1A%2F33_downsample_particles_log.png?alt=media\&token=30dd0b7b-10cc-4c79-b72a-cedece9f9dc7)

## **Input**

* Particles (`blob` required; `alignments2D` and `alignments3D` optional)

## **Common Parameters**

* `Crop / pad to box size (pix)`: Crop in real space to this size before downsampling. If this number is larger than the input size, each particle will be padded with its mean pixel value
* `Desired approx. pixel size (A)`: If set, the output particles will be downsampled to have approximately the specified pixel size. Only this parameter *or* `Fourier crop to box size (pix)` should be set, not both. 
* `Fourier crop to box size (pix)`: If set, the output particles will be downsampled to have the specified number of pixels in each dimension. Only this parameter *or* `Desired approx. pixel size (A)` should be set, not both. 
* `Lowpass resolution (A)`: Resolution of corner frequency in Angstroms
* `Recenter using aligned shifts`: Activate this parameter to recenter the particles based on their shifts. 
  * Particles will only be recentered if this is true, and `alignments3D` or `alignments2D` are connected. 
  * Note that `alignments2D` will be used for recentering only if `alignments3D` are unavailable. 
  * [job-volume-alignment-tools](https://guide.cryosparc.com/processing-data/all-job-types-in-cryosparc/utilities/job-volume-alignment-tools "mention") may be used to change the geometric center of a particle stack prior to downsampling and recentering, for the purpose of subparticle cropping.
* `Save results in 16-bit floating point:` Saves the output particles in [float16 format](https://guide.cryosparc.com/processing-data/tutorials-and-case-studies/tutorial-float16-support) (CryoSPARC v4.4+).

## **Output**

* Downsampled Particles

## Common Next Steps

* Running *2D Classification, 3D Classification, 3D Variability Analysis or Heterogeneous Refinement* on downsampled particles. To refine a structure using the full particle resolution, you can reference the original (non-downsampled) particle data using an [input-group override as described in this tutorial](https://guide.cryosparc.com/processing-data/tutorials-and-case-studies/job-builder-tutorial#use-case-downsampled-particles).