====== Calibration – Read Calibrated Images ======
To read calibrated images from a folder that has a calibration file, check the "calibration" flag in [[basic_level:readimage_and_show|ReadImage]] or [[basic_level:readstack_multispectral_image|ReadStack]]. The read module looks up the name of each file in the calibration file, gets the mean value of the calibration target, and divides the incoming values by it, producing calibrated data on the fly.
  * If "calibration" is checked but the folder has no calibration file, the job stops. To create one, see [[advanced_level:calibration:generate_cal_file|Generate Cal File]].
  * Calibration works only with single-band image files.

===== Example: PCA on calibrated data =====
{{ :advanced_level:calibration:hoku_advanced_cal_read_1.png?nolink&800 |Two ReadStack modules with calibration checked, feeding PCA}}

The example shows a PCA computation. The dialog shows that the "input" image is on the left and the "ROI" image comes from the top. Note the small window for the region of interest, and that both ReadStack modules have "calibration" checked. Calibrating the data before analyzing it with [[basic_level:pca_principal_components_analysis|PCA]] may give a better result.