normflat -- Create a flat field by normalizing a calibration image
normflat image flatfield
- Calibration image to be used.
- Flat field to be created.
- norm = INDEF
- Normalization factor to be used if not INDEF. If INDEF the normalization factor is automatically determined.
- minflat = INDEF
- Minimum data value to be used in determining the normalization and in creating the flat field. Values less than or equal to this value are replaced with a flat field value of 1.
- sample_section = ""
- Section of the image to be sampled in determining the normalization if norm = INDEF.
A flat field is created from a calibration image by normalizing the calibration image. The normalization is specified with the parameter norm . If the value of norm is INDEF then the normalization is determined by sampling the pixels in the sample section with values greater than minflat . This task differs from the task normalize in that data values less than or equal to minflat are replaced with unity in the normalized flat field.
To create a flat field from a calibration image "quartz" using pixels above 1000 and selecting the normalization to be 3500:
cl> normflat quartz flat norm=3500 minflat=1000
To determine a normalization from the pixels above 1000 and sampling every fifth pixel in each dimension:
cl> normflat quartz flat minflat=1000 sample=[*:5,*:5]