remove_signal_from_variance¶
- lsst.meas.algorithms.remove_signal_from_variance(exposure, gain=None, gains=None, average_across_amps=False, in_place=False)¶
Removes the Poisson contribution from actual sources in the variance plane of an Exposure.
If neither gain nor gains are provided, the function estimates the gain(s). If
average_across_amps
is True, a single gain value for the entire image is estimated. If False, individual gain values for each amplifier are estimated. The estimation involves a linear fit of variance versus image plane.- Parameters:
- exposure
Exposure
The background-subtracted exposure containing a variance plane to be corrected for source contributions.
- gain
float
, optional The gain value for the entire image. This parameter is used if
gains
is not provided. If bothgain
andgains
are None, andaverage_across_amps
is True,gain
is estimated from the imageand variance planes.
- gainsdict[
str
,float
], optional A dictionary mapping amplifier ID (as a string) to gain value. This parameter is used if
gain
is not provided. If bothgain
andgains
are None, andaverage_across_amps
is False,gains
are estimated from the image and variance planes.- average_across_amps
bool
, optional Determines the gain estimation strategy. If True, the gain for the entire image is estimated at once. If False, individual gains for each amplifier are estimated. This parameter is ignored if either
gain
orgains
is specified.- in_place
bool
, optional If True, the variance plane of the input Exposure is modified in place. A modified copy of the variance plane is always returned irrespective of this.
- exposure
- Returns:
- variance_plane
Image
The corrected variance plane, with the signal contribution removed.
- variance_plane
- Raises:
- AttributeError
If amplifiers cannot be retrieved from the exposure.
- ValueError
If both
gain
andgains
are provided, or if the number of providedgains
does not match the number of amplifiers.