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:

exposureExposure

The background-subtracted exposure containing a variance plane to be corrected for source contributions.

gainfloat, optional

The gain value for the entire image. This parameter is used if gains is not provided. If both gain and gains are None, and average_across_amps is True, gain is estimated from the image

and 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 both gain and gains are None, and average_across_amps is False, gains are estimated from the image and variance planes.

average_across_ampsbool, 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 or gains is specified.

in_placebool, 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.

Returns:

variance_planeImage

The corrected variance plane, with the signal contribution removed.

Raises:

AttributeError

If amplifiers cannot be retrieved from the exposure.

ValueError

If both gain and gains are provided, or if the number of provided gains does not match the number of amplifiers.