implementing reviewer comments

docs/changes/2636.feature.rst

@@ -1,3 +1,4 @@
 Update ``CameraCalibrator`` in ``ctapipe.calib.camera.calibrator`` allowing it to correctly calibrate variance images generated with the ``VarianceExtractor``.
-  - If the VarianceExtractor is used for the ``CameraCalibrator`` the element-wise square of the relative and absolute gain calibration factors are applied to the image;
+  - If the ``VarianceExtractor`` is used for the ``CameraCalibrator`` the element-wise square of the relative and absolute gain calibration factors are applied to the image;
   - For other image extractors the plain factors are still applied.
+  - The ``VarianceExtractor`` provides no peak time and the calibrator will not try to skip shifting the peak time for extractors like the ``VarianceExtractor`` that similarly do not provide a peak time

src/ctapipe/calib/camera/calibrator.py

@@ -284,9 +284,9 @@ def _calibrate_dl1(self, event, tel_id):
 
             # correct non-integer remainder of the shift if given
             if (
-                self.apply_peak_time_shift.tel[tel_id]
+                dl1.peak_time is not None
+                and self.apply_peak_time_shift.tel[tel_id]
                 and remaining_shift is not None
-                and dl1.peak_time is not None
             ):
                 dl1.peak_time -= remaining_shift
 

src/ctapipe/calib/camera/tests/test_calibrator.py

@@ -137,14 +137,14 @@ def test_dl1_variance_calib(example_subarray):
         image_extractor=VarianceExtractor(subarray=example_subarray),
         apply_waveform_time_shift=False,
     )
-    n_channels = 2
     n_samples = 100
 
     event = ArrayEventContainer()
 
     for tel_type in example_subarray.telescope_types:
         tel_id = example_subarray.get_tel_ids_for_type(tel_type)[0]
         n_pixels = example_subarray.tel[tel_id].camera.geometry.n_pixels
+        n_channels = example_subarray.tel[tel_id].camera.readout.n_channels
 
         random = np.random.default_rng(1)
         y = random.normal(0, 6, (n_channels, n_pixels, n_samples))
@@ -170,9 +170,10 @@ def test_dl1_variance_calib(example_subarray):
     for tel_type in example_subarray.telescope_types:
         tel_id = example_subarray.get_tel_ids_for_type(tel_type)[0]
         image = event.dl1.tel[tel_id].image
+        camera = example_subarray.tel[tel_id].camera
         assert image is not None
         assert image.shape == (
-            2,
+            camera.readout.n_channels,
             example_subarray.tel[tel_id].camera.geometry.n_pixels,
         )