diff --git a/python/lsst/cp/pipe/ptc/cpPtcExtract.py b/python/lsst/cp/pipe/ptc/cpPtcExtract.py
index 4b800390..4839ee65 100644
--- a/python/lsst/cp/pipe/ptc/cpPtcExtract.py
+++ b/python/lsst/cp/pipe/ptc/cpPtcExtract.py
@@ -30,7 +30,7 @@
 from lsst.geom import (Box2I, Point2I, Extent2I)
 from lsst.cp.pipe.utils import (arrangeFlatsByExpTime, arrangeFlatsByExpId,
                                 arrangeFlatsByExpFlux, sigmaClipCorrection,
-                                CovFastFourierTransform)
+                                CovFastFourierTransform, getReadNoise)
 
 import lsst.pipe.base.connectionTypes as cT
 
@@ -66,6 +66,7 @@ class PhotonTransferCurveExtractConnections(pipeBase.PipelineTaskConnections,
         storageClass="TaskMetadata",
         dimensions=("instrument", "exposure", "detector"),
         multiple=True,
+        deprecated="This connection is deprecated and will be removed after v28.",
     )
     outputCovariances = cT.Output(
         name="ptcCovariances",
@@ -515,16 +516,14 @@ def run(self, inputExp, inputDims, taskMetadata, inputPhotodiodeData=None):
                 readNoise2 = dict()
                 meanReadNoise = dict()
 
-                expMetadata1 = expRef1.get(component="metadata")
                 metadataIndex1 = inputDims.index(expId1)
                 thisTaskMetadata1 = taskMetadata[metadataIndex1]
 
-                expMetadata2 = expRef2.get(component="metadata")
                 metadataIndex2 = inputDims.index(expId2)
                 thisTaskMetadata2 = taskMetadata[metadataIndex2]
 
-                readNoise1[ampName] = self.getReadNoise(expMetadata1, thisTaskMetadata1, ampName)
-                readNoise2[ampName] = self.getReadNoise(expMetadata2, thisTaskMetadata2, ampName)
+                readNoise1[ampName] = getReadNoise(exp1, ampName, taskMetadata=thisTaskMetadata1)
+                readNoise2[ampName] = getReadNoise(exp2, ampName, taskMetadata=thisTaskMetadata2)
 
                 meanReadNoise[ampName] = np.nanmean([readNoise1[ampName], readNoise2[ampName]])
 
@@ -1042,43 +1041,6 @@ def getGainFromFlatPair(self, im1Area, im2Area, imStatsCtrl, mu1, mu2,
 
         return gain
 
-    def getReadNoise(self, exposureMetadata, taskMetadata, ampName):
-        """Gets readout noise for an amp from ISR metadata.
-
-        If possible, this attempts to get the now-standard headers
-        added to the exposure itself.  If not found there, the ISR
-        TaskMetadata is searched.  If neither of these has the value,
-        warn and set the read noise to NaN.
-
-        Parameters
-        ----------
-        exposureMetadata : `lsst.daf.base.PropertySet`
-            Metadata to check for read noise first.
-        taskMetadata : `lsst.pipe.base.TaskMetadata`
-            List of exposures metadata from ISR for this exposure.
-        ampName : `str`
-            Amplifier name.
-
-        Returns
-        -------
-        readNoise : `float`
-            The read noise for this set of exposure/amplifier.
-        """
-        # Try from the exposure first.
-        expectedKey = f"LSST ISR OVERSCAN RESIDUAL SERIAL STDEV {ampName}"
-        if expectedKey in exposureMetadata:
-            return exposureMetadata[expectedKey]
-
-        # If not, try getting it from the task metadata.
-        expectedKey = f"RESIDUAL STDEV {ampName}"
-        if "isr" in taskMetadata:
-            if expectedKey in taskMetadata["isr"]:
-                return taskMetadata["isr"][expectedKey]
-
-        self.log.warning("Median readout noise from ISR metadata for amp %s "
-                         "could not be calculated." % ampName)
-        return np.nan
-
     def computeGaussianHistogramParameters(self, im1Area, im2Area, imStatsCtrl, mu1, mu2):
         """Compute KS test for a Gaussian model fit to a histogram of the
         difference image.
diff --git a/python/lsst/cp/pipe/utils.py b/python/lsst/cp/pipe/utils.py
index 02701e47..3d61b372 100644
--- a/python/lsst/cp/pipe/utils.py
+++ b/python/lsst/cp/pipe/utils.py
@@ -20,7 +20,7 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #
 
-__all__ = ['ddict2dict', 'CovFastFourierTransform']
+__all__ = ['ddict2dict', 'CovFastFourierTransform', 'getReadNoise']
 
 
 import galsim
@@ -1311,3 +1311,47 @@ def __call__(self, pars):
             constraint = np.hstack([constraint, log_w])
 
         return np.hstack([resid, constraint])
+
+
+def getReadNoise(exposure, ampName, taskMetadata=None, log=None):
+    """Gets readout noise for an amp from ISR metadata.
+
+    If possible, this attempts to get the now-standard headers
+    added to the exposure itself.  If not found there, the ISR
+    TaskMetadata is searched.  If neither of these has the value,
+    warn and set the read noise to NaN.
+
+    Parameters
+    ----------
+    exposure : `lsst.afw.image.Exposure`
+        Exposure to check for read noise first.
+    ampName : `str`
+        Amplifier name.
+    taskMetadata : `lsst.pipe.base.TaskMetadata`, optional
+        List of exposures metadata from ISR for this exposure.
+    log : `logging.logger`, optional
+        Log for messages.
+
+    Returns
+    -------
+    readNoise : `float`
+        The read noise for this set of exposure/amplifier.
+    """
+    exposureMetadata = exposure.getMetadata()
+
+    # Try from the exposure first.
+    expectedKey = f"LSST ISR OVERSCAN RESIDUAL SERIAL STDEV {ampName}"
+    if expectedKey in exposureMetadata:
+        return exposureMetadata[expectedKey]
+
+    # If not, try getting it from the task metadata.
+    if taskMetadata:
+        expectedKey = f"RESIDUAL STDEV {ampName}"
+        if "isr" in taskMetadata:
+            if expectedKey in taskMetadata["isr"]:
+                return taskMetadata["isr"][expectedKey]
+
+    log = log if log else logging.getLogger(__name__)
+    log.warning("Median readout noise from ISR metadata for amp %s "
+                "could not be found." % ampName)
+    return np.nan