diff --git a/openflexure_microscope/api/default_extensions/picamera_autocalibrate/extension.py b/openflexure_microscope/api/default_extensions/picamera_autocalibrate/extension.py
index e8dc726e..5f0d9c7e 100644
--- a/openflexure_microscope/api/default_extensions/picamera_autocalibrate/extension.py
+++ b/openflexure_microscope/api/default_extensions/picamera_autocalibrate/extension.py
@@ -205,7 +205,7 @@ class AutoExposureFromRawView(ActionView):
     }
 
     def post(self, args):
-        with find_picamera() as (picamera, scamera, microscope):
+        with find_picamera() as (picamera, _, _):
             adjust_shutter_and_gain_from_raw(picamera, **args)
 
 
@@ -224,7 +224,7 @@ class AutoWhiteBalanceFromRawView(ActionView):
     }
 
     def post(self, args):
-        with find_picamera() as (picamera, scamera, microscope):
+        with find_picamera() as (picamera, _, _):
             adjust_white_balance_from_raw(picamera, **args)
 
 
@@ -238,5 +238,5 @@ class GetRawChannelPercentilesView(ActionView):
     schema = fields.List(fields.Integer)
 
     def post(self, args):
-        with find_picamera() as (picamera, scamera, microscope):
+        with find_picamera() as (picamera, _, _):
             return get_channel_percentiles(picamera, args["percentile"])
diff --git a/openflexure_microscope/api/default_extensions/picamera_autocalibrate/recalibrate_utils.py b/openflexure_microscope/api/default_extensions/picamera_autocalibrate/recalibrate_utils.py
index e6c6b5fe..352d2354 100644
--- a/openflexure_microscope/api/default_extensions/picamera_autocalibrate/recalibrate_utils.py
+++ b/openflexure_microscope/api/default_extensions/picamera_autocalibrate/recalibrate_utils.py
@@ -1,6 +1,5 @@
 import logging
 import time
-from fractions import Fraction
 from typing import List, Optional, Tuple
 
 import numpy as np
@@ -40,7 +39,7 @@ def flat_lens_shading_table(camera: PiCamera) -> np.ndarray:
 
 def adjust_exposure_to_setpoint(camera: PiCamera, setpoint: int):
     """Adjust the camera's exposure time until the maximum pixel value is <setpoint>."""
-    logging.info("Adjusting shutter speed to hit setpoint {}".format(setpoint))
+    logging.info(f"Adjusting shutter speed to hit setpoint {setpoint}")
     for _ in range(3):
         camera.shutter_speed = int(
             camera.shutter_speed * setpoint / np.max(rgb_image(camera))