typo

lib/imaging.py

@@ -145,7 +145,7 @@ class AbsorptionData(ImagingData):
 
 def compute_od(shadow: np.ndarray, bright: np.ndarray, dark: np.ndarray):
     with np.errstate(divide="ignore", invalid="ignore"):
-        T = (sh - da) / (br - da)
+        T = (shadow - dark) / (bright - dark)
         H, W = T.shape
         OD = -np.log(T)
     OD[~np.isfinite(OD)] = 0.0