diff --git a/xgm.py b/xgm.py
index 86415110902eda26b7cb166115057908bc8f43f1..b4a3c6473f600a0fa6085712caea530991aa50ed 100644
--- a/xgm.py
+++ b/xgm.py
@@ -591,7 +591,7 @@ tim_calibration_table = {
         [ 3.69445588e-11, -1.97731342e-07,  3.98203522e-04, -3.78338599e-01,  1.41894119e+02]])
 }
 
-def timFactorFromVoltage(voltage, photonEnergy=None, mcp=1):
+def timFactorFromTable(voltage, photonEnergy, mcp=1):
     ''' Returns an energy calibration factor for TIM integrated peak signal (APD)
         according to calibration from March 2019, proposal 900074, semester 201930, 
         runs 69 - 111 (Ni edge):  https://in.xfel.eu/elog/SCS+Beamline/2323
@@ -603,15 +603,12 @@ def timFactorFromVoltage(voltage, photonEnergy=None, mcp=1):
             voltage: MCP voltage in volts.
             photonEnergy: FEL photon energy in eV. Calibration factor is linearly
                 interpolated between the known values from the calibration table. 
-                If None, takes the median photon energy from the calibration table.
             mcp: MCP channel (1, 2, or 3).
             
         Output:
             f: calibration factor in microjoule per APD signal
     '''
     energies = np.sort([key for key in tim_calibration_table])
-    if photonEnergy is None:
-        photonEnergy = np.median(energies)
     if photonEnergy not in photon_energies:
         if photonEnergy > energies.max():
             photonEnergy = energies.max()
@@ -628,4 +625,3 @@ def timFactorFromVoltage(voltage, photonEnergy=None, mcp=1):
     poly = np.poly1d(tim_calibration_table[photonEnergy][mcp-1])
     f = -np.exp(poly(voltage))
     return f
-    
\ No newline at end of file