diff --git a/tests/lens_tests/test_canon_lenses.py b/tests/lens_tests/test_canon_lenses.py
index 3217574d..37f5200a 100644
--- a/tests/lens_tests/test_canon_lenses.py
+++ b/tests/lens_tests/test_canon_lenses.py
@@ -4,7 +4,7 @@ import re
 import os
 import system_tests
 import math
-from lens_tests.utils import extract_lenses_from_cpp
+from lens_tests.utils import extract_lenses_from_cpp, make_test_cases
 
 # get directory of the current file
 file_dir = os.path.dirname(os.path.realpath(__file__))
@@ -14,38 +14,37 @@ canon_lens_file = os.path.abspath(os.path.join(file_dir, "./../../src/canonmn_in
 startpattern = "constexpr TagDetails canonCsLensType[] = {"
 # use utils function to extract all lenses
 lenses = extract_lenses_from_cpp(canon_lens_file, startpattern)
+# use utils function to define test case data
+test_cases = make_test_cases(lenses)
 
+# see https://github.com/exiftool/exiftool/blob/master/lib/Image/ExifTool/Canon.pm#L9678
 def aperture_to_raw_exif(aperture):
-    #see https://github.com/exiftool/exiftool/blob/master/lib/Image/ExifTool/Canon.pm#L9678
-    aperture = float(aperture)
     # for apertures < 1 the below is negative
-    num = math.log(aperture)*2/math.log(2)
+    num = math.log(aperture) * 2 / math.log(2)
 
     # temporarily make the number positive
-    if (num < 0):
+    if num < 0:
         num = -num
         sign = -1
     else:
-        sign = 1;
+        sign = 1
 
     val = int(num)
     frac = num - val
 
-    if (abs(frac - 0.33) < 0.05):
-        frac = 0x0c
-    elif (abs(frac - 0.67) < 0.05):
-        frac = 0x14;
+    if abs(frac - 0.33) < 0.05:
+        frac = 0x0C
+    elif abs(frac - 0.67) < 0.05:
+        frac = 0x14
     else:
         frac = int(frac * 0x20 + 0.5)
 
-    return sign * (val * 0x20 + frac);
+    return sign * (val * 0x20 + frac)
 
 
-for (lens_id, lens_desc, meta) in lenses:
+for lens_tc in test_cases:
 
-    tc = float(meta["tc"] or 1)
-
-    testname = lens_id + "_" + lens_desc
+    testname = lens_tc["id"] + "_" + lens_tc["desc"]
 
     globals()[testname] = system_tests.CaseMeta(
         "canon_lenses." + testname,
@@ -58,10 +57,10 @@ for (lens_id, lens_desc, meta) in lenses:
             "stderr": [""],
             "stdout": ["Exif.CanonCs.LensType                        Short       1  $lens_description\n"],
             "retval": [0],
-            "lens_id": lens_id,
-            "lens_description": lens_desc,
-            "aperture_max": aperture_to_raw_exif(meta["aperture_max_short"]),
-            "focal_length_min": int(int(meta["focal_length_min"]) * tc),
-            "focal_length_max": int(int(meta["focal_length_max"]) * tc),
+            "lens_id": lens_tc["id"],
+            "lens_description": lens_tc["target"],
+            "aperture_max": aperture_to_raw_exif(lens_tc["aperture_max_short"]),
+            "focal_length_min": int(lens_tc["focal_length_min"] * lens_tc["tc"]),
+            "focal_length_max": int(lens_tc["focal_length_max"] * lens_tc["tc"]),
         },
     )
diff --git a/tests/lens_tests/utils.py b/tests/lens_tests/utils.py
index 31e7afa6..fa03cf86 100644
--- a/tests/lens_tests/utils.py
+++ b/tests/lens_tests/utils.py
@@ -1,6 +1,7 @@
 import re
 import os
 import logging
+from itertools import groupby
 
 log = logging.getLogger(__name__)
 
@@ -49,17 +50,54 @@ def extract_meta(text, pattern=LENS_META_DEFAULT_RE):
     """
     result = pattern.match(text)
 
-    if(not result):
+    if not result:
         # didn't match
         return None
 
     ret = result.groupdict()
     # set min to max value if we didn't get a range but a single value
-    ret['focal_length_min'] = ret['focal_length_min'] or ret['focal_length_max']
-    ret['aperture_max_short'] = ret['aperture_max_short'] or ret['aperture_max_tele']
+    ret["focal_length_min"] = int(ret["focal_length_min"] or ret["focal_length_max"])
+    ret["focal_length_max"] = int(ret["focal_length_max"])
+    ret["aperture_max_short"] = float(ret["aperture_max_short"] or ret["aperture_max_tele"])
+    ret["aperture_max_tele"] = float(ret["aperture_max_tele"])
+    ret["tc"] = float(ret["tc"] or 1)
     return ret
 
 
+# FIXME explain somwhere that lens_is_match(l1,l2) does not imply lens_is_match(l2,l1)
+# becuse we don't have short and tele aperture values in exif
+def lens_is_match(l1, l2):
+    """
+    Test if lens l2 is compatible with lens l1,
+    assuming we write l1's metadata and apeture_max_short into exif
+    """
+    return (
+        all([l1[k] == l2[k] for k in ["tc", "focal_length_min", "focal_length_max"]])
+        and l2["aperture_max_short"] <= l1["aperture_max_short"] <= l2["aperture_max_tele"]
+    )
+
+
+def make_test_cases(lenses):
+    """
+    Creates a test case for each lens
+    Main job of this function is to collect all ambiguous lenses and define a test target
+    as the " *OR* " joined string of all ambiguous lens descriptions
+    """
+    test_cases = []
+    for lens_id, group in groupby(lenses, lambda x: x["id"]):
+        lens_group = list(group)
+        test_cases += [
+            {
+                **lens["meta"],
+                "id": lens["id"],
+                "desc": lens["desc"],
+                "target": " *OR* ".join([l["desc"] for l in lens_group if lens_is_match(lens["meta"], l["meta"])]),
+            }
+            for lens in lens_group
+        ]
+    return test_cases
+
+
 def extract_lenses_from_cpp(filename, start_pattern):
     """
     Extract lens information from the lens descritpions array in a maker note cpp file
@@ -99,6 +137,5 @@ def extract_lenses_from_cpp(filename, start_pattern):
                     log.error(f"Failure extracing metadata from lens description:  {lens_entry[0]}: {lens_entry[1]}.")
                     continue
 
-                lenses.append((*lens_entry, meta))
+                lenses.append({"id": lens_entry[0], "desc": lens_entry[1], "meta": meta})
         return lenses
-