diff --git a/routes/acquisition.py b/routes/acquisition.py
index 8896f0c..029d065 100644
--- a/routes/acquisition.py
+++ b/routes/acquisition.py
@@ -48,9 +48,8 @@ def run(object_id: int):
 
     def generate():
         yield str(acquisition.id)
-        length = len(config.LEDS_UUIDS) + 2  # with all_on and all_off
-        for index, led_uuid in enumerate(scanner.scan(join(config.OBJECT_DIR, str(object.id), str(acquisition.id)))):
-            yield f"{led_uuid},{(index+1)/length}\n"
+        for value in scanner.scan(join(config.OBJECT_DIR, str(object.id), str(acquisition.id))):
+            yield value
 
     return Response(generate(), mimetype='text/plain')
 
@@ -74,9 +73,8 @@ def rescan(acquisition_id: int):
     object = acquisition.object(conn)
 
     def generate():
-        length = len(config.LEDS_UUIDS) + 2  # with all_on and all_off
-        for index, led_uuid in enumerate(scanner.scan(join(config.OBJECT_DIR, str(object.id), str(acquisition.id)))):
-            yield f"{led_uuid},{(index+1)/length}\n"
+        for value in scanner.scan(join(config.OBJECT_DIR, str(object.id), str(acquisition.id))):
+            yield value
 
     return Response(generate(), mimetype='text/plain')
 
diff --git a/routes/calibration.py b/routes/calibration.py
index 5c817c4..35b56ec 100644
--- a/routes/calibration.py
+++ b/routes/calibration.py
@@ -56,9 +56,8 @@ def scan():
         calibration = utils.get_calibration(conn)
 
     def generate():
-        length = len(config.LEDS_UUIDS)
-        for index, led_uuid in enumerate(scanner.scan(join(config.CALIBRATION_DIR, calibration_id), False)):
-            yield f"{led_uuid},{(index+1)/length}\n"
+        for value in scanner.scan(join(config.CALIBRATION_DIR, calibration_id), False):
+            yield value
 
         with conn:
             calibration.state = db.CalibrationState.HasData
diff --git a/scanner.py b/scanner.py
index b221deb..9cc87cf 100644
--- a/scanner.py
+++ b/scanner.py
@@ -35,6 +35,8 @@ def scan(output_dir: str, on_and_off: bool = True):
     os.makedirs(output_dir, exist_ok=True)
 
     file_paths = []
+    length = len(config.LEDS_UUIDS) + (2 if on_and_off else 0)
+
     with camera.get() as cam:
         with leds.get() as gpio_leds:
             for count, led in enumerate(gpio_leds.leds):
@@ -46,15 +48,23 @@ def scan(output_dir: str, on_and_off: bool = True):
 
                 print(f'Turn off {led}')
 
+                ratio = (count + 1) / (2 * length)
+                yield f'{{ "status": "captured", "id": "{led}", "ratio": {ratio:.3} }}\n'
+
             # capture with all leds ON OFF
             if on_and_off:
                 gpio_leds.on()
                 file_paths.append(('all_on', delay_capture(cam)))
+                ratio = (length - 1) / (2 * length)
+                yield f'{{ "status": "captured", "id": "all_on", "ratio": {ratio:.3} }}\n'
 
                 gpio_leds.off()
                 file_paths.append(('all_off', delay_capture(cam)))
+                ratio = 0.5
+                yield f'{{ "status": "captured", "id": "all_off", "ratio": {ratio:.3} }}\n'
 
     with camera.get() as cam:
-        for target, source in file_paths:
+        for count, (target, source) in enumerate(file_paths):
             delay_save(cam, source, join(output_dir, target))
-            yield target
+            ratio = 0.5 + (count + 1) / (2 * length)
+            yield f'{{ "status": "ready", "id": "{target}", "ratio": {ratio:.3} }}\n'
diff --git a/templates/calibrate.html b/templates/calibrate.html
index cefc74e..b8cf3b5 100644
--- a/templates/calibrate.html
+++ b/templates/calibrate.html
@@ -86,15 +86,20 @@
                 break;
             }
 
-            let [ uuid, ratio ] = value.trim().split(',');
+            console.log(value);
+            let { status, id, ratio } = JSON.parse(value);
+            console.log(status, id, ratio);
             progress = Math.ceil(1000 * parseFloat(ratio));
-            let cell = document.createElement('div');
-            cell.classList.add('cell');
-            let img = document.createElement('img');
-            img.classList.add('is-loading');
-            img.src = '/data/calibrations/{{ calibration.id }}/' + uuid + '.jpg?v=' + scanIndex;
-            cell.appendChild(img);
-            grid.appendChild(cell);
+
+            if (status === "ready") {
+                let cell = document.createElement('div');
+                cell.classList.add('cell');
+                let img = document.createElement('img');
+                img.classList.add('is-loading');
+                img.src = '/data/calibrations/{{ calibration.id }}/' + id + '.jpg?v=' + scanIndex;
+                cell.appendChild(img);
+                grid.appendChild(cell);
+            }
         }
     });
 
diff --git a/templates/scan.html b/templates/scan.html
index 27d70ea..706af5c 100644
--- a/templates/scan.html
+++ b/templates/scan.html
@@ -156,15 +156,18 @@
                 continue;
             }
 
-            let [ uuid, ratio ] = value.trim().split(',');
+            let { status, id, ratio } = JSON.parse(value);
             progress = Math.ceil(1000 * parseFloat(ratio));
-            let cell = document.createElement('div');
-            cell.classList.add('cell');
-            let img = document.createElement('img');
-            img.classList.add('is-loading');
-            img.src = '/data/objects/{{ object.id }}/' + acquisitionId + '/' + uuid + '.jpg?v=' + scanIndex;
-            cell.appendChild(img);
-            grid.appendChild(cell);
+
+            if (status === "ready") {
+                let cell = document.createElement('div');
+                cell.classList.add('cell');
+                let img = document.createElement('img');
+                img.classList.add('is-loading');
+                img.src = '/data/objects/{{ object.id }}/' + acquisitionId + '/' + id + '.jpg?v=' + scanIndex;
+                cell.appendChild(img);
+                grid.appendChild(cell);
+            }
         }
     });