EXPERIMENTAL DETECTION / FISH.MOV

Ten frames, counted

Background subtraction sampled the video every 200 ms. These ten frames span the clip. This tank contains five fish. Each card compares its detected dark blobs with that known count.

Detected regionExported center position

Tank at 0 seconds with 5 detected blobs outlined in red

0 seconds5 detected

Matches known count

Tank at 5 seconds with 5 detected blobs outlined in red

5 seconds5 detected

Matches known count

Tank at 10 seconds with 6 detected blobs outlined in red

10 seconds6 detected

1 above known count

Tank at 20 seconds with 6 detected blobs outlined in red

20 seconds6 detected

1 above known count

Tank at 30 seconds with 6 detected blobs outlined in red

30 seconds6 detected

1 above known count

Tank at 50 seconds with 4 detected blobs outlined in red

50 seconds4 detected

1 below known count

Tank at 60 seconds with 5 detected blobs outlined in red

60 seconds5 detected

Matches known count

Tank at 70 seconds with 7 detected blobs outlined in red

70 seconds7 detected

2 above known count

Tank at 90 seconds with 4 detected blobs outlined in red

90 seconds4 detected

1 below known count

Tank at 110 seconds with 5 detected blobs outlined in red

110 seconds5 detected

Matches known count

Tank walls and reflections can create false detections. Fish that touch or overlap can appear as one blob. A count of five does not guarantee that all five positions are correct. The 0.5-inch paper grid measures roughly 15–16 pixels per square in the central tank area, or about 30–32 pixels per inch; perspective makes this an approximate distance scale. The page shows the tank crop; exported coordinates refer to the original video.