Count test tubes in a rack from a photo

Counting test tubes from directly above the rack

Test tubes in a rack are easiest to count from overhead, where every cap or open mouth becomes a small circle in a grid. Lab managers use that photo for consumable stock counts across racks, for a sample batch tally before a run, and for goods-in checks against a supplier order. The usual trap is the rack itself: an empty rack hole is also a ring, and from above it can look a lot like an uncapped tube. Capped tubes with colored tops separate cleanly from empty positions; open tubes need a closer look at every marker.

Hold the phone level over the center of the rack so the outer rows are not seen at a slant, which makes tall tubes lean into one another in the frame. When a rack mixes cap colors or tube sizes, use Similar items and mark one example of each kind, up to three, and the Found per example rows show how the total splits. Loose tubes still in their bag should be tipped onto a tray and spread one layer deep first.

Handwriting and barcodes on the labels are not read, so sample IDs still come from your log. Add each rack as its own labelled tally row and export the CSV for the lab record. Vials standing in a rack follow the same overhead method, and a consumables stock-take across several shelves fits better on the inventory counter.

Rack checks before you shoot

• Shoot straight down, not from the front of the bench
• Fill the frame with one rack at a time
• Note empty positions in the tally label if they matter to you
• Mark a capped tube as the example when the rack also holds open ones