Blank-looking fields are not yet confirmed empty controls. The owner suspects focus loss partway through this round. The figures below show acquisition-order context and measurements, not automatic focus diagnoses.
Brightness changes can reflect illumination, sample, acquisition or focus effects; stage z is not biological focus quality. Recorded time text and frame-relative timestamps are retained in the audit CSV. Sequence order is used for the figure because absolute timing conventions have not yet been reconciled.
Each image is independently contrast-scaled and downsampled for screening. Sharp camera artifacts do not establish that bacteria are in focus. Inspect original slices and biological features before classifying an interval as focus failure, true empty, or unresolved.
The eight formerly selected background-only fields remain focus-unresolved. No failed-focus field is counted as zero cells or used as a confirmed empty control. A return to recognizable biological focus in adjacent acquisitions is supporting context, not proof of emptiness in the intervening field.