Why a camera can drift dirty without anyone noticing
A camera that slowly gets dirty loses contrast day by day. Fine defects disappear or false alarms rise. It is not a sudden ink blot. Read the grey on the same test sheet each day. If it leaves the agreed range, wipe the lens. Do not lower the sensitivity first.
A camera that slowly gets dirty usually loses contrast day by day. Fine defects disappear, or false alarms increase. It is not a sudden blot of ink on the picture. Each day, read the grey on the same test sheet. If it leaves the agreed range, wipe the lens. Do not lower the sensitivity first.
Why it is judged this way
An ink haze on the lens pulls black and white toward the middle. An operator who looks every day does not notice. Write the same solid and the same white patch on the test sheet as two numbers. If they walk toward each other for three days in a row, the lens is dirty. The job has not changed.
What to compare
| What you see | Call it | Do not |
|---|---|---|
| The test-sheet contrast falls for days | Wipe the lens and the lamp cover first | Lower the sensitivity |
| Only one patch turns black suddenly | Look for a job defect first | Decide it is the lens |
| After the wipe, contrast is back in the old range | The press may continue | Leave the cleaning unrecorded |
Check at a job change or a new roll
- Keep one test sheet fixed. Write the grey of the solid and the grey of the white.
- If the contrast shrinks, wipe, then measure again. Do not change the threshold first.
- Write the cleaning date on the handover board.
