Where the specks come from
Three sources account for nearly all of them. Dust on the sensor, which lands in the same coordinates on every frame from that body until it is cleaned. A smear on the front of the glass, which is soft, wide and usually in one corner. Something on the subject side — a raindrop on a window, a crumb on a table, a hair on a scanner bed.
Sensor dust shows itself against a wide even field: a pale sky, a white wall, a sheet of paper. It is close to invisible against foliage, which is why it survives for months without anybody noticing.
Working through a frame
- Open the file. The spot fix is already armed on this page.
- Tap each mark once. A numbered tag lands where you tapped.
- Drag the seam across and look at the tags. What was there on the left should not be there on the right.
- If a tag is in the wrong place, click it and press Backspace, or use the Remove button on its row.
- Keep these fixes. The same records run again against the full-size pixels on the way out.
Six per photograph. If a frame genuinely has more than six marks on it, the sensor wants cleaning more than the file wants tapping.
Questions about specks
- How small is small enough?
- If the mark fits inside a circle the width of your smallest fingernail on screen at full size, it is this tool's job. If you would have to trace round it, it is not.
- There are marks in the same place on every photograph from one card.
- That is dust on the sensor or on the rear of the lens, and it lands in the same coordinates every time. Open one frame, note where the tags end up, and the rest of the card will have them in the same places.
- The mark sits on a brick wall and the fill made a mess.
- It will. A disc filled from its surroundings reproduces the surroundings, and a repeating pattern with a hard grid does not survive being averaged. The seam shows you that before you save.
- Can it find the specks for me?
- No. Finding them is a detection job and detection is what turns a small tool into a large one. You point; the tool fills.