What this mode does
A negative records light as density: the more light a part of the scene sent, the denser the film became. The scan, though, records how much light the film let through. This page turns one into the other. Each channel is divided by the film base, which removes the orange mask, then converted to density (the logarithm of base over pixel) and stretched between that channel’s own measured ends, so the densest part of the negative becomes the brightest part of the photograph.
The density range each channel held is shown, and a mid-tone control moves the curve. When the preview looks right, the positive opens on the bench at full size, where dust, scratches and fading are repaired as on any other scan.
When this is the wrong tool
- A scan made with the scanner's own negative mode is already inverted. Skip the conversion and repair it as a positive.
- Badly underexposed negatives have little density to work with; the positive will be noisy in the shadows, and no setting adds detail that is not on the film.
- Colour balance after conversion is a starting point. Use Tone on the bench, or the measured-neutral tools, for the final balance.
Questions about negative to positive
Why is a colour negative orange?
The film base of a colour negative carries an orange mask, built in to correct for the dyes' imperfections when printed on photographic paper. Simply inverting the scan turns that orange into a strong blue cast. This page measures the mask from clear film and divides it out of each channel before inverting, which is what removes the cast.
Where does the film base measurement come from?
From the clear film along an edge of the frame, when the scan includes some: each edge strip is tested, and an even, bright strip is taken as the base. If there is none, the clearest half per cent of the frame stands in, and the page says so. You can always click a point of clear film yourself.
Does it work on black and white negatives?
Yes. Choose Black and white and the three channels are inverted together from one measurement, so no colour is introduced. A silver negative's base is close to grey, and the page suggests this setting when the measured base has no orange in it.
Why is dust cleaned after converting?
Dust and hairs on a negative block light, so they are white on the negative scan and dark on the positive. The dust detector looks for marks against the picture as it will be seen, so it runs on the positive, once the conversion is done.
Is my negative uploaded?
No. The conversion and the repair run in this tab, and nothing is sent.
Related
- Restore an old photographOpens on fade correction, for a print that has gone pale and warm.
- Restore a faded colour photoPer-channel fade and cast correction with dye-fade starting points for prints gone orange or magenta.
- Restore black and white photosLinked-channel tone so no colour is added; a sepia or selenium print keeps its tone unless you neutralise it.
- Scanning a damaged print so it can be repairedResolution, bit depth, glass, and why 1200 dpi is refused here.
