Scanning a damaged print so it can be repaired
Almost every disappointing restoration was decided at the scanner rather than at the repair. The print is the only original, the scan is the only thing any software will ever see of it, and a scan made with the defaults on has already thrown away the range and added marks of its own. Ten minutes of attention here is worth an hour of anything later.
The six settings that matter
- Clean the glass, not the print. A microfibre cloth and breath on the platen. Every speck on the glass is scanned at full resolution and lands in the detector's lap as damage — which it will duly mark and fill, softening real picture in the process. The print itself gets a soft brush at most; a damaged emulsion comes away on a cloth.
- Switch off everything automatic. Auto exposure, auto colour, auto contrast, backlight correction, unsharp masking, descreening. Each one makes an irreversible decision on the way in and the good ones make it badly on a faded print. A flat, dull scan is the correct input here; it has more range left in it than a scan that has already been corrected.
- Choose a resolution from the print size. 600 dpi is the right default for a print you intend to repair. It resolves more detail than a domestic print from the 1970s ever held, it keeps the file inside what a browser tab can hold, and it makes a hairline scratch three or four pixels wide — which is the width this page's fill is built for.
- Scan at 8 bits unless you have a reason not to. 16-bit is worth having if the print is badly faded and you intend to do the tone work in desktop software. Here it is reduced to 8 bits on the way in, so it buys you nothing and costs you double the file size. Colour, not greyscale, even for a black-and-white print: the damage often sits in one channel.
- Turn the infrared dust removal off. Digital ICE and its equivalents find dust by shining infrared through the material and looking for what blocks it. That works on colour film, whose dyes are transparent to infrared. It does not work on a silver-gelatin print, whose silver blocks infrared exactly as the dust does — so the hardware marks the picture as dust and smears it.
- Save as TIFF, and keep it. Uncompressed TIFF is what scanner software writes best and what opens here without a generation of JPEG loss. Keep the raw scan untouched and work from copies. It is the only original you will ever have, because the print will not be less damaged next year.
Why this page turns away a 1200 dpi flatbed scan
A scanner quotes resolution in dots per inch, which is a statement about the paper, not about the file. Multiply it out and the file sizes are larger than most people expect — and the limit that bites is not disk space but what a browser tab can hold, because repairing an image means holding several full-resolution copies of it at once: the scan as it arrived, the working copy, the mask, and the result.
| Resolution | Pixels | What happens here |
|---|---|---|
| 300 dpi | 1800 x 1200, 2.2 MP | Opens immediately. Thin for repair work |
| 600 dpi | 3600 x 2400, 8.6 MP | The recommendation. Comfortably inside every limit |
| 1200 dpi | 7200 x 4800, 34.6 MP | Over the soft cap: a lighter working copy is offered |
| 2400 dpi | 14400 x 9600, 138 MP | Over the hard cap. Refused, with the resolution to use instead |
The soft cap is a question rather than a refusal. It offers to work on a copy no more than a set number of pixels on the long edge, tells you that anything you save will be that size, and leaves choosing a different file as an equally weighted second option. The hard cap is a genuine refusal, and it names the scanning resolution that would have fitted rather than simply saying no.
What 600 dpi is actually resolving
A colour print from a high-street lab in 1974 holds detail on the order of ten to fifteen line pairs per millimetre at best, and usually less. 600 dpi samples at about twenty-four pixels per millimetre, which is comfortably past the point where more resolution is recording the surface of the paper rather than the picture on it. Scanning higher makes the grain and the paper texture larger relative to the damage, which makes detection harder, not easier.
Photographing a print instead of scanning it
A phone photograph of a print is a real intake path and it is not a second-class one, provided two things are true. The light has to be even and off-axis — a window to one side, not a flash, which will put a specular blowout in the middle of the photograph you are trying to rescue. And the camera has to be square to the print, or the result is a trapezoid that no amount of repair will straighten.
What you lose is flatness of field and a known scale, and what you gain is that it takes ten seconds and does not involve pressing a fragile print against glass. For a print that is already torn, the second consideration can outweigh the first.