Restoration work lives or dies by the quality of the original digitisation. If you start with a poor-quality file, a poor-quality file is all you’ll ever have.
These are the parameters I use for my work:
You must scan in 16 bits per channel. Depending on the scanning software, it might be called “48-bit color” instead (three channels of 16 bits each = 48 bits).
8-bit (or “24-bit”) isnt robust enough for restoration work. Well, maybe if the old photo is in very good condition, and not require much editing work, 8 bits per channel might be enough. But if any degree of fixing is required, you need all of that high-bit data to play with.
If your photo needs some or a lot of work, and your scanner can’t scan in 16/48 bit, stop reading right here, and photograph your photograph instead.
If you’re working with slides, seek the services of a slide scanning shop, or buy yourself a good scanner which can scan slides in 16/48 bit.
Scan in full color, even if the photo is black-and-white.
Do not apply any sharpening during the scan.
If your scanner offers noise reduction or speck removal functions, try them. Scan with and without them, then analyze the results in Photoshop afterwards (at 100% view of course) and decide which is the best file to work with.
It goes without saying that you should scan in sRGB.
It’s not a bad idea to leave a little bit of extra room around the photo, to allow you to crop or rotate or clone as necessary later.
If at all possible, dont clip the highlights or shadows. Leave a little bit of space at each end of the histogram. Not a whole lot, just enough to give you some latitude when editing. Its better to start with a slightly flat image than an over-contrasty one.
Save as Tiff or PSD – either is fine. But not Jpeg (since Jpeg files can only be 8-bit).
SIZE AND RESOLUTION
In most cases, I like to work with files that are around eight megapixels. So I scan the photos (prints or slides or negatives) at 100% size, at the following resolutions:
- If the photo is 8×10 inches or larger, scan it at 300ppi
- If the photo is approximately 6×8/6×9, scan it at 400ppi
- If the photo is approximately 5×7, scan it at 480ppi
- If the photo is approximately 6×4, scan it at 600ppi
- If the photo is approximately 3×5, scan it at 720ppi
- If the photo (or slide) is 2×3 or smaller, scan it at 1200ppi