How to scan negative and slide films

Scanner instructions



How to scan negatives & positive, slides & film

Chances are that somewhere in your family photo collections you have a bunch of slides and negatives that you wish you could do more with. You may want to include them in your family history, to publish them on the Web, or simply to make digital copies so you can share them with the family.

If you've ever tried to scan a negative or slide on a regular flatbed scanner, you'll know that it doesn't work, and you end up with a pure black scan. In this article we'll show you how you get your negatives and slides into digital format, and what issues you may face along the way.

Benefits Of Scanning Film

There are some key benefits to scanning film (we'll use the term to include slides and negatives) in comparison to scanning a photo. When you scan film, you can use the full area of the slide or negative, whereas a photo will generally only display a cropped portion of the original. You are also scanning the original source image rather than the color corrected and tweaked version of it that the photo processor has provided you with. The process of turning a negative image into a positive one involves inverting the colors in the image and removing the orange cast from the negative. This would be a complicated process if you were doing it by hand; however, your scanner will provide you with software to do this automatically, or you can purchase standalone software to do it.

Most cheaper flatbed scanners are designed to scan photos and other images that reflect light when it is shone onto them. The problem is that film is transparent and light passes through it rather than being reflected off it. Many flatbed scanners have an optional transparency adapter, which replaces the scanner lid with a larger box shaped object. The adapter provides a light source above the transparency, which shines light onto the film from above (rather than from below). The sensors pick up this light, letting you scan film successfully.

For purists, a transparency adapter is not an ideal solution because you still have a sheet of glass between the film and the sensors that record the light. Scanners built specifically for scanning film have no glass between the film and the sensors, and the light source is generally more intense.

Scanning a negative

Scanning a negative in a film scanner produces a more accurate image than scanning a photo in a flatbed scanner. This results in significant improvement in image quality. Film, although it is physically smaller, contains more detailed tones and can be scanned at resolutions of 2,400dpi (dots per inch) and higher, and you'll see the difference in quality.

Most flatbed scanners will offer a resolution of around 600dpi and an interpolated resolution of 1,200dpi. The smaller figure is the actual resolution for your scanner, and the interpolated resolution is the result of the scanner guessing or relying on software for additional information that it can't actually see to give you a larger resolution final scan.

So, if your flatbed scanner has a true resolution of 600dpi, let's look at what you can expect from scanning a slide or negative. The math is fairly simple: when you scan a 1-inch square negative at 600dpi, you will get an image measuring 600 x 600 pixels. The calculation is simply 1 x 600. Printed at an output resolution of 150dpi this will produce an image approximately 4 x 4 inches or half the size of a sheet of letter-sized paper, which is 8.5 x 11 inches. The calculation is 600/150 = 4 inches. At higher output resolutions, the final image size will reduce very quickly. For example, scanned at 600dpi and printed at an output resolution of 300dpi, the image will measure around two square inches.

If your output is destined for the Web where the display resolution is 72dpi, the results probably will be fine. The resolution may be too low for your print needs if you intend to have the results commercially printed at resolutions of 1,200dpi and higher.

The density of the image, or the measure of the contrast range in the image, also affects the scan results. A photo has a density of around 2.0, a negative around 3.0, and a slide around 3.6. The dynamic range of your scanner is a measure of its ability to represent tones in an image. Most flatbed scanners offer dynamic ranges suited to photos that will be incapable of extracting the full detail from a slide or a negative. This affects slides most of all because you won't be able to extract the full depth of tones from the darker areas of the slide. For negatives, this works in reverse, and the tonal loss will be in the lighter areas of the image and will be correspondingly less noticeable. So, you'll generally get better results scanning negatives with a transparency adapter than you will scanning slides.

Finally, a flatbed scanner with a transparency adapter is unlikely to offer any ability to focus the film, so you may find that some scans are out of focus and less sharp than they should be. Removing a slide from its mount may help you get a sharper scan.

High-Quality Scans

When you need high resolution and high-quality scans for printed output, you'll be best advised to invest in a film scanner (often also called a slide scanner), which will scan both negatives and slides.

You'll want a scanner that scans at a high resolution (2,400dpi or higher). When you scan a slide or negative at a high enough resolution, you can obtain results that offer much better quality than you'd get if you took a 4 x 6 photo made from the negative and scanned it.

Photoshop and Aperture

Once you've scanned your film or slide and created a positive from the negative, you can work on the images with the standard photo-editing tools, such as Adobe PhotoShop or Aperture. You'll find that most scanners come with some suitable photo-editing software.