There are many different film and slide scanners in the market. Also, price differences are quite high. What is the difference between those devices, which fit best for a specific user? This article will introduce some basic concepts to choosing the right device.
Amateur or professional?
First decision will be on the amount of pictures to scan. If this should be a professional activity, there are scanners in the market with automated feeders, even for sets of frame-mounted slides (in a similar way as slides' projectors).
This is really useful when the number of pictures will be high, either for archiving or to recover old picture collections.
Alternatively, amateur scanners are planned for fewer scans, 35mm slides or negatives are typically mounted onto trays or holders, and feed is made manually. Recently, a new generation of film scanners is entering the consumer market with great force, those are based on direct photography of the back-lit film, and they offer "scan" times of just a few seconds.
Resolution, density, gamma
Of course, imaging performance will be one of the most critical topics to consider. Since photo negatives or slides are small, high resolutions are required. In standard 24 x 36mm format, resolutions around 1,800 pixels per inch will achieve about five to six megapixel images.
If bigger sizes are needed, resolutions up to 7,200 ppp can be found in standard film scanners (being 3,600 ppp usual values). Surely, this will produce much bigger files!
Also, colour depth and sensor sensitivity are important. Here,
12-bit per channel (RGB) are recommended, 16-bit per channel is ideal to obtain RAW-like performance.
Gamma This will also define the gamma, the practical difference between the clearest and darkest points with still some image information (texture) visible.
Formato de salida, procesado
Finally, the capability of the scanner and the included software to process the raw data to eliminate dust, scratches, to find the right white-balance point and to export to the "right" file format may also be useful for some users. TIF or RAW files and JPG 16-bit per channel output can be stored in TIF or RAW files, whereas JPG will only need (or support) 8-bits per pixel. The first option is good for archiving and collection storage, the second one is best for everyday use and Internet publication. Bundled software Bundled software may also help in the final purchase decision, but the optical characteristics (resolution) and the processing power (scratch removal) should go first.