Digital acquisition of slides
Until a few years ago, when information technologies had not yet become the absolute rulers of the photography scene, slides were among the media most used by professionals. In recent years the analogue film market has undergone a real collapse, to the point that many manufacturing companies have decided to definitively send the production of these analogue supports to the attic. Nowadays practically all photographers, both professional and amateur, have switched to digital cameras but it is not uncommon for there to still be "old" slides at home or in the shop. In these cases, to be able to work on photo editing or simply to have your shots on the computer, it is possible to proceed with digitizing the slides. To do this, special devices are used, namely slide scanners , which allow the acquisition of images and their conversion into digital format. Since the slides are small (only a few centimeters on each side), for digitization to give quality results the scanner must have a very high resolution. Generally we start from 2000 dpi (dots per inch) up to, in the more expensive models, even 4000 dpi and above.
How does it work
The cheapest models of slide scanners are only able to acquire images from 35 millimeter formats, while you should opt for higher priced models when dealing with other formats. These models with superior technological content are equipped with interchangeable magazines of different formats, in which to place the slides to be scanned. The acquisition of images does not take place, as in the case of traditional scanners, starting from reflected light, but rather from the light that is projected by the scanner through the film or photographic negative. The light is captured by an optoelectronic unit, transformed into digital format by an analog-digital converter and finally sent to the computer connected to the scanner. Generally, in models with basic functionality the slides are loaded by hand one by one, or at most in blocks of five, while in scanners for professional use it is possible to perform automatic scanning directly from the loader. In many cases, slide scanners are combined with dedicated software which allows you to correct, simply and quickly, any damage to the film (for example scratches or stains) but also chromatic alterations due to incorrect development of the slides or simply passing weather. The device on sale does not always come with its own software, but there is no shortage of free programs online (such as Gimp) with which to achieve the same result.
How to choose a slide scanner
Slide scanners are sometimes quite expensive devices, and the purchase of one model rather than another must be carefully considered. For example, if you only need to digitize 35 millimeter slides, a standard scanner is sufficient, while in the presence of different formats it is necessary to take a higher sum into account. Another very important parameter to evaluate is the speed of acquisition of the slides. Generally, the higher the resolution (in dpi) of the scan, the longer the scanning will take. This aspect may be negligible if there are not many slides or negatives to be digitized, but when we are talking about a considerable amount of images it is essential to choose scanners with high performance in terms of speed. The compatibility of the scanner driver with the computer operating system must be checked in advance: to do this simply consult the technical specifications. Generally, slide scanners, as well as computers, are equipped with USB 2.0 ports but even in this case it is a good idea to check their compatibility. If you plan to work with high resolution scans, you must take into account a considerable use of RAM by the computer, therefore the technical characteristics of the hardware must be sufficient to support image management. The most recent computers usually have at least two or four GB of RAM, so in theory there are no problems, but pay attention to PC models that are already a few years old.
Where to buy
In many electronics and photography shops you can find slide scanners, although the internet is now king when it comes to purchasing technological devices. On the web it is in fact possible to read up on the technical characteristics of the scanners, make comparisons between the different models and take advantage of the most advantageous purchasing conditions. Here, in this regard, are some of the main manufacturers of slide scanners:
- Plustek : http://plustek.com
- SVP (Silicon Valley Peripherals): http://www.svpcam.com
- Veho : http://www.veho-uk.com
- Kodak : http://www.kodak.com
- Pacific Image : http://www.scanace.com
As regards the purchase prices of slide scanners, the range is quite wide and influenced both by the manufacturer's brand and by the technical characteristics of each device. The simplest scanners, in which you insert one frame at a time, are quite cheap and generally a cost of around forty euros is enough to take home a good quality one. Prices undergo a notable increase when the scanner is equipped with a trolley on which to insert multiple slides for a sequential scan: in this case prices can be around 70-80 euros. Finally, scanners capable of automatically managing the digitization of slides contained in a magazine can have prices even higher than 300-400 euros.
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