Another type of scanner is a Film Scanner. As its name implies, it serves the dedicated purpose of scanning film (slides, negatives, etc.). Many wonder why it is necessary to purchase a dedicated purpose scanner for film, especially when there are Transparency Media Adapters (TMA) available for flat bed scanners. The primary reason is higher resolution and dynamic range.
Film is loaded with microscopic detail, far beyond that of printed media. Obviously, this detail is necessary in order to allow for the extreme magnification (enlargement) to which this media is subjected.
A good flat bed scanner has a resolution of 600ppi. Some better ones even meet or exceed the 1000ppi mark. However, a dedicated purpose film scanner for 35mm film features resolution in the neighborhood of 2700ppi - 2800ppi.
Film typically exhibits more tonal detail than printed media, therefore, more dynamic range is required in a film scanner to capture this detail that would otherwise be lost.
One thing to consider when thinking about purchasing a film scanner is color correction. When you scan a photograph on a calibrated flatbed scanner, you are simply duplicating the work of the lab that printed it (color correction, density, contrast of paper, etc.). However, when you scan film, you will need to adjust/correct these factors. Color correction can be a very challenging topic to many individuals, especially if you do not have color printing experience.
Film scanners are available in three basic size ranges: 35mm only, sizes up to 6cm x 9cm, and sizes up to 4" x 5". The price increases 2X - 3X with each category.