What’s the difference between interpolated and optical resolution?

You will often see that manufacturers quote the “Interpolated” resolution that will appear as a higher figure than the optical resolution this figure means that the extra resolution is being generated artificially by the software. The optical resolution is the maximum real resolution that your scanner can scan at. The interpolated part literally means that an intermediary value is placed in-between real pixels, in effect the quality will not improve but you will end up with a larger image that contains more pixels. Technically you may be able to enlarge the image without so much pixilation but the image will appear more “fuzzy” as sharp edges are lost.

When you do compare a scanners specs always make sure you are comparing like for like to ensure a fair comparison.

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What is infra-red cleaning or “Digital ICE”?

Infra-red cleaning is a term that refers to the use of infra-red light to detect dust and scratches on your film’s surface. The process works by scanning with an additional channel along with the normal red, green and blue ones; this infra-red channel will travel straight through normal cellulose film, while the IR light will pick up dust and scratches on the surface. With this information the scanner is able to locate any damage and using the pixels around the damaged area will be able to “in-fill” to create an image with no obvious dust or scratch damage. This method is very useful if you have many slides; as extensive cleaning of each one will be very time consuming.

Digital ICE (Digital Image Correction and Enhancement) is a very common infra-red cleaning brand name that can be found on many slide scanners, this was developed by Kodak but licenced to many top slide scanner manufacturers like Epson, Nikon and others. Other manufacturers have developed their own versions for example Canon with FARE (Film Automatic Retouching and Enhancement) and LaserSoft Imaging with iSRD Dust and Scratch Removal.

Be aware that infra-red cleaning may not work on all types of film, if used on some black and white film with metallic elements for example (most colour and chromogenic film will be fine but always check with the manufacturer)

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How much should I pay for a slide scanner?

This obviously depends on what you require from your final images and what you will be using them for, but as a rough guide you can pick up a basic slide scanner from between £40-£100. Basic slide scanners can produce some very good results but they tend to be aimed at individuals that need to convert a home collection, which means limited ability to enhance and edit. If you do want to upgrade and use features such as infrared cleaning and improved colour correction prices will start from around £160. Top end scanners will feature very high optical resolutions coupled with high end components like full spectrum light sources and high quality loading systems. These high end products will be found ranging from £250 upwards to thousands of pounds.

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