Slide Scanner Guide

What you need to know about slide scanners before you buy…

If you’re going to invest in a slide scanner it’s beneficial to have a basic understanding of what all the technical jargon actually means and an understanding of how the products work; that way you can work out exactly what you require from the scanner.

What is a slide scanner?

A slide scanner is a desktop device that is designed specifically to scan slides or negatives and convert them to a digital format.  They can be connected directly to a PC or, in some cases, will scan directly to a removable memory card.

What’s the advantage of going digital?

Unfortunately it’s a fact that film will fade over time so if you want to preserve your memories and stop the damage that will inevitably happen then going digital is the only way. With a high resolution scan you can capture that slide and preserve it properly without the risk of fading and colour drain associated with film.

Another advantage is storage, the size of a large archive of scans can be huge and storing them can be a real problem if space is tight. With digital you can store them all on your computer, enabling you to send images to print or just as easily the other side of world with a few clicks of the mouse.

As if that wasn’t enough, digital files also allow you to make corrections to your images, so you can bring your photos back to life and retouch any colour loss or other damage.


What kind of slide do you have?

35mm negatives are the most common form of photographic film and are generally in one of two formats: an uncut strip of film or mounted in an individual case.

Mounted slides are normally held within a 2”x2” mount; this can be plastic or cardboard. But be careful; not all slides mounted in a 2”X2” mount are 35mm. Other film types include 110, 126 and 127 so check the specs as with larger film some scanners may crop parts of your image.

35mm (135) Format: This is the most common format of film. The film measures 36mm x 24mm and will be mounted in a 2”x2” mount.

110/ 16mm “Instamatic” Format: This is a much smaller film at around a quarter the size of standard 35mm film and will be mounted in a small aperture 2”x 2” mount with a film size of 13mm x 17mm.

126 “Instamatic” Format:  This film was introduced by Kodak in 1963, with a square frame of 28mm x 28mm.  At a glance they can sometimes be confused with a 32mm slide; they come in a 2” x 2” mount.

127 Format: A square film size of 38mm x 38mm, mounted in a 2” x 2”.

127 Superslide: A larger 127 format with 40mm x 40mm film. This type of slide is much rarer.

Film and slide terminology

Transparency: refers to a photographic image that is in a positive form on a transparent base. This means that when light is shone through the image will display correctly. Transparencies are intended to project the image being held.

Negatives: Most old film cameras will capture images onto a negative film. The negative image found on the film is an inverted version of reality in which light areas will appear dark and dark areas as light. The colours in the film will also be reversed meaning that greens will appear red; blues appear yellow and so on.

Slides: This refers to an individually mounted section of film (normally a transparency) intended for projection onto a screen using a slide projector.

Frame: Refers to one still image. This can be in a multiple frame filmstrip or on its own.

Filmstrip: A section of photographic film containing one or more frames.

Film Format: The size of the film.

Monochrome: This refers to a black and white film.

How does a slide scanner work?

A slide scanner works by shining a light through your slide or negative and recording the image through a sensor; some may also use special lenses to improve quality. There are a number of key elements that will determine the quality and overall ease of use, below is an explanation of the main components.

The light source will vary depending on the model with the higher end models using RGB LED array lighting that is quick to warm up, provides a high quality light and will run at lower temperatures. The other form of bulb is a florescent, which will need to briefly warm up before giving a constant light.

The sensor is the part of the scanner that records the image. It converts the light being shone though the slide into a digital signal. The types of sensors likely to be found on most slide scanners will be a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Both types are capable of equally good quality but function in a different way: CCD will convert to a voltage output (analog) and are less complex in design. CMOS will convert each pixel to a voltage but will transfer through amplifiers and digitization circuits and output a digital file.

An Infrared lamp may be found on higher end scanners, this enables a form of dust and scratch removal called infrared cleaning. This process works by scanning the slide with an additional infrared channel which will pick up the areas that are blocked by dust or scratches. By automatically overlaying the infrared information with the visible image the scanner will know what areas are damaged and can “in-paint” the tarnished area. An example of this technology is Digital ICE (Image correction and enhancement) which is a common brand you will hear

Scanning software is an extremely important part of the scanning process and can have a big impact on the quality of image. It is the software that will determine a number of key elements within the file. One such element is the colour reproduction of the digital image which is controlled by selecting the correct film profile on your software. It will then apply certain colour bases and other details so it is important to always select the right profile for your particular slides e.g Kodacrome or Monotone

Any dust and scratch removal settings will be taken care of by the software, although it is the infrared scan that indicates where affected areas are it’s the software that will fix it. Obviously, the more sophisticated the software, the better the final image will look and the more flexibility to adapt areas that don’t come out as well as expected. Vuescan or Silverfast are examples of software that will often do a better job than the manufacturers bundled software.

The slide carrier or feeder is the component that holds your slides or filmstrip and is subsequently placed in the scanner. Carriers sometimes hold a single slide, while other carriers support the placement of multiple slides for sequential scanning. Carriers can be made of either plastic or metal.
Most slide scanners will come with a carrier for both mounted slides and filmstrip. The carrier either moves the slide over the light source and sensor assembly or moves the assembly over the slide. The carrier is either moved automatically with a motor or on the more basic models this will be done manually.

Automatic slide feeders will be found in the form of an add-on device or a built in feature that will automate the process of feeding slides into your scanner. Most feeders will be capable of loading about 50 slides at a time and can be left alone while they work their way through your archive. There are not a great number of add on slide feeders on the market and the ones that are, will inevitably only be compatible with their corresponding branded scanners.  Some high end scanners like the Braun Multimag Slidescan  scanner or Pacific Image PowerSlide have built in feeders. An automatic feeder is a highly advisable feature if you have a large archive to get through as it can be extremely time consuming to scan individually.

Can I use my flatbed scanner for slide scanning?

Yes you can, it is possible to use a flatbed scanner but it will greatly depend on the quality of the product and if it has the right slide or film holders to make it a worthwhile task. Higher end flatbed scanners come with adaptors and holders to mount your filmstrip or slides. I wouldn’t even try using a flatbed that doesn’t come with a mount because having the film “floating” on the slippery glass will more than likely result in poor scans.

The thing to be aware of when scanning on a flatbed is that most systems (unless you really spend a lot) will not have a user controlled focusing system. This means that when your mounted slide sits on the glass, the surface of the film it is raised by a small amount which can sometimes mean a slightly out of focus scan.

Additionally, you have to bear in mind that a flatbed has not been specifically designed for the job so issues like scanning through a layer of glass and being designed with printed materials in mind (lower resolution) will compromise some areas. In my opinion, a standard flatbed will be adequate for low quality outputs like web with resolutions of 72dpi or basic reproductions. Although flatbeds are capable of slide scanning, if you are looking for high quality output from your negatives or transparencies, my advice would be to choose a dedicated slide scanner for the job which will give you more in terms of resolution, speed and certainly quality.