For 74 years, Kodachrome set the standard for color accuracy and for longevity among slide films. Memorialized in song, thanks to rhymin’ Paul Simon, Kodachrome has a special place in the hearts of talented photographers everywhere.
Kodachrome wasn’t just different because it was the first popular color slide film, although it was indeed the first. Kodachrome was different because, unlike other slide and color-negative films, Kodachrome films didn’t incorporate dye couplers in the emulsion layers. These couplers -- which give film its colors -- were added during the extremely complex film-processing stage. As a result, Kodachrome emulsion layers are thinner than other film types, so less light is scattered upon exposure. This helped the film garner its reputation for sharpness and for color fidelity.
For scanning slides to digital, it’s useful to know some of these basic traits, because they can affect the quality of the scans. Like other 35mm films, Kodachrome images can be scanned at very high resolutions, but that’s where the similarities end. For one thing, the film has a tendency to scan with a slight blue cast; some scanning software, like SilverFast from LaserSoft Imaging, have special Kodachrome color profiles to hand this situation.
There some different approaches to converting slides to digital. Some people advocate a practice of scanning slides at the highest possible resolution, with no cleaning of scratches and debris. This acts as a digital “record” of the slide frame as it is, which is valuable for documentation or historical purposes. Most personal photographs, however, do not need this level of preservation, so they should be as dust- and scratch-free as possible as the scan is performed, so each time it is reused, defects won’t have to be removed.
ICE, ICE baby...
Most modern film scanners use an infrared channel to detect defects, fingerprints and dust which are then highlighted on a “defect layer” which can be removed. Kodachrome, however, interacts with this infrared channel differently. First, due to the absorption of the cyan dye extending into the near infrared region, the cyan layer is opaque to infrared radiation. Second, Kodachrome’s relief image (on the emulsion side of the film) can affect the infrared channel and cause a slight loss of sharpness.
The technology used to detect the infrared layer is usually called “Digital ICE”, and can be turned off or adjusted to accommodate Kodachrome. Make extra sure the film is clean before scanning or you will be spending a lot of time cleaning up dust spots and scratches in Photoshop.
If your slide collection contains a mixture of Kodachrome and other slide films, be sure to first group them by type of film. That way, if you have to make workflow adjustments based on film type (turning “Digital ICE” on and off, for example), it will consume less time.
Also, group your horizontal and vertical shots into separate batches, then scan each batch individually. This will reduce the need for post-scan rotation of the digital images.
Photo Credit: Flickr