Slide/Film Scanners

What to Look For by Norb Veit 3/23/2004

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There are a number of critical features which you should consider when buying a film scanner. Here are several to think about.

 Resolution

My recommendation is to look for one which has about 4000ppi/dpi. While some scanners offer higher resolution it is important to note that film grain and scanner interpolation algorithms begin to limit the “meaningful” resolution of your image. As an example, once film grain exceeds 2.5 ten thousands of an inch, your scanner is down to reading film grain.

 Focus

Scanners have to try to focus on your film in order to set the focal distance from the scanning sensor. Typically, the default focal point chosen by the scanner is near the center of the image. Just one problem, the scanner tries to focus by trying to lock onto an edge. If there isn’t a sharp well defined edge at the center of your image, the scanner may not get the best “lock”. So wouldn’t it be nice if the scanner would allow you to tell the scanner where it should try to do its focusing? Therefore, it's a good idea to determine if the scanner you are thinking about buying, has a “manual” focus capability.

 Multi-Sampling

Scanners are subject to electronic “noise”, i.e. sometimes they see something that’s not there because of tiny power variations within their circuitry. This is much more likely to occur when the sensor is focused on a dark area in the image and there really isn’t anything for the sensor to see. To reduce the amount of power variations at any given location, some scanners can sample the same location from 2 to 16 times. This extra sampling is averaged so an occasional power variation is averaged out. Essentially, multi-scanning cancels out the noise which is prevalent in the darker areas of a scanned image.

 Digital-ICE

Often, there are minute amounts of dust (even if you use canned/compressed air to dislodge them) and maybe even some tiny scratches on your slide. While you can repair these imperfections once you get the digitized image into Photoshop, it can be a time consuming (30 minutes per image) process to hunt down all the specks and clone them out. Digital-ICE is a patented technology which automatically removes the specks and scratches without degrading the overall sharpness of your image. Do yourself a favor, get a scanner with a good implementation of Digital-ICE.

 Histogram Adjustments

Look for a scanner which has not only the ability to alter the light curve histogram of your images, but one with a graphical display that is large enough to be able to make precise adjustments. This is especially important for setting the black points and white points of your image. By modifying the histogram as part of the scanner workflow, you can get more tonal information out of your image than if you leave your scanner set to automatic mode.

Batch Scans

This isn't a really useful feature since you are allowing your scanner to pick the focal point, ignore the histogram and utilize multisampling on every image (which greatly lengthens the time it takes to scan each image). While batch scanning might seem like a great convenience, you’re really doing a dis-service to your carefully exposed, composed and crafted images when you let a machine try to make subjective decisions about your image.

 Good luck in your purchasing decision. I hope this article helps to clarify some of the important features you should consider before making your purchase