An insight into film scanning and manufacturers’ claimed resolutions
by Jonathan Bourla (www.jonathanbourla.com)
For some time when reading photo forums on scanning, I have realised how ignorant many people are about the scanner manufacturers’ claimed resolutions for their products. One time when offering up a response to a question regarding scanning, the subsequent answer to mine suggested I “upgrade” my admittedly long in tooth and out of production scanner with a new one with significantly higher resolution capability. What this person didn’t grasp is what I am going to address below.
My first film scanner was a Microtek i900. This scanner could scan film formats from 35mm through medium format up to 4×5 inch. The scanner was to be used to digitize my 4×5 inch black and white negs, plus the occasional 6×7 cm negs from my Mamiya 7 camera.
The box for my i900 scanner touted resolution of 6400×3200 pixels per inch. What I found out subsequently was that the scanner had two scanning arrays, separated by half a pixel. Each of these was 1600 pixels per inch, and to get higher resolution than that the second array came into play, providing in theory a maximum resolution of 3200 pixels per inch. Note the “in theory”. I did a test scan at 3200 pixels/inch, and found the result no better than a scan at 1600 pixels/inch followed by interpolation in Photoshop. In other words, you got a lot more pixels, but the actual resolution was no better than the lower scan. I have seen a review of a different scanner by photo-I-uk which found exactly the same effect. Their reviewed scanner was an Epson with an advertised resolution of 4800 pixels/inch, and they found the optimum resolution was actually 2400 pixels/inch. So I quickly came to realise I should scan everything at 1600 pixels/inch.
This shouldn’t have been a surprise to me anyway if one looked at Microtek’s scanner lineup, the scanner just up from mine was the 1800f, which as the model name suggests, this time accurately, promises a maximum resolution of 1800 pixels/inch. The difference between this model and my own was the more expensive one used a single scanning array.
Fast forward a while, and I had the opportunity to buy a demonstration use only Microtek 2500 from the Microtek dealer/importer. This was quite an old model, using the SCSI interface (which discovered what preceded the current USB that we all know). I needed to use an early series Mac computer. The computer died once, with the power supply failing. Finding it was impossible to locate a replacement, I decided to use a standard computer power supply (and a second power supply needed to power the Apple screen) and with them sitting ontop of the computer box, with the numerous wires diappearing into the box through a less than perfect hole in its top. Now when I think about itI can’t believe I did this modification to the computer, and for some reason would have been probably too scared to do that today if the need arose.
The scanner produces marvellous scans. I read a review of my scanner on View Camera magazine which confirmed it produces a resolution close to it’s specified 2500. Recently, with my belongings (including scanner) in storage while my wife, my elderly dog, and I have been on an adventure travelling around the New Zealand’s South Island, partly on a photographic project. I got some films scanned by an Australian firm using an Imacon scanner. The scans do indeed seem very good, but I would rate them as similar to scans I’ve got from my Microtek 2500.
If you think I have a wonderful scanning experience with my 2500 scanner, you’d be wrong. I am afflicted by the computer and/or scanner freezing, more often than I would like – obviously I don’t want it to happen at all! I am using scanning software called Vuescan, which is marvellous in that it supports a huge number of scanner models. I don’t know if I were to get the latest version of Vuescan whether it would be better, or just the same. Silverfast is a competitor. A version of it came as standard with my old i900, but unfortunately this wasn’t the case with my 2500. I’ve looked into getting Silverfast for my scanner, but it seems very expensive, and not knowing if it will be an improvement, I am reluctant to try it. I did notice they may offer trial versions, so I will have to go back to their site to investigate.
When I looked into getting the Imacon scans carried out while I didn’t have access to my own scanner, I also considered drum scans. There were several places that I contacted. They were all phenominally expensive. Also, they were all 8 bit scans, whereas I wanted 16 bit scans. If you are looking to do significant work in Photoshop or alternative photo editing program, then I consider it important to have the original scans done in sixteen bits. So this ruled out the drum scans. In the end I was very happy with the Imacon scans.
So to sum up, be very wary of the scanner resolutions promised by the manufacturers. A scanner offering 4800 or higher pixels/inch may actually really be one of 2400 pixels/inch. There’s nothing wrong with such a figure, but it’s nice to know what you’re getting, and comparing like with like.