During the years I had my dark room (the real thing), I remember I had to burn areas to get a better exposure across the photo. It was the analogue version of trying to achieve a high dynamic range — high enough at least to represent most brightness values across a photo based on what the film emulsion was capable of.
Today, with a scanner, the dynamic range of any scanned photo is not just limited to capabilities of the film emulsion but also by the dynamic range of the scanner itself. It’s as with digital cameras: there are only as many f-stops available as the sensor will “see”. Just as with digital cameras, you can achieve a higher dynamic range by combining an exposure for highlights and one for shadowy areas. This method works only with scanners that allow this “manipulation” and the right software to work it. SilverFast is by far the best application with which you can apply this technique, having been awarded the European Digital Press Association’s “Best Colour Management software of the Year” prize in 2008 for it.
In October the experts of scanner software SilverFast, LaserSoft Imaging, published a press release announcing the latest version of the Canoscan 9000F Mk II scanner has the software hooks to work the scanner in various high-end ways. More importantly, the inexpensive Canoscan 9000F Mk II can be manipulated by SilverFast 8 to increase its dynamic range from 1,379 greyscale values to 9,550, using SilverFast’s Multi-Exposure feature.
I was very interested in this announcement as I have seen what it’s capable of with a more top-end scanner such as the Epson Perfection V700. I wanted to know how difficult it would be to get the extended dynamic range from the Canoscan 9000F Mk II and what the results would be like.
How Multi-Exposure works
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Multi-Exposure is a patented exposure blending technique developed by LaserSoft Imaging. It is meant to be used when scanning slides, negatives and film strips. It is an absolute necessity when scanning Kodachrome film, with its dynamic range of 3.8, which exceeds most scanners’ capabilities.
Few of us, myself included, realise film has often been made up of multiple layers with different photo-sensitive characteristics. The way high-quality negatives like those made by Kodak, Fuji and Agfa were made, enabled photographers to shoot scenes with a dynamic range of up to 12 f-stops, while an ordinary slide film could easily cover eight f-stops.
Many scanners cannot capture this dynamic range, which results in a conventional scanning operation losing image detail.
SilverFast’s Multi-Exposure functionality scans the original twice, each time with a different exposure time. The multiple scans that are obtained are combined by the software in an image that is effectively a High Dynamic Range (HDR) image. It’s the same type of HDR image we all know from bracketing shots with our digital camera and then processing them through an app like Photomatix or Hydra Pro. An additional advantage of Multi-Exposure is that it will also reduce noise.
Multi-Exposure only works with transmissive originals and with the Canoscan 9000F Mk II, I observed the scanner making two exposures.
Experiencing Multi-Exposure scanning
In theory, Multi-Exposure scanning with SilverFast 8 should be as straightforward as scanning an original only once.
I tested the Canoscan 9000F Mk II with SilverFast 8 using an ordinary scan first, then repeating the scan operation with Multi-Exposure afterwards. All originals were scanned at 300 dpi, with a scanner resolution of 300 ppi. If I were to print a photo, this combination would give me an output the size of a DIN A5 print.
A higher resolution would theoretically increase detail, but unless you’re printing a book on a printing press, 300 dpi is all you need. The increase in detail of a 1200 dpi (or higher) scan goes lost in the resolution limitations of most printing devices, including large format photo inkjet printers. It adds data to your file, making it bigger and more unwieldy to process, but none of it would be visible.
However, an increase in the dynamic range should be visible regardless of the output resolution.
With SilverFast 8 you can scan in two ways: you can either set up the software prior to scanning anything, using sets of defined parameters. These will be used by the Workflow Pilot and reduce the scanning operation to what is essentially a one-button operation. As you can include the Multi-Exposure setting in a Workflow Pilot preset, the Multi-Exposure benefits can be had with the click of one button. The reason why you would want to do this is that Multi-Exposure does take longer than making an ‘ordinary’ scan. That’s normal as the scanner needs to make more than one exposure and the software must process the subsequent HDR image. Including Multi-Exposure in a Workflow Pilot preset will speed things up as the software and scanner don’t have to wait for your input anymore.
Alternatively, you can set all parameters manually for each individual scan, including Multi-Exposure.
The Workflow Pilot is very easy to use. It only demands you to make five choices and then hit the Play button. You need to select the task (the preset; by default SilverFast comes with the most commonly used scanning outputs, such as
Web, print or social share), the resolution, the scan type (Reflective or Transmissive) and the scan format (HDR, 24-bit…). The predefined parameter settings will do the rest.
Personally, I like to tamper with the scanner settings in SilverFast. That allows you to get a perfect scan before you load it into Photoshop for further creative editing of the image. You shouldn’t try to remove dust and scratches in Photoshop, but do it in SilverFast as the latter provides for a feature called iSRD. iSRD uses your Canoscan 9000F MK II’s infrared lamp to find dust and scratches and fix these automatically (and much faster than “ICE”, which you’ll find in some other scanners).
The results of a Multi-Exposure scan
The Multi-Exposure feature does not necessarily result in a more detailed shadow or bright area. Depending on the scanner, it can also mean a more balanced representation of the greyscale and colour values in-between, or everything wrapped into one.
With the Canoscan 9000F Mk II, I noticed slightly better shadow details and a quite noticeable richer colour representation of the (one tone darker) primary colours when scanning positive slides. You can see this on a well calibrated monitor yourself by downloading (right-click and select “Save As…”) these two test slides.
For negatives I didn’t have such test patches available, but in general you may expect better shadow details with negative film that goes beyond the already quite high dynamic range of the Canoscan 9000F Mk II.
The effects of the Multi-Exposure technique are visible when scanning to 24-bit files, but to get the most out of them I recommend using SilverFast HDR Studio after scanning to 64-bit HDRi. This application is the only one capable of decoding all information (including infrared data), effectively delivering everything needed to archive your analogue photos and to convert them into perfect prints or digital files.