High Dynamic Range Scanning

Better scans using SilverFast Ai Studio software and the Microtek ArtixScan M1 scanner

By Paul Schranz Back to

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The secret to quality scanning is getting the most data possible from the original. The dynamic range, even from high-end scanners, usually requires a compromise with either the highlights or the shadows. A low-end scanner simply lowers the dynamic range so that neither are reproduced adequately. If you make adjustments to retain those light highlights, you end up severely blocking the shadows. When attempting to open them in Photoshop curves, all you accomplish is intensifying shadow noise. Now, however, there is a sensible solution that allows you to use multiple exposure scans in much the same way that HDR capture works on a DSLR. One scan is created for the highlights, another for the shadows. This is all created automatically using Microtek’s new ArtixScan M1 scanner and SilverFast’s Ai Studio software (which comes with the deluxe version of the scanner).

This is very different than multi-sampling that has been available on scanners for some time. Multi-scans essentially take several identical scans and then use artificial intelligence to reduce noise by eliminating erroneous aberrations.

How it works

Multi-exposure scans are actually a simple procedure. A frame of film is pre-scanned, and the full tonality is analyzed. Secondly, the scanner, instead of trying to manipulate the range of a single exposure, calculates two different exposures—one for the shadows and one for the highlights. This cuts the strain of trying to render both tonalities and also reduces the shadow noise caused by trying to accommodate both extremes in a single scan.

By using the ArtixScan, Silverfast, and multi-exposure scanning, there is no need for pre-scanned manipulation. In fact, all of the controls in SilverFast are grayed out when it is set to multi-exposure scanning.  As with Raw files in your camera, you do not reduce your scan to an 8-bit file, but stay in 48-bit color or 16-bit grayscale. In order to do an HDR scan, SilverFast must be launched as a stand-alone application. The image is then saved and can be opened later in Photoshop for further editing.

To demonstrate this process, I chose a 6×7 transparency that had a wide range of exposure from near white to near black, but still had slight tonality in both extremes. In Figure 1, you have a single scan made at 48-bits and automatically reduced to 24-bits by SilverFast. I used auto-exposure rather than trying to manipulate the pre-scan settings. The size of the scanned file was 90.9 MB. Look at Photoshop’s levels for this image (Fig- ure 2) and note the reduced dynamic range. Figure 3 is the same image made using SilverFast Multi-Exposure in 48-bit HDR mode with no manipulation of pre-scan settings. The file is essentially the raw scanned data, and weighs in at 185.47 MB. Figure 4 shows this file’s extended range and the overall depth of data now available to manipulate. With this huge increase in available data, I used Pho- toshop’s Curves and enhanced the image further (Figure 5). The image of a reflection in Monroe Lake, Indiana, at the beginning of this article was also made using the 48-bit HDR process.

This quality comes at the cost of both time and computer power. While multi-scanning is obviously a slower process than a general scan, it also yields superior output that makes the extended time worth it. If you’re thinking of trying it, consider the power of your computer and the amount of memory available to work with files of this size. The ArtixScan has a batch-scanning system that allows you to set multiple frames within the carrier to be scanned sequentially in HDR. When you batch scan, the image files are automatically saved in a designated folder and can be opened in Photoshop at a later time.

Artixscan hardware

The Microtek ArtixScan M1 offers some unique qualities besides multi-exposure scanning. This scanner isn’t a reflective scanner with pseudo-transparency capabilities; it actually transforms itself into one type of scanner or the other.

Some flatbed scanners simply add a light source above the glass plate to project light through, rather than reflect off of, the scanning material. This means that the light path is also projecting through the glass plate, causing some refractive distortion. The ArtixScan M1 has a dedicated light source and recording optical system below the glass in transparency mode, a system called Emulsion Direct Imaging Technology. It enables the scanner CCD lens to read directly off the emulsion side of the film without any other glass between the lens and the object scanned. There are essentially two optical paths, one for reflection and one for transparency. When changing the scanning mode, a mirror directs the selected optical path to the scanner CCD. My experience with medium- and large-format transparencies has shown some remarkable results.

The scanner captures images at 4800 ppi with an optical density of 4.4 using a Sony CCD sensor, and a consistent cold-cathode fluorescent lamp light source. The optics have an anti-reflective coating. The scanner is designed to scan 35mm, medium-format, and 4×5 film using precision focusing and rigid film holders. The reflective surface for flat scans measures 8.5×14 inches. The scanner itself measures 22.3×15.2×6.2 inches and weighs 26.4 pounds. It uses a USB 2.0 interface, and has a one-year warranty.

Calibration

Obviously, the collected software is only as good as the calibration of your scanner, and the SilverFast Ai Studio has its own calibration system built into the software. It uses included IT-8 calibration targets for both reflective and transparency. The target is placed in its transparency or reflective position. When you start the calibration process, a scan is made; the software automates the data collection by reading the bar code on the IT-8 target, compares it against specific target data and produces a calibration profile. When calibration is completed, you are ready to scan.

The ArtixScan M1 Pro with SilverFast Ai Studio software lists for $799.


About the Author

Paul Schranz
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Paul Schranz is a photographer and a photographic educator. He holds a BFA in photography from Ohio University, Athens, OH and an MFA in photography from Northern Illinois University, DeKalb, IL. He is Professor of Art Emeritus, Governors State University, University Park, IL, where he taught photography and digital imaging. He exhibits nationally and has received grants for documentary projects from the Illinois Arts Council. He is the former Editor of photo technique and Director of Mesilla Digital Imaging Workshops. Schranz is currently a faculty member at Dona Ana Community College, Las Cruces, NM, where he teaches advanced digital imaging, photographic composition, digital printing, image enhancement and manipulation.