A note on the context of this document

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Creating linear scans with SilverFast SE or Ai

Another scanner software that enables you to create linear scans is Lasersoft Imaging‘s SilverFast SE or Ai. To create a 16-Bit linear scan start by selecting the "General" tab. There you need to set the "Scan Mode" to "Normal (File)" and to select "Positive" from the drop down list next to "Pos/Neg”.

As a second step navigate to the "Frame" tab. Here you need to define "48 Bit HDR Color" to be the "Scan Type". All Image editing choices will be disabled after doing so. SilverFast now operates in its RAW mode. The resulting Tiff files contain linear intensity values as are being read in by the scanner and as is required for negative conversions with ColorNeg.

The Gamma setting in SilverFast usually does not influence HDR scans at all. The files recorded in HDR mode normally contain unchanged sensor data and thus are of linear Gamma. There is a setting among SilverFast's options however that will let HDR scans get gamma encoded just like ordinary scans. To avoid this you'll need to make sure that the checkbox "for HDR output" next to the "Gamma-Gradation" field on the options' General tab is left unchecked.

Some options that can exclusively be executed during scanning itself will remain active when operating in HDR mode though. One such option is the automated removal of dust and scratches via Digital ICE. If you want to use this on your Negatives you can do so. When scanning color negatives it is also advisable to consider the use of multi sampling. That is if this is supported by the particular scanner hardware you possess.

Improving quality by use of analog gain

For some scanners further options on the special tab can be of interest. If you are using an older scanner model which supports the adjustment of lamp brightness / exposure time for the individual color channels which is often referred to as analog gain you can utilize that to reduce the orange mask of a color negative during scanning or even to eliminate it altogether. An example for scanners allowing you to do this is the Nikon Coolscan series. In a typical linear scan of a color negative the blue channel is more than two exposure values below the red channel and the green channel often is more than one EV below it. For modern scanners with 16-bit/channel precision this often is irrelevant for inverting the negative as there is still enough detail to work with. For older scanner models with 14-bit precision or even only 12-bit precision equalizing the three color channels’ lightness before analog/digital conversion can improve the quality of the inversion. If we consider that the blue channel typically is the least detailed portion of the scan we can observe that it is possible to bring its quality up to the level of that of a scan with 2-bit/channel more precision. In SilverFast you can use the option lamp brightness which is on the option’s special tab to bring up a dialogue to manipulate these settings. It is noteworthy however that often the lamp brightness can’t be increased any further. In case of the Nikon Coolscan scanners exposure time will be lengthened instead. It is conceivable that for other scanner models an analog amplification of an electric signal might be used which would most likely not lead to the desired improvement. Using this feature with any scanner will require a series of tests.

Removing banding effects in the scan e.g. for the Nikon Coolscan LS-8000

If your scans are showing stripes that do not run in the direction the CCD moves, as can result from dirt in a scanner and you scanner has more than just one CCD line the option Super Fine Scan which is also located on the option’s special tab can resolve the problem. This is a known issue for the Nikon Coolscan LS-8000. Super Fine Scan will lead to using just one of the scanner’s three CCD lines since using all three is what results in the banding effects. This will considerably slow down scanning but it removes the annoying effect that negative scans are especially prone to. The banding usually occurs in dark tones but becomes a banding in light tones after the inversion which is much more obvious. Due to the frequency of this being a problem we operate our Coolscan LS-8000 exclusively in Super Fine mode. For the current generation of scanners Nikon is said to have solved this issue so that you can use the scanner’s full speed without dramatically impairing quality.

To conclude we'd like to thank our user Frank Ludvigsen cordially for providing us with the screen shots of the english SilverFast SE interface on Mac OS X used here.