If you purchased the CD-Rom version of SilverFast rather than downloading application from the LaserSoft web site you will find two versions on the disc. One is a Photoshop Plug-in and the other a Twain module. Currently the Twain specification does not support full colour management and so this tutorial will concentrate upon the Plug-in version of SilverFast.
Download the Adobe PDF Version of this Tutorial
Note: the screen-shots are all based on the Mac OS X version of
SilverFast Ai/HDR, although the layout of the various dialogs for the
Mac and Windows platforms is virtually identical.
Before getting into IT8 calibration let's have a quick overview of
the SilverFast Tool Bar and Palette. Some of the buttons on the
Preview Window will only be present on certain scanner models. By way of example - the
Film Format button only appears when the user inserts a film carrier designed to hold multiple film formats. Examples of such a scanners are the Polaroid SprintScan 120 and Nikon 8000. When the multi-format film carriers the actual film format must be selected manually by toggling the button until the format you require is shown.
Special Functions Button Bar
SilverFast Adjustment Tools Palette
LaserSoft provide a lot of helpful information on colour management within
the user manual and much of this is replicated on a dedicated PDF file (SF IT8 Manual) to be found in the
SilverFast IT8 folder on your hard disk.
Unfortunately it all relates to SilverFast Version 5 and so users of
Version 6 can easily become confused. Nevertheless, if you haven't already read these documents I recommend that you do
as there are some quite useful information.
Also, if you are in any doubt as to how the SilverFast colour management
system works it might be worth reading the SilverFast
CMS Settings tutorial which has also been revised to reflect the
changes introduced with SilverFast 6 release r37 and upward. Actually with version 6 LaserSoft
have taken the opportunity to standardise all of the colour management
dialogs across the full range of products so the following tutorial
also applies to SilverFast SE, DC, DC Pro and
PhotoCD
Figure 1 - SilverFast Frame Window
Ideally, the Frame window should be configured so that the Filter and
Image Type are as shown above. The Scan Type/Mode can
be set for 36 ->24 Bit Colour (if calibrating a scanner) and
48 Bit HDR Colour (if scanning an IT-8 target to calibrate SilverFast HDR).
We also want to set SilverFast for our preferred gamma-gradation
value; between 2.0 and 2.2 seem to be the optimum range. Press
Option, select
the General tab and insert the required gamma-gradation value. A short tutorial explaining a method for determining the optimum
gamma-gradation value can be found
here.
Figure 2 - Configuring
Gamma Gradation
The purpose of the: for HDR output checkbox is to enable raw
gamma corrected 48 Bit HDR Colour images to be scanned. The
image will therefore be scanned with the gamma value already applied to
the image but no other corrections are allowed. I suggest that you only use this feature when you want to scan images
directly into Photoshop.
Whilst activating the feature will have no detrimental effect on the
scan but it can present you with a few additional steps (see note below) if
you're intending to use/calibrate SilverFast HDR.
Note: SilverFast HDR has an additional insertion box labelled
Gamma expected in 48Bit/HDR data. The purpose of this checkbox is to enable the user to insert
the gamma value already incorporated into the image file. It is used to apply an inverse gamma curve
which cancels out the gamma of the image and thus prevents the application of a double gamma adjustment. By way of an example -
had you scanned your image in SilverFast Ai with for HDR output
active and at a gamma of 2 you would need to insert 2 into the
Gamma expected in 48Bit/HDR box.
Gamma Gradation in SilverFast
HDR
The above screenshot shows the SilverFast HDR setup required
for the settings I recommended in Figure 2 above. The chosen Gamma-Gradation
value reflects the gamma that I want to use for my FINAL image.
The value quoted in the Gamma expected in 48Bit/HDR data input field is the EXISTING
gamma-gradation value embedded into the raw scan from SilverFast
Ai by virtue of the for HDR output checkbox NOT being
activated.
Although not absolutely essential I usually recommend that all colour management features
are set to
Off. This can be achieved by selecting the CMS tab in the
Defaults window. The following is how I recommend that the dialog should
be configured.
Figure 3 - Disabling
Colour Management
Ideally, you'll will want all the pop-ups to read None and checkboxes to be deactivated before running the
IT-8 module. This is especially important if you're scanning the IT-8 target for use with
SilverFast HDR.
Contd.
12 August 2003
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