SilverFast 6 Ai & HDR

SilverFast Box

Tutorial - 1

 Basic steps to IT-8 Calibration

By Ian Lyons

 

12 August 2003
 

LOGO

A Computer Darkroom Tutorial

One of SilverFast's greatest selling points is the fact that it remains one of a very few scanner applications that allows for a fully colour managed workflow within Photoshop. Nevertheless, getting colour management set up correctly can be somewhat daunting for the new user. This tutorial is intended to show how to configure the SilverFast IT-8 calibration module for optimum image quality.

 

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.

 

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.

 

Preview Screen Buttons

Special Functions Button Bar

 

SilverFast Tools

SilverFast Adjustment Tools Palette

 

Configuring the IT-8 Calibration Module

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

 

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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).

Step 1 - Getting SilverFast ready for calibration

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.

 

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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.

 

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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.

 

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