7500i calibration IT8

All the problems with Plustek film scanners

Apolinaire
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SilverFast Product: Ai Studio
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7500i calibration IT8

Postby Apolinaire » Mon May 18, 2009 10:04 pm

Hello everybody,

Here is my configuration : Plustek 7500i with Silverfast Ai Studio. My OS : Windows XP Pro SP2. My screen is calibrated with Spyder2 Pro Studio.

When I calibrate my 7500i with the 35mm IT8 calibration target, the image on the screen is very nice. See hereafter the screen shot.

Image

But immediately, Silverfast makes a prescan and hereafter is what I obtain :

Image

I'm not satisfied. White is not white and the other colors don't match. It seems that the created profile icc is not active.
So I looked for it in C:\WINDOWS\system32\spool\drivers\color and I found 3 icc profiles and 1 icm profile for the 7500i :

Image

But when I try to choose in Silverfast /Options / CMS panel, I find only the icm profile and not the others icc...

Image

What does it mean ? Where is the profile created after calibration ? Is it in the icc files ? And when I reset Silverfast (Shift - S - F +start in SFLauncher or reset the factory settings in Options / General) why does the CMS setting become SFprofT (Plustek OpticFilm 750) ?
There are some things I don't understand between icc and icm profile and the factory settings.

Is my monitor profile created with Spyder2 Pro Studio can interfere with my Plustek scanner settings ?
it's incomprehensible !

Thank you very much for some explanations.
Apolinaire

LSI_Muenier
SilverFast Expert
SilverFast Expert
Posts: 351
Joined: Wed Feb 13, 2002 1:00 am

Re: 7500i calibration IT8

Postby LSI_Muenier » Tue May 19, 2009 7:38 am

Dear Apolinaire,

the IT8 calibration analyzes the RGB image data of the IT8 chart as acquired from the scanner and compares them with the data found in the reference data file (obtained at LSI by spectral measurement of the IT8 chart). During calibration, an ICC profile is generated that converts the scanner-acquired data into the reference ones.

It is NOT the goal of the IT8 calibration to convert the Dmin area (i.e. the one at the left end of the gray scale) to pure white (RGB=255), because this could lead to loosing details in highlights -- think of a slide that contains a lighter colour than this Dmin area! Therefore, SilverFast produces an ICC profile that maps the Dmin to the reference value (e.g. L=88) so that lighter colours are scaled into the remaining highlight range up to RGB=255. Equally, the gray scale is mapped to the reference values which are not all purely neutral, but close to neutrality.

The IT8 calibration maps the scanner RGB values to the reference values as a common correction to all your slides.
Please use the tools in SilverFast (Image Automatic, Histogram, Gradation dialog) to perform:
- the expansion of the slide's limited color range to the full RGB range,
- midtone correction (both of this is done by the Image Automatic),
- possibly further gradation corrections if the current image needs it
individually for the image slide you want to scan.

The SF_T profile is the one generated by the IT8 calibration, the SFprofT is a default profile installed by the SilverFast installer.

Best regards
Martin

Apolinaire
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Posts: 4
Joined: Mon May 18, 2009 9:14 pm
SilverFast Product: Ai Studio
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Re: 7500i calibration IT8

Postby Apolinaire » Tue May 19, 2009 8:00 pm

Hello,
Thank you very much Martin for these explanations. My understanding of calibration is better now.
Apolinaire

Curt Wiler
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Joined: Sun Nov 22, 2009 2:05 am
Scanner: Plustek 7500i, Epson 4990 Photo
SilverFast Product: Ai
SilverFast Version: 6.6

Re: 7500i calibration IT8

Postby Curt Wiler » Sun Nov 22, 2009 2:13 am

Following up on this thread, the manual says the user should be able to name the calibration file. My program is not giving me a chance to do this, it just verifies the calibration was successful. So, while I can verify (by the time stamp) that the calibration has been stored as The SF_T profile, how do I go about storing profiles for different films, especially Kodachrome, when I get other targets?

LSI_Morales
SilverFast Master
SilverFast Master
Posts: 1430
Joined: Mon Oct 22, 2007 9:33 am

Re: 7500i calibration IT8

Postby LSI_Morales » Mon Nov 23, 2009 12:33 pm

Dear Wiler,

The option you want to use is only available in SilverFast Ai or Ai Studio. This can be found under "Options/Auto" and marking the checkbox next to "Custom ICC profile name" See the next picture.

Screen shot 2009-11-23 at 12.28.50 PM Kopie.png
Custom ICC profile names
Screen shot 2009-11-23 at 12.28.50 PM Kopie.png (58.66 KiB) Viewed 4115 times


Cheers
Alejandro Morales

LaserSoft Imaging
Media manager, Software testing


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