IT8 Calibration - Compression of Grayscale

flatbed scanners for Epson

bosveldboer
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Joined: Wed Jan 02, 2013 1:19 am
Scanner: Epson 4990
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IT8 Calibration - Compression of Grayscale

Postby bosveldboer » Thu Mar 07, 2013 5:36 pm

Hi,

I calibrated my Epson Scanner 4990 with IT8 calibration with a Reflectuive target and the Release r21 of Silverfast 8 Ai Studio on OSX.
I then scanned the calibration target colour squares in 48 with the new calibration profile, but noticed that the grey scale (Histogram) is still compressed and does not make full use of the available range.

The Black Point is around 15 instead of 0 and the White Point is around 230 instead of 255. That means I need to manually adjust the Histogram each time I do a scan.

What is the reason for this compression during the calibration, as I thought the calibration will adjust the scanner profile to make full use of the range of the scanner?

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LSI_Ketelhohn
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Re: IT8 Calibration - Compression of Grayscale

Postby LSI_Ketelhohn » Tue Mar 12, 2013 9:37 am

Dear customer,

There is no compression.
The grayscale in the target simply does not contain the value you expect.
There are no 0/0/0 255/255/255 fields on the target due to technical reasons.


kind regards,
Arne Ketelhohn


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