The 'right' way to do it is to scan the GS patches and look at the histogram of each color channel (A good-looking histogram looks like a picket fence. Less-good histograms look like uneven heaps of sand). Tweak the scanner's settings to get the best looking histograms on all channels. Use these settings to make your profile and do your scanning.
A fast and dirty method that will probably cut your max dE in half is: Set shadow to 0, highlight to max. Adjust gamma to get RGB values of GS11 as close to 100 as you can. Use these settings for profile and scanning. Realistically there is no data at the extremes and you could get slightly better results by moving the shadow and highlight in a bit. Figuring out how much leads you to the histogram approach. Because you have made the scanner's color space as big as possible, the scans probably will look washed out without the profile. It's the CMS's job to make the image look right on your chosen output device. Note that this gives you a profile that works for "good" images. If you were scanning very dark or very light images you'd want to set the scanner up to use more of the scanner's range on the values that are actually in the image, then make a profile for these special settings. In the raw image histogram you would try to get the values to spread throught the range rather than being bunched at one end. The general idea is to get as much information as possible from the original image into the scan. Use the scanner to capture data. Use your image-processing software to correct the image. > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Peter Gregson > Sent: Thursday, August 07, 2003 9:52 PM > To: [EMAIL PROTECTED] > Subject: [Lcms-user] expected dE values > > > What are reasonable values for dE when using an Epson 3200 Photo scanner > and the Wolf Faust reflective targets? I have an average dE of 1.39, > but a peak dE of 15.94, for colour patch J4 on the target. I have a > number of dEs of 5 as well, usually in the yellows. Is this unreasonable? > > Thanks, > > Peter Gregson > > > > ------------------------------------------------------- > This SF.Net email sponsored by: Free pre-built ASP.NET sites including > Data Reports, E-commerce, Portals, and Forums are available now. > Download today and enter to win an XBOX or Visual Studio .NET. > http://aspnet.click-url.com/go/psa00100003ave/direct;at.aspnet_072 > 303_01/01 > _______________________________________________ > Lcms-user mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/lcms-user > ------------------------------------------------------- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa00100003ave/direct;at.aspnet_072303_01/01 _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user
