Thread: [Lcms-user] Re: Lcms-user digest, Vol 1 #253 - 1 msg
An ICC-based CMM for color management
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From: Jeff H. <jh...@co...> - 2003-08-27 05:34:38
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<<< I post the following for Don Hutcheson, creator of the HCT, in response to some recent posts by Wolf Faust>>> ....................................................................... I don't know where Wolf Faust gets his data from but there is overwhelming evidence from real-world, high-end scanner and digital camera users that the HCT does a better job than the IT8. As for his claims that I'm just creating extra patches for marketing value, he's sorely mistaken. The current HCT design is the product of about eight year's research and experimentation, with all available profiling packages and dozens of different scanners. In fact I started out with a 250-patch design where I simply re-occupied the IT8 patches with different colors. (Didn't produce enough improvement). Interestingly, I never planned to commercialize the HCT. I created it just for my own use and for my own consulting clients. I was forced to go public with it through word-of-mouth testimonials and strong user-demand. As for Faust's claims that only 170 patches are necessary to create a good scanner profile, that's a theoretical dream. It's like saying a 300-patch printer target can do the same job as a 1400-patch target. (I wish!) Sure, if you already know the basic characteristics of a particular scanner model and if that scanner applies absolutely no color transform except the normal 1-D curve functions, you would (theoretically) only need a few 'hinting' patches (less than 170, by the way) to create a good profile. But in reality, all scanners work differently, often with annoying little non-linearities in unexpected places. And individual scanners within a family are usually different enough that most modeling theories can only make an approximate prediction, not an exact analysis, of a certain scanner's characteristics. Multiply this by the enormous number of variables in the typical user interface and you can see why many more than 170, 250 (or even 500, for that matter) patches may be needed to successfully decode the performance of any particular scanner for which you do NOT already know the basic characteristics. An even worse case is if a scanner applies any color transformation like a 3xn matrix, a 3-D LUT or an ICC profile (which many do). In that case even 500 patches will probably be too few to successfully analyze that scanner's RGB color space accurately. In spite of all this, I am happy to say that I have achieved quite good results with some IT8s on some scanners (using my 'extended profile' trick) and, as I have always said, casual users should be quite satisfied with the IT8. But high-end users continually tell me the HCT blows the IT8 away for critical matching to the original. The differences they notice are usually in deep colors and shadow tones and the reasons are pretty obvious when you compare the IT8 to the HCT. The bottom line is that to do the best possible job you have to start with the best possible tools. Any way you look at it, a hand-measured 500 patch target is quite obviously a better tool than a hand-measured 250 patch target. Period. I'm copying this to Dr. Chris Edge (KPG-Imation) - one of the world's most experienced and respected color scientists. Chris tells me his tests show the HCT clearly improves the quality of scanner profiles compared to profiles from the IT8. That, along with many unsolicited letters of thanks and congratulation from demanding color separators and photographers over the last two years is good enough for me. Regards, Don ****************************** Don Hutcheson Hutcheson Consulting (Color Management Solutions) 11 Turnburry Rd Washington, NJ 07882 Phone: (908) 689 7403 Mobile: (908) 500 0341 Fax: (908) 689 5305 E-mail: do...@hu... ****************************** |