Re: OT: 16 bit editing myth or reality?
Yves, I understand you like statistics, but the scope of your problem is entirely deterministic other than you assumed the input signal to have normal distribution yesterday. Your manipulation, quantization and evaluation of the mean square error are completely deterministic. I do not agree about the normal distribution assumption. Almost no image I edited had anything like normal distribution. Tails are usually much much thicker than normal. Many of my images look more closer to uniform than normal, with multiple local peaks, skewness, etc. that are not a feature of normal distribution. Normal distribution is seen in many places in nature where the observed quantity is an aggregate results of many small factors. However, image pixels in usual pictorial photography are not this type of statistic. I also do not agree that mean square error is the best measure for the error for your study. From: Yves Gauvreau <gauvreau-yves@cgocable.ca> Subject: Re: OT: 16 bit editing myth or reality? Date: Mon, 17 Dec 2007 06:15:27 -0500 > Ideally, this would need to be done on more then one image, > 30 or more would give us what is called a confidence > interval that the difference is or is not significant based > on the (variant) CIE dE method I used. No, you wouldn't need to do that. Since everything is deterministic, all you need is a reasonable assumption for the density function for the input data. You can make it up or empirically obtain this using any of the density estimation techniques. Then the error measure can be obtained numerically (or analytically, if you keep things simple) with deterministic certainty. Now I like to add that the results obtained above will be sensitive to the choice of numerical manipulation to the image, quantization method and presence of small noise added to the input. Furthermore, the issue becomes more complicated when spatial dependency of the input statistic as well as the manipulation is considered. Such is the reality in image processing. If your debate was 12-bit vs. 16-bit, the conclusion may be a matter of judgement. But between 8 and 15 or 16 bits, I think the practical decision is a no brainer. -- Ryuji Suzuki "I can't believe I'm here. People always say that I'm a long way from normal." (Bob Dylan, Normal, Illinois, 13 February 1999)
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